Quantum Fiber Optic Gyroscopes Achieve Sub-Shot Noise Precision through Noise Mitigation

Quantum enhanced fiber optic gyroscopes promise significantly improved precision in measuring rotation, but achieving this potential requires overcoming inherent noise limitations. Stefan Evans and Joanna Ptasinski, both from the Naval Information Warfare Center Pacific, investigate a key source of uncertainty in these devices, specifically uncorrelated photon saturation. Their work identifies optimal operating conditions that minimise this noise, paving the way for sub-shot noise precision and ultimately, the development of gyroscopes capable of detecting incredibly subtle changes in angular rotation, far beyond current capabilities. This research represents a crucial step towards realising the full potential of quantum technology for advanced navigation and sensing applications.

Optimal ranges of phase bias angles minimise uncertainty, allowing for sub-shot noise precision measurements, enhancing the performance of fibre optic gyroscopes and potentially enabling the detection of extremely small angular rotations beyond the Earth’s rotation rate. Utilizing entangled photonic N00N states offers significant advantages over classical optical instruments, as their interference exhibits resolutions inaccessible through traditional methods.

Quantum Gyroscope Using Entangled Photon States

This document provides a comprehensive analysis of the principles, potential improvements, and noise considerations for a quantum fibre optic gyroscope (FOG). It details how leveraging quantum entanglement, specifically N00N states, can improve FOG performance by surpassing the classical shot noise limit and achieving higher precision in rotation measurements. The FOG operates by measuring the phase difference between two counter-propagating light beams within a fibre coil, where rotation induces this phase difference, and the research focuses on generating N00N states to enhance measurement accuracy. Maintaining the coherence and entanglement of N00N states is crucial for optimal performance, as any loss of these properties degrades the results.

Several noise sources can affect the accuracy of the FOG, including chromatic and polarization mode dispersion in the fibre, instabilities in the pump laser and SPDC source, and limitations arising from single photon saturation. To mitigate these issues, the research proposes using high-quality polarization-maintaining fibre, stabilizing the temperature of the nonlinear crystal, compensating for pump laser instabilities through signal processing, and carefully selecting the bias phase. Increasing fibre length could potentially enhance sensitivity, although it also increases the impact of dispersion. Single photon saturation is a central theme, as the limitations of single-photon detectors can distort the N00N state interference and introduce errors.

The proposed solution involves carefully selecting the bias phase to minimize this effect. The research also acknowledges the trade-off between sensitivity and dispersion when optimizing fibre length and suggests exploring longer fibre lengths, linear methods for generating entangled states, and more precise formulations of dispersion to further enhance the quantum FOG. Overall, this document represents a thorough investigation into the challenges and opportunities of developing high-precision quantum FOGs. It demonstrates a strong understanding of the underlying physics and engineering principles and emphasizes practical considerations and mitigation strategies. The clear identification of key challenges, such as single photon saturation and dispersion, makes this work particularly valuable for researchers in the field.

Phase Uncertainty Limits Fibre Optic Gyroscope Precision

Scientists have thoroughly evaluated phase uncertainty in enhanced fibre optic gyroscopes, focusing on the impact of uncorrelated photon coincidence counts, a primary source of error. Their work reveals that this uncertainty fluctuates as a function of phase bias, creating unstable points within the measurement. Through detailed analysis, the team identified stable domains centered on optimal bias points where instability remains below the level of shot noise, a fundamental limit in precision measurement. Applying this analysis to a leading quantum FOG experiment, researchers determined the spurious coincidence count rate and identified viable phase bias domains, refining the interpretation of both existing and future experimental measurements.

The findings demonstrate that phase errors remain negligible even near locations where sharp cusps in the phase shift occur, due to the larger shot noise in the experimental setup. Calculations based on previous experiments demonstrate that the achieved Sagnac phase uncertainty is below the classical shot noise limit. Looking ahead, scientists project that an upcoming quantum FOG experiment will achieve a similar spurious coincidence count rate to current performance. By carefully selecting phase bias points, researchers anticipate optimizing performance and achieving further enhancements in quantum FOG technology, potentially reducing phase uncertainty by over an order of magnitude.

Quantum Noise Mitigation in Fibre Gyroscopes

This research successfully evaluated quantum noise sources within fibre optic gyroscopes, specifically focusing on phase uncertainty arising from uncorrelated photon saturation. The team characterized optimal ranges for phase bias angles, demonstrating how to minimize instability and achieve precision beyond the classical shot noise limit. Applying this analysis to a current leading quantum FOG experiment, researchers identified viable phase bias domains, refining the interpretation of both existing and future experimental measurements and enabling the detection of smaller angular rotations. The findings demonstrate a potential reduction in phase uncertainty by over an order of magnitude, opening avenues for advancements in quantum FOG technology.

This improvement could facilitate the creation of higher order N00N states and the implementation of linear methods for generating entangled states, effectively mitigating the impact of single photon saturation. While acknowledging that future experiments utilizing larger uncorrelated to correlated photon ratios may require further corrections to coherence functions, this work provides a crucial foundation for enhancing the sensitivity and performance of fibre optic gyroscopes. The team intends to apply this analysis to an upcoming quantum FOG experiment, building upon previous work in the field.