Digital Agenda for Europe
A Europe 2020 Initiative

Quantum technologies – how to make quantum technologies a reality?

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Technologies that exploit quantum phenomena like superposition and entanglement will be a radical departure from current technologies. Several promising directions are now well known, for instance in computation, communication, security, metrology, sensing, simulation and material science. Europe has the scientific lead in many of these, and some European companies were first to market with some concrete applications of quantum technologies (quantum key distribution in particular). Building on such successes is it not time to bridge from the science to the engineering of some more concrete quantum technologies? For example, are we close to delivering a quantum simulation technology, and if so what precisely will it simulate? Or can we start to concretise the necessary quantum-ware for large scale quantum networking? What about applications in biology and medicine?

What are we looking for?
•    What should be the orientation of research on this topic? As stated, do you feel it is too broad or, on the contrary, too narrow?
•    Have any recent scientific results been obtained relevant to this topic? Is there already a well-established community on this?
•    Do you know of related initiatives, for instance at national level, or in other continents?
•    What is needed at this point to advance this? More exploration of different ideas? More coordination among groups or related initiatives? A strong push for a precise technological target and, if so, which one? Anything else?

Background: Following the last FET consultation during 2012-13, 9 topics were identified as candidates for a FET Proactive. This topic has been selected in part for inclusion in the FET Work Programme for 2014-15. Comments are invited on whether this topic is still relevant, or if any changes would be necessary to take account of recent research results. We are also trying to understand better how to advance these areas.

To participate to the consultation:
- register to the group (create an ECAS login if you don't have one yet);
- then "log in" and enter your contribution in the "Add new comment" box, at the vey bottom of the page.
You can also participate by commenting on submitted ideas and/or voting for them.

If you wish to share with us additional documents or have any questions about the process, please send them to our FET mailbox.
 

 

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Sophisticated recent experiments with ultrashort laser pulses support the idea that intuition-defying quantum interactions between molecules help plants, algae, and some bacteria efficiently gather light to fuel their growth.
Researchers flash laser pulses at the light-harvesting protein molecules of bacteria and algae, timed to within a billionth of a billionth of a second, then observe how the energized molecules re-emit light of different colors in the ensuing instants. This allows investigators to deduce how energy is stored by and moves among the molecules. But the results would be impossible to explain if captured light energy were conveyed by discrete entities moving randomly between molecules. Rather, the insights of quantum mechanics are needed.

http://rsif.royalsocietypublishing.org/content/11/92/20130901.short?rss=1

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Quantum systems in Nature typically evolve according to local Hamiltonians,
and in particular, cooling such a system to low temperature" allows the system to relax
into its ground state. Thus, understanding the solutions" (i.e. energies and eigenvectors)
to quantum constraint satisfaction problems is central to understanding the structure and
behavior of the physical world around us.
Quantum Hamiltonian complexity provides new approaches and techniques for tackling
fundamental questions in condensed matter physics, in particular the classical simulation
of quantum many body systems.

http://simons.berkeley.edu/sites/default/files/uploads/ucberkeley_qreadi...

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Improving our conceptual understanding of quantum electron transport at the nanoscale is needed for enabling the emergence of “Beyond C-MOS“ nano-electronics devices. This implies a combined effort in the topics of spintronics, molecular electronics, single-electronics, quantum dots and nanowires, nano-cooling. Rapidly-progressing studies on Quantum Nano-Electronics rely on state-of-the-art technologies of nanofabrication, electron and near-field microscopies, transport measurement under extreme conditions (low temperatures, magnetic field, radio-frequency irradiation) and theoretical calculations.

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A large number of interesting demonstrations with optical systems have been realized for the exploitation of purely quantum phenomena for quantum information or quantum computing. However, the scalability of such systems remains a problem. It is therefore important to study quantum transport and quantum technologies in electronic circuits and devices, where the up-scaling may be less of a problem.
Although recently a machine consisting of nearly 100 electronic quantum circuit elements was presented, it is far from clear that the computations are really quantum in nature (http://physics.aps.org/articles/v6/105), and it is clear that fundamental studies are still essential. We need to learn more about decoherence processes, and how to increase the quantum coherence in electronic circuits; about new materials and hybrid systems, which can be used (e.g. spintronic devices, molecular electronics, single-electronics, quantum dots and nanowires, superconducting circuits and hybrid supra / semi / magnetic systems); and about other mesoscopic phenomena, such as quantum heat transport and nano-cooling.
In Europe today there exist a very vibrant community in mesoscopic physics, which has contributed to a number of recent relevant scientific results, such as the realization of electronic qubits, and the improved understanding and manipulation of quantum coherence in electronic circuits.

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Thermoelectrics denotes, in a broad sense, the conversion of heat into electricity (the Seebeck effect). Interestingly, it also includes the reverse phenomenon (the Peltier effect), i.e., the generation of heat fluxes upon the application of electric currents. Therefore, progress in waste heat capturing would inevitably lead to improvement of thermoelectric cooling and refrigeration techniques.

Conversion efficiency is described with the aid of the ZT factor of merit. So far, the values achieved for ZT fall short of those required for wide technical use, motivating the need for a fundamental approach to lay the basis for future improvement of devices and materials for broad applications. Nanostructures offer not only promising enhancements of ZT factor but also novel thermoelectric functionalities due to their lower dimensionality and the large variety of well characterized nanosystems at our disposal. Furthermore, fundamental questions arise from the interplay between quantum coherence, quantum confinement and strong interactions in mesoscopic conductors subjected to both external electric fields and thermal gradients.

More specifically, thermoelectric quantum transport deals with solid-state systems effectively formed in 0D (quantum dots), 1D (nanowires, quantum waveguides), 2D (graphene and quantum wells) and 3D (superlattices and multilayers), as well as in molecular junctions. Of interest are nonlinearities, chaotic scattering, time-dependent fields and the influence of superconductivity (hybrid systems) and spintronic effects. This is an exciting field with an enormous interest for the European community.

http://iopscience.iop.org/1367-2630/focus/Focus%20on%20Thermoelectric%20...

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Should FET take account of Member State Initiatives in this area and work out what might add value at a European level? The UK has called for a national network of quantum technology hubs with funding of £155m. The website is here: http://www.epsrc.ac.uk/newsevents/news/2014/Pages/quantumtechnology.aspx and they anticipate hubs in the following areas:
Quantum Secure Communications
Quantum Metrology
Quantum Sensors
Quantum Simulators
Quantum Computation
I guess other member states will have similar programmes either in planning or operation. Since this topic is technology centred I guess it would be useful to attempt to coordinate European effort if this is possible.

Another possibility is a shift in focus to emphasise more the application of the expected technologies in some challenge areas. For example, I guess there are many issues of how to harden current security measures so they are resistant to attacks utilising quantum technologies. This is probably very challenging and multidisciplinary while also being of vital importance to both the public and private sector.

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Micro-Nano-electronics will face severe limitations in terms of power consumption and variability at scale below 5-10nm. This should appear around 2026 according to the ITRS roadmap. Revolutionary concepts are needed and what else except quantum concepts & technologies? We should work now on solid state electronic devices exploiting a broad range of concepts inherited from atom physics, superconductivity, quantum optics,.. and relying on the best available materials and nanofabrication skills in Europe.

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Quantum electrical circuits, in particular superconducting quantum circuits, offer a broad range of opportunities for developing quantum technologies with a sizeable potential impact. Here are some research directions in this field. It is worth noticing that the US are presently heavily pouring manpower and funding. The hype is now even reaching a broad audience. To go or not to go, that is the question for Europe. Better not to miss the second quantum revolution.

-Quantum limited amplifiers based on parametric amplification allow to measure an individual quantum system with a minimal backaction corresponding to the amount of information taken. This makes possible the detection of a single spin, ESR on a single molecule, .... These amplifiers may also find their way in astronomy. Note that BICEP2 has used SQUID detectors, although not operated at the quantum limit. Startups are considered in the US, but not in Europe (as far as I know).
-quantum electrical circuits have open the field of quantum microwaves. The foundational quantum optics experiments recently performed with electrical circuits indeed demonstrate that microwave photonics is a reality . Applications will be envisioned once the toolbox developed enough.
-quantum information processing with superconducting processors have already demonstrated the speedup of quantum algorithms (in elementary situations) and important protocols (teleportation,...). Although the scalability issue is not solved yet, it is clear by now that larger platforms can be developed.
-The academic community worldwide is developing quantum processors based on the unitary evolution of a register. This route is difficult, and only tiny processors have been operated. The DWave company that is following the Adiabatic Quantum Computing route, claims that decoherence and thermal excitation issues do not affect the quantum power of their machine. Note it is already able to solve non trivial optimization or machine-learning problems. Resolving this coherence issue is very important and the answer will affect the future of the domain. What each strategy can deliver for QIP is a major issue to be sorted out.

