Secure quantum communications for the first time in the range of microwaves

Framed within the great European project of the Quantum Flagship, led by Mikel Ruiz Sanchez, researcher of the group QUTIS of the Department of Physical Chemistry of the UPV / EHU, have carried out an experiment in collaboration with German and Japanese researchers where they have managed to develop a protocol of preparation of a quantum state at a distance, but making communication in the range of microwaves, “which is the frequency in which all quantum computers work. This is the first time that the possibility of doing it in this range has been verified, which can bring a revolution in the coming years in the fields of safe quantum communication and quantum microwave radars, “comments the researcher who leads the experiment published in Nature Communications.
The preparation of a remote quantum state (known in English as remote state preparation) is based on the phenomenon of quantum entanglement, in which the sets of particles that are intertwined lose their individuality and behave as a single entity, even if they are spatially separated.
The studies with this protocol of preparation of a quantum state at a distance began about 20 years ago, but to date the communication had always been made by waves of the visible range. “This is because work in this range can be performed at room temperature, since the thermal radiation emitted by the bodies, simply by being at room temperature, is extremely low in the optical range, so that There are interferences in that communication, the researcher describes. However, in the range of microwaves, billions, trillions of photons are produced at room temperature that destroy the quantum properties, so to avoid all that noise, these experiments must be done at temperatures close to absolute zero (0.05). Kelvin), to limit the radiation of bodies to the maximum, and communication is effective “.
After a great work in the development of that technology to be able to do the experiments, they managed to prepare a quantum state at a distance of 35 centimeters. “This has been a proof of concept, which in English is known as proof of principle, a first step to know that it is possible to move forward in the development of this technology. But we believe that it is a very important first step, which can bring about a revolution in the next decade “, highlights Dr. Sanz. The researcher highlights two areas in which this revolution could occur: “on the one hand, communication or quantum cryptography, since it would be absolutely safe, and by not having to change the frequency to the optical range (as it is currently done), many losses in that communication would be avoided. And on the other hand, ultra-precise quantum metrology and quantum radars. The different applications that radars have are based on the detection of objects, and this detection is done in microwaves, and since there are devices such as drones that are getting smaller, it is required that radars have more and more power to be able to detect them, to know where they are. The technology we are developing can help a lot in this regard. ” These applications, and many others that this technology can have, are not conceivable in the low temperatures in which they work today, so “one of the objectives of the project is to try to get this technology to work at room temperature. After all, what we are looking for is to bring this technology to commercial products, “concludes Sanz.

S. Pogorzalek, K.G. Fedorov, M. Xu, A. Parra-Rodriguez, M. Sanz, M. Fischer, E. Xie, K. Inomata, Y. Nakamura, E. Solano, A. Marx, F. Deppe, R. Gross

Secure quantum remote state preparation of squeezed microwave states

Nature Communications (2019)

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