An optical sensor based on a quantum algorithm is created

(ORDO NEWS) — Scientists from the Laboratory of Physics of Quantum Information Technologies at the Moscow Institute of Physics and Technology, together with an employee of the Argonne National Laboratory (USA), have implemented a modern quantum algorithm for measuring physical quantities using simple optical instruments. The results of the study bring the appearance of affordable high-precision sensors based on linear optics, which can be used in a variety of scientific fields: from astronomy to biology.

The work was published in the journal Scientific Reports. The sensitivity of measuring instruments is the most important characteristic in all fields of science and technology: astronomers need to accurately detect distant cosmic phenomena, biologists need to distinguish the smallest organic structures, and engineers need to measure the positions or speeds of various objects.

Until very recently, none of the existing measuring devices could provide accuracy above the so-called shot noise limit – a limitation due to the statistical features of classical measurements.

However, with the advent of quantum technology, it became possible to circumvent this barrier and reach the highest Heisenberg accuracy limit, which, in turn, is explained by the basic principles of quantum mechanics. An example of LIGO (an observatory where gravitational waves were detected several years ago) shows that Heisenberg sensitivity can be achieved by combining complex optical interference schemes with quantum technologies.

The latest field of physics – quantum metrology – is studying the technical and algorithmic tools for performing high-precision quantum measurements. Physicists from MIPT and Argonne National Laboratory decided to combine the methods of quantum metrology with linear optics.

“We came up with and built an optical circuit that performs the phase estimation procedure based on the Fourier transform,” says one of the authors of the article, Nikita Kirsanov from MIPT. – This procedure is the main component of many well-known quantum algorithms; including it is used in high-precision measuring protocols.”

An experimental setup consisting of a very large number of linear optical elements (beam splitters, phase plates, and mirrors) allows one to obtain information on geometric angles, positions, velocities, and other parameters of physical objects. To measure this or that quantity, it is necessary to “encode” it into optical phases directly measured in the experiment.

“This work is a continuation of our research in the field of universal quantum measurement algorithms,” says project manager Gordey Lesovik, head of the Laboratory of Physics of Quantum Information Technologies at MIPT. “Earlier, together with a Finnish group from Aalto University, we experimentally implemented a similar measurement algorithm, but based on transmon qubits.”

The experiment showed that, despite the large number of optical elements, the interference circuit can be tuned and controlled. In addition, according to the theoretical estimates given in the article, by means of linear optics it is possible to implement operations of even much greater complexity. Thus, scientists have shown that linear optics is an affordable and effective platform for the implementation of moderate-sized quantum measurement and computational operations.


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