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Quantum technologies offer the possibility to enhance the performance of existing systems in addition to generating new sensing and imaging techniques beyond those available in classical devices. The future emerging technologies that will be enabled by studying Quantum Technologies and the Interaction of Light and Matter offer the potential of transformative new technologies in the global challenge areas of security, healthcare and environmental monitoring.
Several ultra-sensitive displacement sensors, based on interferometric measurement, are/will dominated by quantum noise across the majority of their operating bandwidth (GEO-HF: http://www.geo600.org/1037150/GEO_High_ Frequency, Advanced VIRGO: https://wwwcascina.virgo.infn.it/advirgo/). Quantum noise occurs both at the large scale, such as in these long baseline gravitational wave detectors, and also at the millimetre scale, such as table top prototypes and cavity opto-mechanical experiments (http://www.cqom-itn.net/). Quantum technologies, based on squeezed states of light, promises the reduction of the quantum noise in a wide frequency range (both in shot noise and radiation pressure) by up to an order of magnitude. To achieve this target requires a series of developments in the area of optical technologies including low loss optical mirror coatings, new dielectric sputtered/expitaxially grown optical coatings and structured coating free mirrors, novel control techniques with high optical powers (optical springs) and the development ultra low noise, high stability, optical reference cavities.
There are strong links to established international collaborations within these areas including the International Max-Planck partnership (http://www.epsnews.eu/2014/ 01/first-impp-by-scots/), and Optical Frequency and Metrology standards (http://www.mpq.mpg.de/~haensch/comb/). There further exists high potential for cross field collaboration, where techniques can be further applied to future emerging technologies including;
• squeezed light sources for biological imaging
• imaging beyond line of sight with entangled systems
• aberration free imaging
• monitoring of temporal gravitational fields and single photon detectors with the visible-IR bandwidth.
• high damage threshold coatings for laser mirrors
• narrow band optical filters for fluorescence microscopy
• development of high sensitivity accelerometers based on both atom interferometry or classical MEMS, which are readout with sub-shot noise interferometric readouts
• highly specific gas sensors and compact Raman spectrometers.
There is significant potential for novel sensing at and beyond the standard quantum limit which can be enabled through the expertise that exists across various institutions and companies within Europe.

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Semiconductors are the material of choice for conventional information technologies, and recent studies strongly indicate that they have large potential to also become the basis of scalable quantum technologies. Encoding quantum information in the spin of electrons (and in some cases atomic nuclei) in semiconductors allows for long-lived quantum coherence and fast control. The highly-developed tools of semiconductor micro-fabrication open up the possibility transform these systems to technologically relevant scales. While this is, e.g., greatly interesting for applications in quantum simulation, it actually has implications beyond this, i.e., for quantum information processing and quantum technologies in general (the quantum simulations call in the previous round of FET dealt with an important sub-topic and was highly welcome, but was too limited to cover this relevant and more general topic). The apparent limitations of the electron spin coherence due to the hyperfine coupling to nuclear spins (mostly in the otherwise high-quality III-V semiconductors) has recently lead to a number of scientifically interesting approaches, among them the study of new and different semiconductor materials, such as silicon and silicon-germanium (http://www.nature.com/nature/journal/v481/n7381/full/nature10707.html, http://arxiv.org/abs/1402.7140, http://arxiv.org/abs/1404.5402 ), as well as new ideas in controlling and monitoring the magnetic environment of a spin qubit (http://www.nature.com/nphys/journal/v5/n12/abs/nphys1424.html, http://arxiv.org/abs/1405.0485 ). There is a strong and well-established community striving for the development of knowledge and technologies based on semiconductor-based quantum information (see, e.g., Annu. Rev. Condens. Matter Phys. 4, 51 (2013); http://www.arxiv.org/abs/1204.5917 and Rev. Mod. Phys. 85, 961 (2013); http://journals.aps.org/rmp/abstract/10.1103/RevModPhys.85.961 ). Further materials systems that open interesting scientific avenues are carbon-based semiconductor systems such as graphene, carbon-nanotubes, or diamond (with defect spins), as well as semiconductors with strong spin-orbit coupling (InAs, InSb, etc.) and semiconductor-superconductor hybrid systems where cavity-QED and new quantum-mechanical quasiparticles (anyons, Majorana fermions) with exotic properties and potential applications for quantum information can be found. Spins in semiconductors –if they can be interfaced with photons—would be ideal quantum memories for quantum communications tasks in a quantum network (e.g., in quantum repeaters). These approaches bring up completely new scientific questions related to novel materials and quantum phases that they support. Along with strong efforts towards scaling-up the working spin-qubit schemes, these scientific questions need to be explored.

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Silicon is a highly attractive material for quantum information processing and spintronics as it provides an environment where spins can be controlled with minimal decoherence and because silicon CMOS technology dominates today’s microelectronics industry. Inspired by Loss & DiVincenzo's seminal paper on spin quantum bits [Physical Review A 57 (1998)], Kane’s follow-up paper on silicon-based quantum computing [Nature 393, 133 (1998)] triggered an exponential growth in the interdisciplinary field of quantum information in silicon, but it is only in the past year that experimental demonstrations of spin control and measurement in silicon have been achieved – see, e.g. Morello et al., Nature 467, 687 (2010); McCamey et al., Science 330, 1652 (2010); Greenland et al., Nature 465, 1057 (2010). In all of these experiments phosphorus dopant atoms served to localise the electron spins. Silicon quantum dots provide full tunability of tunnel rates and spin coupling that is possible using e.g. multi-gated silicon metal-oxide-semiconductor (MOS) nanostructures.

The strength and popularity of silicon quantum electronics is underlined by these two recent review articles:
http://journals.aps.org/rmp/abstract/10.1103/RevModPhys.85.961
http://www.nature.com/nature/journal/v479/n7373/abs/nature10681.html

This booming field must not be missed within the EU.

Floris Zwanenburg
Assistant Professor
University of Twente

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Quantum computing research is progressing fast on a global scale and starts making a transition towards engineering and industry outside Europe. Globally, the field of Quantum Technologies (QT) is entering a stage where large resources are put into engineering of devices and systems in a quest for ground-breaking applications in quantum computing, simulation, and communication. The competition is becoming fierce, and major resources are invested in USA, Canada and Japan in powerful collaborations to achieve breakthroughs in fault-tolerant computing. The concept of "The European Dimension", i.e. fairly loose EU collaborations without adequate funding at the R&D level, is no longer enough to stay competitive in the QT field. Europe is already falling behind.

Superconducting circuits (specifically transmon-cQED with coherence times in the 100 microseconds range) are now being scaled up to systems with 10-20 qubits and beyond. Europe is in the very frontline when it comes to fabrication and operation of small experimental systems, aiming for 10 qubits within 1-2 years. However, the next step, scaling up to 20+ qubits will involve an engineering effort requiring orders of magnitude larger resources than presently available. Moreover, it will require training of a new kind of engineers, and it must involve industrial fabrication.

In Europe we must therefore urgently face the question of how to create a sustainable development of quantum information processing (QIP) and communication, and how to provide the resources for scaling up QT platforms, both solid-state and AMO ones.

To this end it is necessary to realise that we are ultimately talking about focused efforts at the level of a flagship - a QT Flagship - with strong commitment from industry and national funding agencies. A limited proactive programme during 2016-17 can certainly contribute to many exciting achievements, but cannot define a > 10-year QT strategy and provide the corresponding funding - this will take a QT Flagship, or a comparable effort. A QT Flagship will no doubt be needed in order to be able to engage and develop European industry and to create a unified approach involving national funding agencies. A QT Flagship will also be able to include and integrate a variety of fundamental quantum research activites in purposeful way.

An important aspect of QT is high-performance computing (HPC). It is obvious that running quantum computers and simulators will involve classical frontends and processing, and in the future, quantum processors will most likely in practice be accelerators embedded in classical HPC (cHPC) systems. Nevertheless, for efficiency, the classical integration needed should be developed within (or directed by) a QT Flagship, and there is no clear foundation, within the foreseeable future, for QT-cHPC project integration.

