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Quantum Communications and Quantum Imaging

Enhancing fiber optic gyroscope precision using polarization-entangled two-photon states

Stefan Evans, Joanna Ptasinski

Published Sep 18, 2025• 0 citations
Publisher

Abstract

We determine the feasibility of enhancing fiber optic gyroscope (FOG) precision using polarization-entangled two-photon states. Additional non-reciprocal effects beyond those encountered in classical FOGs arise in the entangled setup. We analyze a N00N state FOG setup combining features of two recent experiments, while optimizing the fiber length and mitigating noise sources to ensure sufficient quantum enhancement to see beyond the shot noise limit. We expect our setup to further advance the sensitivity regime of such single-photon detector based (low power requirement) FOGs, which have recently resolved the earth’s rotation rate.

DOI
10.1117/12.3067835

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We determine the feasibility of enhancing fiber optic gyroscope (FOG) precision using polarization-entangled two-photon states. Additional non-reciprocal effects beyond those encountered in classical FOGs arise in the entangled setup. We analyze a N00N state FOG setup combining features of two recent experiments, while optimizing the fiber length and mitigating noise sources to ensure sufficient quantum enhancement to see beyond the shot noise limit. We expect our setup to further advance the sensitivity regime of such single-photon detector based (low power requirement) FOGs, which have recently resolved the earth’s rotation rate.
Abstract Fiber optic gyroscopes (FOG) based on the Sagnac effect are a valuable tool in sensing and navigation and enable accurate measurements in applications ranging from spacecraft and aircraft to self-driving vehicles such as autonomous cars. As with any classical optical sensors, the ultimate performance of these devices is bounded by the shot-noise limit (SNL). Quantum-enhanced interferometry allows us to overcome this limit using non-classical states of light. Here, we report on an entangled-photon gyroscope that uses path-entangled NOON-states (N = 2) to provide super-resolution and phase sensitivity beyond the shot-noise limit.
We analyze noise in a quantum-enhanced fiber optic gyroscope (FOG), focusing on one of the leading sources of phase uncertainty—uncorrelated photon saturation. Taking a squeezed state input as a source for N00N states, we compute the uncorrelated false coincidence counts at the optimal phase bias and determine an upper limit to the squeezed amplitude ξ which allows for sub-shot noise precision. As examples, we apply parameters of present-day quantum FOG experiments and determine the maximum possible precision enhancement based on their respective ξ and optimal phase bias points. With the aim of supporting future FOG setups with higher N00N state fluxes, our result highlights the need to transition to multimode states to bypass the ξ limitation, such as photon pairs generated by the dynamical Casimir effect.
Quantum techniques, developed in recent decades, provide new approaches to achieving high-precision measurements beyond the classical bounds. In this paper, we theoretically demonstrate a metrology method for improving the sensitivity of the interferometric optical gyroscope, robust against the loss, by using coherent-light stimulated two-mode squeezed beams as the light source. The detection protocol is based on a simple intensity measurement, and the quantum noise is far below the shot-noise limit. The enhancement factors for different coherent light fields are analyzed in detail. Additionally, the influence of loss during the propagation in the optical path is studied, and the conditions for achieving sub-shot-noise measurement sensitivity are obtained. We also find that the phase sensitivity of the proposed gyroscope scheme becomes closer to the quantum Cramér-Rao bound with increasing of the photon number of the coherent beams.
We evaluate the fundamental performance of a fiber-optic gyroscope (FOG) design that is enhanced by the injection of a quantum-optical squeezed vacuum. In the presence of fiber loss, we compute the optimum attainable enhancement below the standard quantum limit in terms of the angular velocity estimator variance from a homodyne measurement. We find that currently realizable amounts of single-mode squeezing are sufficient to access the maximum quantitative improvement, but that this gain in maximum rotation sensitivity is limited to a marginal constant factor. We then propose an entanglement-enhanced FOG design that segments a fixed amount of available fiber into multiple fiber interferometers and feeds this sensor array with a multimode-entangled squeezed vacuum resource. Our design raises the fundamental improvement in sensitivity to an appreciable factor of $e\ensuremath{\approx}2.718$.
This paper derives the principle of the photon-entangled fiber gyro’s optical path, simulates and compares the effect of the rotation angle of the half-wave plate (HWP) optical axis on the output state quantum interference efficiency, and performs a simulation analysis of the polarization entanglement error in the photon-entangled fiber gyro. It is proven that the rotation angle of the half-wave plate’s optical axis has a significant impact on the quantum interference efficiency, with the maximum quantum interference efficiency corresponding to a half-wave plate optical axis rotation angle of 22.5°. When there is a deviation in the rotation angles of the two half-wave plates, it does not lead to non-reciprocal phase errors.Still, it lowers quantum interference efficiency and increases measurement difficulty. Excessive errors in the rotation angle of the half-wave plate’s optical axis may reduce the accuracy performance of the gyroscope. The polarization error generated by the entire optical path may lead to the inability to break through the shot noise limit (SNL), and in the case of existing background noise, the polarization error has a more severe impact on the accuracy of the entangled gyroscope.
The advent of increasingly precise gyroscopes has played a key role in the technological development of navigation systems. Ring-laser and fiber-optic gyroscopes, for example, are widely used in modern inertial guidance systems and rely on the interference of unentangled photons to measure mechanical rotation. The sensitivity of these devices scales with the number of particles used as 1/N1/\sqrt{N}1/N​. Here we demonstrate how, by using sources of entangled particles, it is possible to do better and even achieve the ultimate limit allowed by quantum mechanics where the precision scales as 1/N1/N1/N. We propose a gyroscope scheme that uses ultracold atoms trapped in an optical ring potential.