The mechanical phenomenon of entanglement, or "spooky action at a distance", as Einstein put it in 1935, has been proven to be real. Not only for atom-size objects, but for objects that are almost large enough to be visible to the naked eye: this possibility was unthinkable until now. This discovery was made by the HOT project based in Finland, supported by the European Union's Future and Emerging Technologies (FET) programme.

Image of drumheads prepared on silicon chips used in the experiment

This is a wonderful example of how truly exploratory research can yield useful results and, eventually, products that can be used in the real world.

The theory of quantum entanglement described by Einstein says that two objects can affect each other across distances without any direct interaction. No wonder Einstein himself was uncomfortable with this very theory; the phenomenon goes against both classical physics and our basic understanding of reality.

Despite Einstein's discomfort, the 'impossible' is now true. The international team of researchers of the HOT project, funded by the EU's Future and Emerging Technologies (FET) programme, carried out an experiment proving the theory of entanglement applies even to objects that are bigger than microscopic, such as a drumhead the width of a thin human hair nearly visible to the naked eye. In this experiment, two drumheads were made to vibrate at a high ultrasound frequency. The vibrations created the 'spooky' quantum entanglement state for up to half an hour.

The quantum entangled state that the team managed to create is extremely fragile and disappears if the entangled objects are affected by events in their surroundings, such as disturbances in temperature. That is why the experiment required the elimination of all forms of external physical noise. To achieve that, the drumheads were made to interact via a superconducting microwave circuit. The advantage of using the device is that the electromagnetic fields in the circuit carry away any disturbances, leaving behind only the desirable quantum mechanical vibrations. Further, in order to avoid thermal disturbance, the experiment was conducted at the extremely low temperature of 273 °C, close to absolute zero.

"This is a wonderful example of how truly exploratory research can yield useful results and, eventually, products that can be used in the real world", said John Magan, FET project officer at the European Commission

Indeed, the discovery means a huge step for science, and the results have been published in Nature, the leading scientific journal. Entanglement serves as a cornerstone of quantum mechanics, an area of physics that is helping to develop the quantum technologies of the future, such as quantum computation and information transmission. One day, research into entanglement may possibly lead to sci-fi ideas such as teleportation becoming a reality.

"In the future, we will attempt to teleport the mechanical vibrations. In quantum teleportation, the properties of physical bodies can be transmitted across arbitrary distances using entanglement. We are still pretty far from Star Trek, though", said Dr Caspar Ockeloen-Korppi, the lead author of the published results of the work, who also performed the measurements.

The experiment was carried out at the OtaNano national research site for micro- and nanotechnologies in Finland. The HOT research team included scientists from the University of New South Wales in Australia, the University of Chicago in the USA, and the University of Jyväskylä in Finland. It was funded by the European Research Council, the EU's Horizon 2020 research and innovation programme, and the Academy of Finland.

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