New computing paradigms are required for information processing including, for example, neuromorphic computing, quantum computing, chemical and molecular computing, quantum computing by molecular spin clusters and bio-inspired computing, among others. Solid-state quantum computing and neuromorphic computing could become embedded in digital environments via digital-analogue hardware and software interfaces. The target would be to create useful hybrid systems capable of adaptive learning.

Actually, recent QIP development makes use of quantum neuromorphic algorithms (classifiers) for machine learning involving optimisation and pattern recognition in big (quantum) data bases. This underlines that a QT flagship needs to incorporate a broad field of computer science.

Finally there is the issue of the D-Wave Systems company: D-Wave has developed several systems of 512 superconducting qubits used for quantum annealing (analog computing; optimisation), a 1000 qubit system is in the pipeline, and 2000 qubits in the near future. D-Wave is supported by venture capital, Google, NASA, NSA, Lockheed-Martin, .... and has sold 2 machines to Lockheed-Martin (placed at USC) and to NASA-Ames. Google is developing software for optimisation, and testing the machine. The machines currently basically do not outperform classical PC-machines with optimized annealing software, but the superconducting technology is groundbreaking, and the scaling-up is "easy", because the qubit arrays are not coherent. (See also the comments by Daniel Esteve). Time will show whether the D-Wave machines are worth the money. The bottom line is that D-Wave represents a kind of entrepreneurship that simply does not exist in Europe, but efforts at that scale, or larger, are essential for QT-Europe to prevail. A QT-flagship would have to be the European way to go, because venture capital and industry involvement at the needed scale do not exist in Europe at the present time. It should be noted that D-Wave has worked during 10 years to reach its present level. In Europe, it seems that the EC and public funding must lead the way via a QT-flagship that then can develop the needed commitments and funding in a relatively short time.

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Significant investment in quantum technologies within Europe and elsewhere has led to rapid progress in the field. Therefore investment in quantum technologies as a FET Proacitve has the potential to convert this previous investment into mature technologies that can be commercialized. A number of physical implementations have reached maturity in terms of all DiVincenzo criteria. In order to develop real world quantum computers and quantum optimisation devices it is critical to invest in the further development of mature quantum implementations, so they can reach a product development phase. Fault tolerant performance is important for most quantum devices. In order to utilize quantum operations without the need of excessive resources, quantum gates need to be well above the fault tolerant threshold. Furthermore, it will be important to produce and characterize large entangled states. Therefore I propose the following two key areas for targeted funding.

Pushing quantum gate well above the fault tolerant threshold:
Robust quantum gates with entanglement fidelity well above the fault-tolerant threshold will be critical for numerous quantum technologies, such as computing, sensing and simulation.

Creation, validation of and verification of large entangled states:
Large entangled states incorporating many qubits will be required to carry out quantum algorithms. The efficient creation and characterisation of such states will be critical for the development of quantum computers that can tackle real world problems.

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To realize practical quantum computing we need to engineer stable nanostructure with reliable quantum features. It is great to demonstrate the physic concepts, but it requires a lot of engineering to put it into business from concept-to-capability-to-cash. Real practical quantum computing maybe 10 to 20 years away, but FET initiatives today are sensible. If might be that several development on the road to quantum computing probably will help better understand sub 10 (7 or 4 nm) electronics. This proposal is not (only) on the physics research alone (TRL1), but on the engineering towards practical nanostructure with quantum effect (TRL 2-4): demonstrate reliable working devices with full interfacing toward the outside world (from low Kelvin and nano-meters to normal temperature and interface connectors.) In this sense it is a multi-KET (key enabling technology) including advanced material (near zero Kelvin and devices with atomic layer thickness), nano-electronics and nano-technology as well as certain photonic components.
Over the last decades Europe lost the lead in several industries as we were not quick enough to create business with new knowledge. Quantum physics was an European development (Planck, Einstein, Bohr, Dirac, Schrodinger) and we can’t effort to lose the lead here again. The ambition is not so much on societal challenges of the next decade, it is on preparing a competitive position for European industry in a very promising field beyond 2030. Note that the transistor took 20 years before the first chips and another 20 years before the first real useful PCs. Today developments might go faster, but still it will take time as we now need to bridge to gap between concept into a capability to make the first real quantum computers in Europe first.
We started this challenge to create the first real quantum computer in the Qutech cooperation between TUDelft and TNO in Delft, Netherlands. Here the experimental results of the last years of the TUDelft are now put into a more engineering environment in order to accelerate the progress. Nevertheless all available resources within Europe might be needed to keep the progress ahead.

Egbert-Jan Sol, TNO Industry, Radboud University, KET Sherpa member

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Quantum control: A key facilitator for quantum technologies

Quantum control: Definitions and status

It is control that turns scientific knowledge into useful technology: It is used to manage production lines, optimize the flow of traffic, or maintain the temperature in office buildings. Control allows us to maximize efficiency and minimize resource consumption. Originally developed in the 1960s to facilitate engineering work and famously applied to find optimal trajectories to reach the moon by the Apollo missions, optimal control theory has evolved and expanded with the rest of physics – it is presently found in areas as diverse as optical spectroscopy, photochemistry, magnetic resonance and quantum information processing.

The first applications of optimal control theory to the realm of quantum mechanics were reported in the 1980s, dealing with the design of shaped laser and radio-frequency pulses to manipulate chemical reactions and spin systems, respectively. Today, the field of quantum optimal control is part of the effort to engineer quantum technologies from the bottom up: atomic-scale defects in diamonds were recently used as super-sensitive magnetic sensors and a better understanding of photosynthesis was used to improve the design of solar cells. Quantum-enabled technologies will be based on exploiting even more elusive yet very powerful resources – quantum interference and entanglement. Their design will not be possible without quantum optimal control -- quantum optimal control will be crucial to reach the required precision given the sensitivity, power, timing and accuracy of the instruments as well as the ever-present interaction with the environment that may destroy the quantum resources.

Quantum control as an enabler of quantum technologies

Quantum control links the goals set forth by the Commission in computation, metrology, sensing and simulation to hardware platforms in atomic/optical and solid-state physics. It will enable them by identifying how external control knobs must be tuned to allow given hardware with all its imperfections to accomplish the required tasks as good as possible. Such imperfections can be decoherence by coupling to environment, the presence of non-computational degrees of freedom, or imperfections in the external fields themselves. Current tasks include

1.The preparation of nonclassical states that are relevant for metrology and sensing, such as squeezed and N00N states.
2.The realization of quantum gates for quantum computation and digital quantum simulation
3.The tayloring of quantum dynamics towards a desired system in analogue quantum simulation.

Quantum control is also important for quantum communication and information security. First of all, quantum communication networks need small quantum processors as quantum repeaters, the operation of which will benefit from optimal control as stated above. Also, the conversion of photons in quantum communication from the optical range that is most suitable for long-distance links to quantum processors that often operate in the microwave range is a task that can benefit from quantum control. Finally, non-traditional transmission lines for quantum states such as spin chains can be benchmarked once optimized by control.

A paradigmatic challenge when taking quantum physics from a descriptive science to engineering is that engineered quantum systems are necessarily open, i.e., subject to external perturbations aiming at rendering them classical. While in traditional engineering, i.e., of CMOS devices, one aims to stay at the classical side of this boundary, quantum technologies aim at maintaining quantumness as well as possible.

Control of open systems is a current challenge at the frontier of quantum control research. It takes a number of distinct approaches: On the one hand, it stages the battle against decoherence in clarifying what quantum tasks can be accomplished with what precision in the presence of decoherence. As a result, it finds pulse sequences and shapes that often outperform faster sequences in the presence of decoherence. On the other hand, optimal control can also aid in environment engineering, i.e., in utilizing the environment to achieve what would be unattainable in a pure quantum system.

The connection of quantum control within quantum technologies to quantum control more broadly defined helps to advance both. For example, most recently, detection techniques of single-electron spins in nitrogen vacancy centers (NV) of diamonds have boosted magnetic resonance. They carry the potential for dramatic sensitivity enhancement of magnetic resonance spectroscopy as well as imaging in biological and medical applications as well as in material science. This is a typical example of cross-fertilization between the disciplines of quantum physics, sensing and spectroscopy that was triggered by fully exploiting quantum control.

Two new systems have emerged as well-controlled few-body quantum technologies: a) ultracold molecules and reactions related to them and b) novel coherent spectroscopies motivated by new fast light sources. These have become technologically accessible only through quantum control as their complexity cannot be mastered by intuitive approaches.

