A New Quantum-Inspired Optical Sensor

Researchers from the Moscow Institute of Physics and Tech­nology, joined by a colleague from Argonne National Laboratory, U.S., have imple­mented an advanced quantum algorithm for measuring physical quantities using simple optical tools. Their study takes us a step closer to af­fordable linear optics-based sensors with high performance charac­teristics. Such tools are sought after in diverse research fields, from astronomy to biology.

Part of the experiment for measuring the position of an object using optical coherence alone. (Source: N. Kirsanov, MIPT)

Maximizing the sensitivity of measure­ment tools is crucial for any field of science and tech­nology. Astronomers seek to detect remote cosmic phenomena, biologists need to discern ex­ceedingly tiny organic structures, and engineers have to measure the positions and velo­cities of objects, to name a few examples. Until recently, no measure­ment tool could ensure precision above the shot noise limit, which has to do with the statistical features inherent in classical obser­vations. Quantum technology has provided a way around this, boosting precision to the fundamental Heisenberg limit, stemming from the basic principles of quantum mechanics.

The LIGO experiment, which detected gravi­tational waves for the first time in 2016, shows it is possible to achieve Heisenberg-limited sensi­tivity by combining complex optical inter­ference schemes and quantum techniques. Quantum metrology is a cutting-edge area of physics concerned with the technological and algorithmic tools for making highly precise quantum measure­ments. Now, the team from MIPT and ANL fused quantum metrology with linear optics.

“We devised and constructed an optical scheme that runs the Fourier transform-based phase estimation procedure,” said Nikita Kirsanov from MIPT. “This procedure lies at the core of many quantum algorithms, including high-precision measure­ment protocols.” A specific arrange­ment of a very large number of linear optical elements – beam splitters, phase shifters, and mirrors – makes it possible to gain information about the geometric angles, positions, velo­cities as well as other parameters of physical objects. The measure­ment involves encoding the quantity of interest in the optical phases, which are then deter­mined directly.

“This research is a follow-up to our work on universal quantum measurement algo­rithms,” commented principal inves­tigator Gordey Lesovik, who heads the MIPT Laboratory of the Physics of Quantum Information Technology. “In an earlier collaboration with a research group from Aalto University in Finland, we experi­mentally implemented a similar measurement algo­rithm on transmon qubits.”

The experiment showed that despite the large number of optical elements in the scheme, it is nevertheless tunable and controllable. According to the theo­retical estimates provided in the paper linear optics tools are viable for implementing even operations that are consi­derably more complex. “The study has demonstrated that linear optics offers an affordable and effective platform for implementing moderate-scale quantum measurements and compu­tations,” said Argonne Distinguished Fellow Valerii Vinokur. (Source: MIPT)

Reference: V. V. Zemlyanov et al.: Phase estimation algorithm for the multibeam optical metrology, Sci. Rep. 10, 8715 (2020); DOI: 10.1038/s41598-020-65466-3

Link: Laboratory of the Physics of Quantum Information Technology, Moscow Institute of Physics and Technology, Moscow, Russia

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