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Quantum Electronics

Noise-oriented quantum optical gyrometry

Ivan I. Krasionov, L. V. Il’ichev

Published Feb 1, 2022• 0 citations
Publisher

Abstract

Abstract By the example of an optical gyroscope scheme, a new method for improving the accuracy of phase measurements is considered. In the rotation-recording Mach – Zehnder interferometer, a two-mode squeezed vacuum is used as an input state. This does not allow realising the traditional scheme, since the average value of the difference signal at the output is always zero. However, it is shown that information about the magnitude of the rotation angular velocity of the instrument reference frame is contained in the noise level of the difference signal. The possibility of reaching the Heisenberg limit of the measurement accuracy is demonstrated.

DOI
10.1070/qel17979

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Abstract By the example of an optical gyroscope scheme, a new method for improving the accuracy of phase measurements is considered. In the rotation-recording Mach – Zehnder interferometer, a two-mode squeezed vacuum is used as an input state. This does not allow realising the traditional scheme, since the average value of the difference signal at the output is always zero. However, it is shown that information about the magnitude of the rotation angular velocity of the instrument reference frame is contained in the noise level of the difference signal. The possibility of reaching the Heisenberg limit of the measurement accuracy is demonstrated.
Phase measurement using a lossless Mach–Zehnder interferometer with certain entangled N-photon states can lead to a phase sensitivity of the order of 1/N, the Heisenberg limit. However, previously considered output measurement schemes are different for different input states to achieve this limit. We show that it is possible to achieve this limit just by the parity measurement for all the commonly proposed entangled states. Based on the parity measurement scheme, the reductions of the phase sensitivity in the presence of photon loss are examined for the various input states.
Abstract A scheme is proposed based on a Mach–Zehnder interferometer with high phase sensitivity, utilizing a two-mode squeezed coherent state, generated by four-wave mixing, as input. The phase sensitivity of this scheme easily surpasses the Heisenberg limit when intensity difference detection is applied. Under phase-matching conditions, the quantum Cramér–Rao bound significantly exceeds the Heisenberg limit. Additionally, the scheme exhibits robustness against photon loss. When compared with the modified SU(1,1) interferometer with two coherent state inputs, this approach demonstrates superior measurement sensitivity, evaluated through various detection methods and the quantum Cramér–Rao bound. This work holds potential applications in quantum metrology.
Recent developments in quantum technologies have enabled significant improvements in the precision of optical sensing systems. This work explores the integration of distributed quantum sensing with optical gyroscopes to improve the estimation accuracy of angular velocity. Utilizing bright two-mode squeezed states (bTMSS), which offer high photon numbers and strong bipartite quantum correlations, we propose a configuration that leverages continuous-variable entanglement across multiple spatially separated optical gyroscopes. Unlike traditional quantum sensing that enhances a single sensor, our approach focuses on estimating a global phase shift—corresponding to the average angular rotation—across distributed optical gyroscopes with quantum-enhanced sensitivity. We analyze the phase sensitivities of different bTMSS configurations, including mode entangled bTMSS and separable M -bTMSS, and evaluate their performance through the quantum Cramér-Rao bound. The analysis shows that, with 5 % photon loss in every channel in the system, the proposed scheme shows a sensitivity enhancement of ∼ 9.3 dB beyond the shot-noise limit, with an initial squeezing of ∼ 9.8 dB . The present scheme has potential applications in quantum-enhanced inertial navigation and precision metrology within emerging quantum networks.
There has been much interest in improving gyroscope precision with quantum technology for realizing autonomous navigation. The laser light in coherent state cannot reach higher precision under shot-noise limit (SNL) caused by vacuum zero energy fluctuation, which restricts the further improvement of optical gyroscope precision. Quantum mechanics reckons that one unused port of the beam splitter (BS) is inputted with vacuum, which results in vacuum fluctuation, while another port is inputted with the laser light in optical gyroscope. In order to compress the vacuum fluctuation, we design an experimental scheme, in which squeezed vacuum light is used as another incident light into the unused port of Sagac interferometer in optical gyroscope. We analyze the physical process of this scheme theoretically and develop the quantum balanced homodyne detection technique to retrieve the relative phase information of Sagac interferometer output. There are two most important conditions that we should pay attention to. 1) We should ensure that the phase of local oscillator light arg(α L), the phase of coherent light arg (αc) and the angle of squeezed direction arg(μν) in the squeezed vacuum light satisfy the condition, i.e., arg (α L2)-arg (μν) = πup and arg (α L)-arg (αc) = 0 when we perform quantum balanced homodyne detection technique for the best sensitivity δφ = e-GδφSNL, where G denotes the squeezed degree; 2) only by deriving the fields from one common source can we ensure coherence among the squeezed vacuum, probe and local oscillator. Although the requirements for experimental settings are strict, we can meet the requirement with careful calibration. Numerical analysis shows that this proposed scheme provides much higher precision below SNL: both sensitivity detection limit and dynamic range grow with an exponential rate as the squeezed degree grows. The current technology for squeezed vacuum generation by using two consecutive crystals with the optic axes tilted allows us to reach a value as high as G ≈ 16 of squeezed degree. Only by inputting such squeezed vacuum light into the unused port of BS in the optical gyroscope, can we attain sensitivity detection limit and dynamic range with increment by 108. Our approach is a new scheme for improving optical gyroscope with current available technology.
A “hybrid” atomic–optical scheme of an interferometer–gyroscope has been proposed and investigated. It is based on the ring configuration of a Bose–Einstein condensate that is intercepted by an additional potential barrier or well. This ring configuration defect is created by a nonresonant radiation beam that interacts dispersively with the atoms located in its region. The beam propagates along one of the arms of a Mach–Zehnder interferometer. The rotation of the gyrometer reference system modifies the state of the condensate due to the mentioned potential defect and it, in turn, changes the conditions of interference of radiation interacting with atoms. In contrast to the well-known ideas of using the Bose–Einstein condensate in gyrometry, which imply the destruction of the condensate in order to directly observe its interference, the proposed scheme ideally operates without the loss of atoms by the condensate. The efficiency of the scheme has been estimated for realistic conditions.