Answers to key questions

1. What should be the orientation of research on this topic?

We believe that quantum control is essential for substantial advancement towards practical applications of quantum technologies as defined within FET. Our suggestion builds on the established experience that quantum optimal control allows to typically improve the relevant figures of merit by one to two orders of magnitude without requiring any other changes.

Quantum control should therefore become a key area within the current quantum technologies funding. It should focus on quantum control to enable tasks that have already been identified but could not yet be realized with standard approaches. This improvement will make the decisive difference in reaching the next level in the process of taking quantum technologies from proof-of-principle demonstrations to real applications.

2. Have any recent scientific results been obtained relevant to this topic? Is there already a well-established community on this?

Quantum optimal control has been pursued for almost three decades and with rather different objectives in laser chemistry, NMR/EPR, AMO physics, and applied mathematics. Recently, it has started to play a role in quantum technological applications and highlights of European research in this area include:

A.Creation of high-quality entangled spin states in diamond for quantum memories and networks
B.Engineering of Bose-Einstein condensates to advance sensing and metrology at its natural limits
C.Fast calibration of ultraprecise quantum gates on a superconducting qubit platform

Within FP 7, Coordination Action QUAINT has brought part of the researchers from the different backgrounds with their diverse cultures together, in order to build one single community that would be so important for advancing European research in quantum-enabled technologies. Cross-fertilization between them is already visible. However, establishing common terminology and common standards has proven to be a non-trivial task and resulted in establishment of a Virtual Institute for Quantum Control for continuity of the effort and improved outreach.

Taking quantum control visibly onto the agenda of FET programmes would foster the further development of community building by allocating crucial resources to a subject that we believe is vital for the substantive advancement of quantum technologies. Such enhanced visibility would come at a stage where the quantum control community has sufficiently matured to contribute in a profound and substantial way to subjects that are crucial to the further advancement of quantum technologies such as robustness to noise and uncertainty in experiments, adaptation to highercomplexity systems and more powerful operations.

3.Do you know of related initiatives, at national level, or in other continents?

Quantum control has been a major focus for research support recently all across the globe. A good part of this is in direct competition with European efforts, in particular with respect to attracting key brainpower.

Canada is heavily investing in quantum control with a very applied orientation. It has always been a stronghold of laser chemistry and the development of novel spectroscopies. Quite recently, the Canadian Excellence Research Chair (CERC) program has appointed David Cory, formerly of MIT, to the University of Waterloo - Cory is a pioneer and leader of quantum control, most notably in magnetic resonance.

The United States of America fund quantum technologies with an angle on defense and intelligence. Quantum optimal control was stated as a necessary ingredient of the multi-qubit program currently run by the Intelligence Advanced Research Projects Agency (IARPA).

Australia is focusing heavily on quantum technologies. Much of its effort in quantum control is focused on quantum feedback control, but open loop control plays an increasing role. Australia's Centre for Quantum Computation and Communication Technology has a concerted effort on Quantum Control, so has the new Australian Research Council Centre of Excellence for Engineered Quantum Systems. Australia is very aggressive in strategically hiring researchers from other countries including a brain drain from Europe.

In Japan, quantum control is called 'Quantum Cybernetics' and there is a huge program run by the Ministry of Education. This is done concurrently within the large quantum technologies center at RIKEN.

China has recognized Quantum Control as strategic research area for its next programs in research funding.

Switzerland is heavily investing into an over-arching network on Quantum Science and Technology (QSIT) coordinated by ETH Zurich. Its motivation explicitly says that “the exquisite control of quantum systems has become an experimental reality. […] Experimental quantum science has emerged […] to a research endeavor with an enormous technological potential with particular applications in information science and sensors. The multi-disciplinary approach […] connects different systems and […] concepts from physics, chemistry, engineering, and computer science."

There is a variety of national research initiatives involving quantum control in EU member countries. Specifically, the United Kingdom is developing a network of quantum technology hubs and many of the proposed hubs have a significant component of quantum control.

4. What is needed at this point to advance this?

Within the existing EU portofolio of quantum technologies control theorists and practitioners often find themselves embedded into research initiatives driven by applications, i.e., by specific hardware platforms such as superconducting qubits or specific technical goals such as quantum simulation. This is a good start and should be made more firm in future calls for quantum technology projects. It is however not sufficient to take quantum control out of its niche and maximize its impact for all areas of quantum technologies research. We believe that the latter can be achieved by making quantum
control an explicit focus in future FET calls. The corresponding projects would lead e.g. to the identification of the most efficient use of physical resources for quantum technological goals such as implementation of quantum operations or preparation of quantum resources. The notion of efficiency here naturally includes time-efficiency and robustness to decoherence and noise as well as to parameter uncertainty. Such a program could be cross-platform and held together by the quantum control techniques being used. In fact, we have seen over the last years how important it is that quantum control researchers motivated by very different physical systems work together and jointly advance their techniques.

Finally, we believe that the tasks that had been identified as crucial for quantum technologies in the past, such as those listed under 1-3 above, should be amended by two subjects -- ultracold chemistry and spectroscopy with novel light sources. These two fields have seen substantial progress over the last few years such that they are now at the stage of becoming technologically relevant. They share with the physical systems investigated under the quantum technologies umbrella so far that a few degrees of freedom are sufficiently well isolated and behave fully quantum mechanically -- just as the trapped ions or photons, the work on which has been awarded the Nobel prize in 2012. Adding these subjects to the quantum technologies portfolio would thus be natural and allow for cross-fertilization with the subjects already established in quantum technologies research.

Virtual Institute of Quantum Control, founded by the EC Coordination Action on Optimal Control of Quantum Systems (QUAINT), https://quantumcontrol.eu/
Executive secretary:
Dr. Frank Wilhelm-Mauch, Professor of Physics, Saarland University, Germany

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Going beyond the merits of individual subfields, I find comments like "QT-Flagship for European competitiveness" and "Bring Qu-computing as a KET from TRL1 to TRL2-4" particularly pertinent and would second their main message. Regarding the comparison with the US, I would like to add a few points that underline the urgency of a broader effort if Europe wants to stay competitive.
Quantum computing research is not only moving to venture capital companies like D-Wave, but increasingly to more secretive organizations such as defense contractors and government labs. There are programs on superconducting qubits at Northrop Grumman and Lincoln Labs about which little is known, and HRL has revealing little about their work on SiGe quantum dot spin qubits since their breakthrough paper in 2012 (doi:10.1038/nature10707). The NSA is reported to issue guidelines for when they would like quantum computing research to be classified, and key criteria are only a factor four away from currently published results. Recent events show that it is not entirely beyond reason for Europe to strive to remain competitive.

Comparing US and European funding opportunities, I find that instruments to support large programs at a single of few institutions are missing in the EU. Examples in the US include activities at IBM Research, Yale, UCSB and HRL, representing concerted efforts of on the order of 20 or more researchers each. Some of these are actively hiring the top PhDs in the field. There are few ways in which European groups could maintain such large scale activities. As far as I can tell, most funding instruments tend to spread efforts over a rather large number of groups each receiving sub-critical resources (e.g. 1-2 researcher positions). Established ERC grants are better, but still too small in scale. Synergy grants certainly would create exciting opportunities.

It is also useful to look at the evaluation criteria of ERC grants. The focus on potential breakthroughs makes me wonder if the kind of long term, thorough and difficult engineering required to make truly technological advances in many areas of quantum science and engineering (universal quantum processors, repeaters) would be rated highly. Scientific breakthroughs and the exploration of new avenues are needed, but at the same time I believe that it is time to push the systematic development of the most successful approaches. Given that it is in principle quite clear what needs to be done, but achieving progress requires a tedious amount of details and complexity to be addressed, I am not sure that a technology-oriented QC proposal would do very well in an ERC competition. Another point to consider is that the kind of engineering work needed (automatic tuning, scalable control hardware, wiring, material properties, fabrication yield etc.) will not lead to many publications in high profile journals, which may reduce the attractiveness for researchers. This is not to imply that existing funding experiments and collaborative, distributed efforts are useless, but I believe they do not cover all needs. My (perhaps somewhat bold) suggestion would be to ramp up grants similar to ERC-Synergy, but with a clear focus on quantum technology engineering. A challenge will be to leave enough freedom to researchers while still maintaining them on a technology-oriented track.
Of course, such a development should not lead to other, smaller groups being left without funding, as these are still needed to drive more exploratory innovation and to educate a quantum technology work force.

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Photons are an ideal tool for qu-bit encoding and integrated photonic circuits can give a real boost to the application of quantum technologies.
Integrated photonic circuits are also an ideal platform for the simulation of quantum processes and can help to understand underlying mechanisms

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Quantum technology, which exploits the properties of entanglement and squeezing, has been applied in recent years to the fields of “secure communication” and “metrology and sensing”. For over three years now, squeezed light has been used to improve the measurement sensitivity of the gravitational-wave detector GEO600 beyond classical limitations. Although “quantum technology” is already a reality in these fields, its potential is far from being fully realised. It allows for arbitrarily secure communication, regardless of future eavesdropping technology, and arbitrarily sensitive measurements, regardless of the effect of measurement back-action noise.
Further research and development is required on optical technologies including low loss optical fibres, low loss optical mirror coatings, as well as quantum-noise limited laser light sources, e.g. light sources for single photons, as well as squeezed and entangled light.
Europe needs targeted funding for research and development, as well as networking to make new quantum technologies a reality and to improve existing quantum technologies to exploit their potential on a grand scale.
Roman Schnabel, Leibniz University Hannover

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Quantum technologies offer the possibility to enhance the performance of existing systems in addition to generating new sensing and imaging techniques beyond those available in classical devices. The future emerging technologies that will be enabled by studying Quantum Technologies and the Interaction of Light and Matter offer the potential of transformative new technologies in the global challenge areas of security, healthcare and environmental monitoring.
Several ultra-sensitive displacement sensors, based on interferometric measurement, are/will dominated by quantum noise across the majority of their operating bandwidth (GEO-HF: http://www.geo600.org/1037150/GEO_High_ Frequency, Advanced VIRGO: https://wwwcascina.virgo.infn.it/advirgo/). Quantum noise occurs both at the large scale, such as in these long baseline gravitational wave detectors, and also at the millimeter scale, such as table top prototypes and cavity opto-mechanical experiments (http://www.cqom-itn.net/). Quantum technologies, based on squeezed states of light, promises the reduction of the quantum noise in a wide frequency range (both in shot noise and radiation pressure) by up to an order of magnitude. To achieve this target requires a series of developments in the area of optical technologies including low loss optical mirror coatings, new dielectric sputtered/epitaxially grown optical coatings and structured coating free mirrors, novel control techniques with high optical powers (optical springs) and the development ultra low noise, high stability, optical reference cavities.
There are strong links to established international collaborations within these areas including the International Max-Planck partnership (http://www.epsnews.eu/2014/ 01/first-impp-by-scots/), and Optical Frequency and Metrology standards (http://www.mpq.mpg.de/~haensch/comb/). There further exists high potential for cross field collaboration, where techniques can be further applied to future emerging technologies including;

• squeezed light sources for biological imaging
• imaging beyond line of sight with entangled systems
• aberration free imaging
• monitoring of temporal gravitational fields and single photon detectors with the visible-IR bandwidth.
• high damage threshold coatings for laser mirrors
• narrow band optical filters for fluorescence microscopy
• development of high sensitivity accelerometers based on both atom interferometry or classical MEMS, which are readout with sub-shot noise interferometric readouts
• highly specific gas sensors and compact Raman spectrometers.

There is significant potential for novel sensing at and beyond the standard quantum limit which can be enabled through the expertise that exists across various institutions and companies within Europe.

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It is clear that in most of the blogs contained here, the keywords

quantum transport in electronic circuits
quantum coherence
mesoscopic phenomena
novel materials / hybrid systems

appear in explicit or implicit form. Topological insulators ( e.g. BiSe or BiTe) and semiconductor/ superconductor hybrid devices ( including HTc materials ) and LAOSTO offer a mature playground for spintronics, spin valves, qubit enegeneering, down to thermoelectric devices and witness presently a burst of activity that should be immediately fostered by the FET Work Programme. Boundary states of Dirac electron materials and, possibly, Majorana Fermions are the perfect tool for quantum coherent transport and for exciting developements in Quantum Technology.

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Quantum technologies involve the control and manipulation of quantum systems to achieve results not possible with classical matter. Naively, they can be seen just as the next step on from nanotechnology while still following traditional paradigms. However, quantum technologies give much more than this as they transfer technological applications to a different physical framework where devices are described by quantum laws. All technologies derive their power and their limitations from the laws of physics. Thus, bringing technology to a new and broader physical framework can provide fundamentally new capabilities. And in fact, these quantum technologies offer much more than cramming more and more bits to silicon and multiplying the clock–speed of the ubiquitous microprocessors: they support entirely new modes of computation with qualitatively new and powerful algorithms based on quantum principles, that do not have any classical analogues; they also offer provably secure communications, simulation capabilities unattainable with classical processors and sensors and clocks with unprecedented sensitivity and accuracy.
The present document provides an overview on the main advances in the last years in quantum technologies and identifies game-changing directions for future research. Moreover, it discusses how all this research effort can be incorporated within future proactive initiatives to be included in the next FET work programme for 2016 and 2017.
Since many years, quantum technologies have experienced impressive progress and gained a clear European dimension. This has been realized by many national agencies, both in Europe and worldwide. For example, a strong quantum repeater project has recently been launched in the US. Another important on-going effort includes the recent UK investment of £270M. Yet, a comprehensive European synergy is essential for the full development of the field. From a scientific point of view, a comparably high level of synergy needs to be maintained between the fundamental and the application-oriented side of quantum technology research, according to the approach that FET has followed in this field since its inception.
The framework for interaction and coordination with the scientific branches of the EU research community in quantum technologies is structured around a set of five Virtual Institutes (VIs): the Virtual Institute of Quantum Communication, the Virtual Institute of Quantum Computation, the Virtual Institute of Quantum Information Sciences, the Virtual Institute of Quantum Simulation and the Virtual Institute of Quantum Metrology, Sensing, and Imaging. Each VI unites some prominent experts in the corresponding field, providing a contact point for consultation and feedback in the relevant areas. The different VIs have partially overlapping research agendas to facilitate close collaborations, complementing rather than duplicating each other. Following the development of the field, new VIs could be established in the future. Under consideration are for example a VI of Quantum Engineering (a topic that receives increased attention on the road to extended quantum circuits) and one of Quantum Control (a system of concepts and methods underlying the implementation of quantum devices). This document is structured around the areas of the currently existing five Vis and has been prepared in collaboration with the Directors and Executive Secretaries of all the VIs. For each of the areas, it describes the main objectives, the state of the art and the future challenges.

Quantum Communication

Objectives: Quantum communication is the art of transferring a quantum state from one location to another; in this way information, or resources such as entanglement, can be distributed among different locations. From an application point of view, a major interest has been focused on Quantum Key Distribution (QKD), as this offers a provably secure way to establish a confidential key between distributed partners. This has the potential to solve long-standing and central security issues in our information based society as well as emerging problems associated with long term secure storage (e.g. for health records and infrastructure) and will be critical for the secure operation of applications involving the Internet of Things (IoT) and cloud networking.
State of the art: In the last years the field has seen enormous progress, as QKD systems have gone from table-top experiments to compact and autonomous systems and now a growing commercial market. More generally there has been an explosion in the number of groups active in the field working on increasingly diverse physical systems. Quantum memories and interfaces have moved from theory to a wide range of proof-of-principle demonstrations with encouraging results for the future. Conceptually, the idea of device independent quantum information processing made its appearance and has already started to find experimentally feasible applications. While the realisation of basic quantum communication technologies is becoming more routine in the laboratory, non-trivial problems emerge in high-bit-rate systems and long-distance applications as we interface the different technologies and as the network complexity increases.
Future directions: One of the emerging areas of interest for quantum communication schemes is in connecting the nodes within quantum simulators, which can either be all located in the one lab, or more interestingly, in distributed scenarios - the tools from quantum communication playing the role of wiring circuits for these quantum computers. A particular application is a network of entangled clocks providing precise and secure world time reference. While there remain many challenges for proof-of-principle laboratory demonstrations, the transition to deployment in real-world environments defines a new set of challenges in the quantum information domain. The issues of scale, range, reliability, and robustness that are critical in this transition cannot be resolved by incremental improvements, but rather need to be addressed by making them the focal point of the research and technology development agenda as we work towards a quantum internet. To succeed, this needs to target the underlying technologies, ranging from fundamental aspects of engineering quantum systems to integrating quantum and classical, e.g. fast (classical) opto-electrical systems, as well as the end-user applications themselves. In particular the following need to be addressed:
• Quantum networks, beyond point-to-point, exploring novel protocols, possibly hybrid (continuous-variable and discrete) systems. Quantum repeater concepts will also be critical in the context of computation and simulation, both for short distance scales (local) or large (distributed) processing systems.
• Deterministic and scalable technologies involving on-demand photonic sources, or heralded sources with quantum memories, including quantum memories with multimode capacity.
• Interfaces allowing for the coherent transduction of quantum states between different physical systems.
• The synchronisation and stabilisation of distributed quantum systems and their characterisation – in particular, their quantification with local measurements.
• Device-independent quantum information processing needs to be further investigated and ways to move from purely theoretical concepts to more practical scenarios will be highly relevant. In particular, addressing both QKD and quantum random number generation and providing a new perspective with the potential to also minimise security assumptions and hence simplify the security of real-world quantum communication.
• Systems that exploit increased complexity, e.g. using integrated quantum photonics, which would allow new functionality and protocols in quantum networking. 

Quantum Computation

Objectives: A quantum computer is a device that harnesses some of the basic laws of quantum mechanics in order to solve problems in more efficient ways than classical (standard) computers. The main objective in the field of quantum computation is to build such a device. Other objectives include the development of quantum algorithms to solve specific problems, and the creation of interfaces between quantum computers and communication systems. The construction of a quantum computer with thousands of quantum bits would have tremendous consequences on the security in communications (like the internet), by breaking most of everyday used cryptography. It would also allow us to solve certain problems that the most powerful super computers are not able to solve now or in the near future, and possibly never; in particular, those dealing with quantum many-body systems, as they appear in different fields of physics, chemistry, and material science.
State of the art: We already know that the basic principles of quantum computation are correct and there is no fundamental obstacle in constructing such a powerful machine. The basic building blocks of a quantum computer have been demonstrated with many different technologies, including trapped ions, neutral atoms, photons, NV-centers in diamonds, quantum dots, and superconducting devices. Small prototypes have been built using some of those technologies, and some of the quantum algorithms have been demonstrated. The most advanced technologies at the moment are trapped ions and superconducting qubits. With the first one, coherent control has been achieved with up to 15 qubits. Although the control of the latter is still not at the level of the first, it has the potentiality of being scaled up much more easily. With both technologies, proof-of-principle experiments on quantum error correction have been carried out.
Future directions: Despite the strong efforts devoted by many scientists during the last years, the objective of building a quantum computer remains as a central challenge in science. The main obstacle to build a quantum computer is the presence of decoherence, i.e., undesired interactions between the computer’s constituents and the environment. Standard isolation is not a valid solution, since it seems impossible to reach the levels of isolation that are required in large computations. Therefore, the construction of such a device will require the use of quantum error correction techniques. It is not clear, however, which (already or not yet existing) technology will be optimally suited for the implementation of such techniques in a scalable way and/or in distributed settings. On a different note, we only know a limited class of problems where a quantum computer could overcome the limitations of classical ones, and thus theoretical studies for applications of such devices need to be further pursued.
Some specific future directions of research include:
• Further development of all current technologies to understand their limitations and find ways around them.
• Assessment of the capabilities of different technologies for being scaled up.
• Optimization of the performance of error correcting codes, by both increasing the error threshold and decreasing the overhead of required qubits.
• Investigation of new ways of performing quantum computation, in particular based on self-correcting codes (as they appear in topological systems).
• Development of new quantum algorithms and search for problems where quantum computers will be required.
• Development of quantum complexity theory and its application to many body physics.
• Building interfaces between quantum computers and communication systems.
• Development of quantum-proof cryptography to achieve forward-in-time security against possible future decryption (by quantum computers) of encrypted stored data.
• Development of quantum undecidability theory.

Quantum Information Sciences

Objectives: The development of quantum technologies has been driven by theoretical work of scientists working on the boundary between Physics, Computer Science, Mathematics, and Information Theory. In the early stages of this development, theoretical work has often been far ahead of experimental realization of these ideas. At the same time, theory has provided a number of proposals of how to implement basic ideas and concepts from quantum information in specific physical systems. These ideas are now forming the basis for successful experimental work in the laboratory, driving forward the development of tools that will in turn form the basis for all future technologies which employ, control and manipulate matter and radiation at the quantum level.
State of the art: in recent years, novel theoretical ideas have been proposed, extending the range of applicability of quantum information protocols. The novel scenario of device-independent quantum information processing has emerged, where protocols are defined independently of the inner working of the devices used in the implementation. This new approach has led to self-certified schemes for QKD and randomness generation. A strong theoretical effort has opened quantum simulation to quantum field theories and quantum chemistry. From a purely information theory point of view, non-additivity effects of channel capacities with no classical analogue have been proven. Finally, quantum information theory has established strong bridges with other fields, such as condensed matter, quantum thermodynamics, biology or quantum gravity. The study of topological systems for quantum information purposes, the development of novel numerical methods for the classical simulation of many-body quantum systems, the study of Hamiltonian complexity or, more recently, the use of quantum information techniques for a better understanding of the physics of black holes, as well as applications in mathematics and computer science, are examples of these synergies.
Future directions: the impressive experimental progress in controlling quantum particles has brought the field to a regime where experimental setups can hardly be simulated in existing classical computing devices. The design of methods to estimate, control and certify these complex setups is essential for the development of the field. Also, we expect quantum information theory to extend and strengthen its applicability to other fields, providing new insights in quantum thermodynamics, many-body physics or quantum gravity. The recent device-independent scenario, in which protocols are defined independently of the inner working of the devices, also offers promising perspectives, especially for cryptographic applications.
Relevant research directions for the next years include:
• Methods for the reconstruction and estimation of complex quantum states or channels beyond tomography protocols, which are as hard as simulating a quantum system classically.
• Methods for the certification and validation of quantum processes; benchmarking of purely quantum effects with no classical analogue.
• Methods for error correction beyond quantum computation and study of their application to quantum simulation, communication or sensing.
• Methods for the control of complex quantum setups
• Development of device-independent solutions: novel protocols, general framework for security analysis in this approach or feasible proposals for their experimental realization.
• Novel applications of quantum information concepts in other fields, such as thermodynamics, many-body systems, mathematics, computer science, biology, quantum chemistry, high-energy physics or quantum gravity.

Quantum Simulation

Objectives: Quantum simulation uses controllable quantum systems to investigate the properties of other complex quantum systems, and can tackle problems that are beyond the computational capability of any classical computer. Initial experimental and theoretical work has been mainly directed towards the quantum simulation of condensed matter systems, such as bosonic or fermionic particles in lattices, but more recent work also encompasses such diverse fields as quantum field theory, cosmology and high-energy physics.
State of the art: Experimental platforms for quantum simulation comprise ultracold atomic and molecular quantum gases, ion traps, polariton condensates, circuit-based cavity quantum electrodynamics and arrays of quantum dots or Josephson junctions. All of these platforms aim to explore the potential of quantum simulations for different fields of science. The first demonstrations of quantum simulation were performed on ultra-cold atoms. In this platform, the quantum-gas microscope technique has opened up novel possibilities to probe and manipulate cold-atom quantum simulators at the single-particle level. For trapped ions, the extraordinary level of control of motional and internal quantum states has enabled for example the realization of a digital quantum simulator, and analogue quantum simulation of different spin systems. Recently, also solid-state systems like coupled arrays of cavities or superconducting qubit arrays, or arrays of defect centres, are being explored for quantum simulation purposes.
Future directions: The challenges of the science of quantum simulation can be divided into four categories that need to be addressed:
• Novel manipulation and detection schemes for quantum many-body systems to further improve the controllability of artificial quantum matter realized for quantum simulation purposes. This includes improving fidelities of present preparation schemes, as well a devising novel measurement and control techniques and also include identifying completely novel systems for quantum simulations.
• Extend the reach of quantum simulations into other fields of science, e.g. quantum field theories in high-energy physics, nuclear physics, cosmology (simulation of non-equilibrium dynamics), biology, chemistry and material science.
• Novel strategies toward lower temperatures and entropies of many-body systems. This will allow exploring novel quantum phases of matter that could find important impact in metrology (e.g. atomic clocks), quantum computing or material science.
• Novel strategies for the verification of quantum simulations, studying how finite temperature errors and imperfections in implementations of couplings affect the resulting many-body state.

Quantum Metrology, Sensing, and Imaging

Objectives: Specifically quantum phenomena such as coherence and entanglement can be exploited to develop new modes of measurements, sensing, and imaging that offer unprecedented levels of precision, spatial and temporal resolution, and possibly auto-compensation against certain environmental factors, such as dispersion. These promising applications require development of techniques that will be robust against noise and imperfections to be deployed in real-world scenarios. Quantum technologies will benefit in particular time and frequency standards, light-based calibration, gravitometry, magnetometry, accelerometry, including the prospects of offering new medical diagnostic tools.
State of the art: Reaching quantum-enhanced precision beyond standard quantum limits in metrology relies on generating non-classical collective states of atoms and non-classical multi-photon states of light. Extensive effort has been dedicated to these goals with proof-of-principle demonstrations in the atomic domain and the first squeezed-light-enhanced operation of a gravitational wave detector with practical suppression of vacuum fluctuations. Novel concepts, such as systems with an effective negative mass or negative frequency have been shown to be capable of providing magnetometry with virtually unlimited sensitivity. Possibilities to define new frequency standards have been explored with the readout based on quantum logic techniques borrowed directly from the field of quantum computing and with entangled atoms providing ultimate quantum sensitivity. Enormous progress has been made on single photon sources, both deterministic and heralded, that can be used for optical calibration as well as a building block for photonic quantum communication and computing. Artificial atoms (such as nitrogen vacancy centers) have been investigated as ultraprecise sensors e.g. in magnetometry.
Future directions: Original techniques are needed to make quantum-enhanced metrology and sensing deployable in non-laboratory environments. Because of the wide range of prospective applications and their specificity, a broad range of physical platforms needs to be considered, including (but not limited to) trapped ions, ultra-cold atoms and room-temperature atomic vapours, artificial systems such as quantum dots and defect centers, as well as all-optical set-ups based e.g. on nonlinear optical interactions. Thorough theoretical analysis of noise mechanisms is needed, leading to feasible proposals that will be subsequently implemented to realize quantum-enhanced strategies.
In particular the following need to be addressed:
• Novel sources of non-classical radiation and methods to engineer quantum states of matter are required to attain quantum-enhanced operation.
• Develop detection schemes that are optimized with respect to extracting relevant information from physical systems, with optimization criteria selected for specific applications. These techniques may find applications in other photonic technologies, e.g. increasing transmission rates in optical communication.
• Micro- and nanofabrication of quantum sensors including integration with fiber networks
• Development of hybrid quantum sensors that use optimal quantum interfaces for transduction of signals across the electro-magnetic radiation spectrum.
• Compact solutions for quantum imaging, allowing for the interconversion of detected frequencies including preservation of coherence, as well as quantum ranging and timing that can suppress the spatial/temporal spread of transmitted signals.
• Implementation of entanglement assisted atom clocks.
• Study of the performance of quantum sensing protocols in realistic regimes including noise and losses.
• Extend the reach of quantum sensing and metrology into other fields of science to uncover novel natural phenomena, e.g. biology, fundamental physics, high-energy physics, quantum gravity. 

Global perspective and role in the work programme

While the previous presentation has been structured along the different VI’s, the field of quantum technologies has to proceed as a coherent and unified research effort. Indeed, many synergies among the different research directions are expected and essential to attain the previous objectives. To name just a couple of illustrative examples, detection and state-preparation techniques developed in the context of quantum communication will find an application in sensing scenarios, and error-correction techniques developed in the context of quantum computation will be needed for the certification of quantum simulations. In this sense, the role of basic science and theoretical new ideas is essential, as new disruptive theoretical proposals can significantly boost many of the previous promising applications of quantum technologies. Progress in all of these areas is reliant on fundamental research to improve and find new enabling technologies and concepts.
Quantum technologies are already present in the current work programme. Recently, there has been a proactive call on quantum simulation. There are also explicit mentions to quantum concepts in the work programme: in ICT 25 - 2015: Generic micro- and nano-electronic technologies, projects may include activities “related to modelling and simulation: e.g. quantum and atomic scale effects” or study “new computing paradigms like quantum computing”; in ICT 26 - 2014: Photonics KET, new device concepts “based on quantum optics or quantum technologies” are mentioned in the context of disruptive sensing technologies; finally, in ICT 32-2014: Cybersecurity, Trustworthy ICT, post-quantum key distribution and several aspects of QKD appear.
In our vision, the framework programme for the next years is a key funding mechanism to support and unite all the previous research activities, from basic theoretical research to industrial applications. In this sense, we expect quantum technologies to gain an even more visible role in future research funding in Europe. A proactive call on quantum technologies, complementary to the recent one on quantum simulations, is timely and can help in bringing the developments described above much closer to applications. As mentioned, theoretical ideas should remain visible in the programme, as we are still far from understanding all that quantum properties can offer for technological purposes. In this context, the emerging field of quantum engineering, with its novel possibilities to create devices that can prove scientific principles, offers an exciting new addition to a proactive call. Finally, we also expect quantum aspects to increase their relevance in the photonics, security and nano-technologies programs. For instance, the possibility of self-certified protocols using device-independent techniques brings cryptographic applications to a significantly stronger level of security where a much lower level of trust is needed on the provider. Also, new photonic devices operating at the quantum scale will emerge from the research effort in photonics and nano-technologies. In this sense, calls in these programs parallel to those in FET can be expected to deliver a major synergy effect.
Let us conclude by mentioning that bridging the gap between blue-sky research and applications will take time and several iterations. It should also be understood at this early stage of researching quantum technologies that in all likelihood there will not be one single solution, but many, on the way to developing this key enabling technology of the 21st century and to build a quantum industry.

This memorandum is endorsed by
Antonio Acin (QUTE-EUROPE VI Coordinator), Tommaso Calarco (QUTE-EUROPE Roadmap coordinator), Daniele Binosi (QUTE-EUROPE Executive Secretary), Nicolas Gisin (Director, VI of Quantum Communication), Rob Thew (Executive Secretary, VI of Quantum Communication), Juan-Ignacio Cirac (Director, VI of Quantum Computation), M. Wolf (Executive Secretary, VI of Quantum Computation), Peter Zoller (Director, VI of Quantum Information Science), Immanuel Bloch (Director, VI of Quantum Simulation), Stefan Kuhr (Executive Secretary, VI of Quantum Simulation), Ian Walmsley (Director, VI of Quantum Metrology, Sensing, and Imaging), Konrad Banaszek (Executive Secretary, VI of Quantum Metrology, Sensing, and Imaging); Alain Aspect, Rainer Blatt, Harry Buhrman, Nicolas Cerf, Artur Ekert, Atac Imamoglu, Massimo Inguscio, Sir Peter Knight, Leo Kouwenhoven, Maciej Lewenstein, Martin Plenio, Eugene Polzik, Gerhard Rempe, Reinhard Werner, Anton Zeilinger.

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Quantum technologies as a single proactive topic is, in my opinion, a very broad topic. There are several high-level scientific communities working of various experimental platforms (optic, electron spins, ultracold atoms, ions, Josephson devices, etc.) that can deliver valuable results. The amount of funding for this topic should take into consideration the size of these communities as well as the very high level of interest that it generates, both amongst the experts and the general public.

One technology where there has been considerable amount of progress in the last years is that of superconducting coherent circuits - electrical circuits realized as a combination of Josephson-based devices (realizing qubits) and coplanar waveguide resonators. The basic components exist, the physics behind them is reasonably well understood, and the fabrication process is reproducible. It is one of the best experimental platforms for implementing quantum technologies. As mentioned already here by some contributors (whose view I support and I will echo below), there are several directions that look extremely promising:
1) simulations of models from field theory and from many-body physics on a superconducting platform; simulations of molecules with relevance for biology (e.g. proteins) and material sciences.
2) solving the issue of "quantumness" in the D-wave (or similar) circuit. An European flagship would be a good initiative.
3) amplifiers with quantum-limited added noise, parametric effects and creation of microwave squeezed states,
4) hybrid technologies centered around superconducting circuits. Combining other materials and devices (nanomechanical resonators, NV centers, etc.) that can be addressed for example optically and are coupled with qubits and resonators.
5) exploring unconventional ideas as well as fundamental physics on a superconducting-circuit platform (for example probabilistic amplifiers, weak measurements, etc.)

Sorin Paraoanu,
Aalto University, Finland

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There has been a strong focus in quantum technology on computing and information processing applications. While these are interesting applications, there are other areas where quantum technology could have a significant impact. A particular area of interest is medicial imaging and theranostics. Technologies such as magnetic resonance imaging and spectroscopy (MRI) already exploit quantum effects (nuclear magnetic resonance) to generate images of tissue and identifiy diagnostic biomarkers in-vivo. However, while the technology is quite advanced, this is an area where novel tools such as coherent and incoherent control of quantum dynamics could be deployed to enhance existing diagnostic modalities and create new applications in areas such as tissue characterization, relaxation-optimized ultra-low SAR pulses, detection of chemicial biomarkers by chemically selective pulses, rapid quantitification of biomarkers, etc. Quantum control could be also be applied to exploit quantum properties of functionalized nano-particles to enhance their use as contrast agents in imaging or their therapeutic properties.

S Schirmer
Associate Professor in Physics, College of Science, Swansea University

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On-demand single particle transfer between distant quantum dots combined with quantum gates based on particle-particle interactions provides a pathway for the realization of scalable quantum systems. It has recently been shown that moving quantum dots created by surface acoustic waves (SAWs) can transfer single electrons as well as exciton ensembles on-demand with very high fidelity between remote locations in a semiconductor quantum well separated by several micrometers. Combined with the recent demonstration of single exciton confinement, these results open exciting possibilities for quantum electron-optics in solid-state systems. These systems provide a common platform for quantum interaction of photonic, vibrational, and electronic excitations based on single electrons and single excitons flying along quantum transport channels provided by SAW moving potentials. The motivation for using flying excitations (such as spin-polarized electrons and excitons) lies on the fact that they can be easily inter-conversion to photons, thus allowing optical probing and providing a natural interface between electronic and photonic excitation. The implementation of these quantum interaction schemes require the investigation of the storage and transport of single particles by SAWs, as well as of the interaction between single flying particles during motion. The latter can be realized via the particle-particle interactions based on the coherent tunneling between adjacent quantum channels for single flying electrons as well as flying excitons. These studies will provide the necessary ingredients for the future implementation of a scalable technology for quantum computation.

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Connecting quantum science with scientific challenges of other disciplines such as computer science and electrical engineering is one of the next big leaps towards quantum technology. For quantum computers, we need to go from a handful of “quantum bits” with external control hardware to an intricate circuit with dozens or hundreds of quantum bits on a chip, integrated with classical control and measurement electronics. For quantum communication, the key transition is from point-to-point secure links over a few tens of km, to a true quantum internet with a network of quantum repeater stations. This presents a formidable scientific and technological challenge.
This challenge is not going to be overcome by physicists alone. In the coming years, the effort and expertise of both professional and academic circuit designers, computer architects, process engineers, software engineers, computer scientists etc. will increasingly be needed to complement the physics. Much of the work requires a different mentality, very focused and goal driven, to complement the curiosity driven physics approach. Finally, the funding level required to propel the field into this new phase of building quantum hardware is of a different order of magnitude, rising quickly from millions of euros in past years to tens of millions now and hundreds of millions in several years.

Examples of topics of interest:

- quantum-classical electronic interface. For quantum feedback in a circuit of qubits one needs nearby and fully integrated classical (low-dissipitive!) electronics. The data exchange between qubits and the classical logic needs to be redesigned from scratch in order to obtain a proper quantum interface. In a broader perspective this interface mimics the quantum – classical border from Zurek, but in this case (nearly) all channels from quantum to classical are designed and engineered.

- quantum materials. The materials science giving us topological insulators and quantum spin Hall effects is a very interesting science by itself and it is to a large extent motivated by the realization of topological protected qubits. Buzzwords like (fractionalized) anyons, non-Abelians, Majoranas, non-local storage are always directly connected to a physical materials system, since these are all emerging phenomena in condensed matter.

- quantum device fabrication. From qubits to circuits requires a completely new mindset for fabrication, one that goes beyond the mindset of a physicist. To realize a circuit with ~50 operating elements each building block must be reliable and reproducible to an incredible level. We find it important to welcome electrical engineers into our field. We physicists need them for making the step to quantum circuits

Lieven Vandersypen and Leo Kouwenhoven
on behalf of QuTech / TU Delft

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Keywords: first-principles simulations, computational materials science, materials genome, new states of matter

• What does this topic address?

The goal of this topic is to radically transform and accelerate invention and discovery in science and technology, and especially to transform and accelerate the design and discovery of novel materials, their properties, and their performance in devices in order to rapidly address major and urgent societal issues in the fields of information-and-communication technology, energy, environment protection and health care, and to engineer new states of matter and enable the emergence of novel original physical properties to advance fundamental and applied sciences.

• What is the state-of-the-art and what are the main scientific and technological challenges and opportunities for frontier research that need to be tackled in the next 5-10 years in this area?

Quantum-physical simulations of materials have entered a revolutionary phase, with an exponential explosion in their relevance and technological impact – clearly testified by world-class bibliometric measures (see http://theossrv1.epfl.ch/uploads/Main/Links/APS_Most_Cited_Feb_2013.pdf).

This field is ready for transition to a novel mode for invention and discovery, where accurate, predictive, validated, and inter-operable quantum engines are put in the hands of a computer-science infrastructure that uses a novel generation of tools (massive heterogeneous databases, structure predictors, data mining and machine learning, and high-throughput calculations) to discover or optimize materials and properties.

In the US, the White House announced in June 2011 a “Materials Genome Initiative for Global Competitiveness”, a “new, multi-stakeholder effort to develop an infrastructure to accelerate advanced materials discovery and deployment in the United States” with a “vision of how the development of advanced materials can be accelerated through advances in computational techniques, more effective use of standards, and enhanced data management”.

At the same time, it is Europe that has been leading the effort in first-principles quantum-mechanical simulations, and the entire materials genome field would not be possible without the knowledge and expertise that are present here. We want to make sure that Europe not only maintains and enhances this intellectual leadership, but firmly drives all possible technology transfer and industrial applications.

• Which disciplines are involved?

Physics, chemistry, materials science, biosciences, computer science

• What would be the critical mass of European researchers needed to carry out research in this area? What is the current situation?

Europe has organized itself for more than 20 years in an organization (Psi-k Network, see http://www.psi-k.org ) coordinating the effort of thousands of researchers in the field, and possesses the critical mass and outstanding intellectual capital (but not the resources, and alignment to a vision for innovation) to lead it.

• How is this topic related to recent breakthroughs?

First-principles simulations have reached predictive accuracy in the last few years, often comparable or sometimes even superior to that of experiments, and are ready to be used to engineer or screen materials for target properties and performance. Also, sheer computational power has been on a steady trend where it doubles every 14 months; this is compounded by a simultaneous improvement of the algorithms and the codes used in quantum simulations, and the current computational power at the peta- and exaflop scale allows for systematic screening of hundreds of thousands of materials at a time.

At the same time, the field of “big data” has arisen, and its tools - from machine learning to data mining and data analytics – provide new avenues to rapidly explore massive amount of calculations, and support the entire field of computational science with a materials informatics platform to execute, store, and data mine massive high-throughput searches.

• Why is this research needed now (or when would it be needed)?

The urgency of solving societal problems – from energy to environment to health care – is ever more pressing, and we stand to greatly accelerate this process of invention and discovery by predictive, realistic, massively-parallel, database-driven and database-searching high-throughput simulations, at a time where solutions obtained through the traditional scientific pipeline might not arrive fast enough.

• Why is this topic important?

This is a change of paradigm in invention and discovery, where the accuracy of predictive simulations allows to

- develop novel materials to harvest, store, and convert energy
- solve key technological problems in the roadmap for information and communication technologies
- identify novel materials for health-care applications, and address stability and polymorphism in pharmaceuticals
- maintain the EU leading role in the field of quantum-mechanical simulations, and leverage this vast, world-leading community to the goals of technology transfer and innovation

Prof Risto Nieminen – Aalto University, and Psi-k Chairman
Prof Nicola Marzari – EPFL, Psi-k Trustee
Prof Angel Rubio – Universidad del País Vasco, Psi-k Trustee
Prof Matthias Scheffler – Max Planck Society, Psi-k Trustee

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DE TOUZALIN Aymard European Commission Future and Emerging Technology Unit Deputy Head of Unit
VAN DE VELDE Walter European Commission Future and Emerging Technologies Scientific Officer and FET Strategy
MARQUEZ-GARRIDO Beatrice European Commission Future & Emerging Technologies Unit Project Officer
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