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The hybrid interferometer integrating an optical parametric amplifier and a beam splitter has the potential to outperform the SU(1,1) interferometer. However, photon loss remains a critical limitation for practical implementation. To…

Quantum Physics · Physics 2025-10-21 Qisi Zhou , Tao Jiang , Qingqian Kang , Teng Zhao , Xin Su , Cunjin Liu , Liyun Hu

We propose Alternating Phase-Field Fourier Neural Networks (APF-FNNs) as a unified and physics-based framework for topology optimization. The approach decouples the design problem by representing the state, adjoint, and topology fields with…

Optimization and Control · Mathematics 2026-01-27 Jing Li , Xindi Hu , Helin Gong , Wei Gong , Shengfeng Zhu

We propose a high-precision phase estimation scheme in a hybrid interferometer by synergistically combining a Kerr nonlinear phase shifter and multi-photon subtraction operations. Using a coherent state and a vacuum state as input…

Quantum Physics · Physics 2026-05-21 Lifen Guo , Qingqian Kang , Zekun Zhao , Jifeng Sun , Teng Zhao , Cunjin Liu , Xin Su , Liyun Hu

We optimize two-mode, entangled, number states of light in the presence of loss in order to maximize the extraction of the available phase information in an interferometer. Our approach optimizes over the entire available input Hilbert…

Squeezed light enables quantum-enhanced phase estimation, with crucial applications in both fundamental physics and emerging technologies. To fully exploit the advantage provided by this approach, estimation protocols must remain optimal…

Quantum Physics · Physics 2025-10-17 Giorgio Minati , Enrico Urbani , Nicolò Spagnolo , Valeria Cimini , Fabio Sciarrino

We study the connection between exceptional points (EPs) and optimal parameter estimation, in a simple system consisting of two counter-propagating traveling wave modes in a microring resonator. The unknown parameter to be estimated is the…

Quantum Physics · Physics 2025-11-18 Robert L. Cook , Liwen Ko , K. Birgitta Whaley

We experimentally demonstrate a general criterion to identify entangled states useful for the estimation of an unknown phase shift with a sensitivity higher than the shot-noise limit. We show how to exploit this entanglement on the examples…

In a conventional atomic interferometer employing $N$ atoms, the phase sensitivity is at the standard quantum limit: $1/\sqrt{N}$. Using spin-squeezing, the sensitivity can be increased, either by lowering the quantum noise or via phase…

Quantum Physics · Physics 2020-06-24 Renpeng Fang , Resham Sarkar , Selim M. Shahriar

Quantum devices for generating entangled states have been extensively studied and widely used. As so, it becomes necessary to verify that these devices truly work reliably and efficiently as they are specified. Here, we experimentally…

Quantum-enhanced sensing is commonly benchmarked using the quantum Fisher information (QFI), often interpreted as a direct indicator of achievable precision. However, this quantity acquires operational meaning only within a fully specified…

Quantum Physics · Physics 2026-03-10 Zdeněk Hradil , Jaroslav Řeháček

Phase-insensitive optical amplifiers uniformly amplify each quadrature of an input field and are of both fundamental and technological importance. We find the quantum limit on the precision of estimating the gain of a quantum-limited…

Quantum Physics · Physics 2022-05-09 Ranjith Nair , Guo Yao Tham , Mile Gu

We consider the general problem of estimating an unknown control parameter of an open quantum system. We establish a direct relation between the evolution of both system and environment and the precision with which the parameter can be…

Quantum Physics · Physics 2016-02-10 Katarzyna Macieszczak , Madalin Guta , Igor Lesanovsky , Juan P. Garrahan

Interferometric phase estimation is an essential tool for precise measurements of quantities such as displacement, velocity and material properties. The lower bound on measurement uncertainty achievable with classical resources is set by…

Quantum Physics · Physics 2024-07-23 Shakib Daryanoosh , Geoff J. Pryde , Howard M. Wiseman , Sergei Slussarenko

Quantum metrology promises measurement precision beyond the classical limit by using suitably tailored quantum states and detection strategies. However, scaling up this advantage is experimentally challenging, due to the difficulty of…

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…

Quantum Physics · Physics 2026-03-27 Stefan Evans , Joanna Ptasinski

Two-photon absorption (TPA) is a nonlinear optical process with wide-ranging applications from spectroscopy to super-resolution imaging. Despite this, the precise measurement and characterisation of TPA parameters are challenging due to…

Quantum Physics · Physics 2023-11-22 Athena Karsa , Ranjith Nair , Andy Chia , Kwang-Geol Lee , Changhyoup Lee

We explore the advantages offered by twin light beams produced in parametric down-conversion for precision measurement. The symmetry of these bipartite quantum states, even under losses, suggests that monitoring correlations between the…

Quantum Physics · Physics 2010-07-20 Hugo Cable , Gabriel A. Durkin

We show that the quantum Cram\'er-Rao bound on the precision of measurements of the optical phase gradient, or the wavefront tilt, with a beam of finite width is consistent with the Heisenberg uncertainty principle for a single-photon…

Quantum Physics · Physics 2020-07-22 Walker Larson , Bahaa E. A. Saleh

We investigate the performance of entangled coherent state for quantum enhanced phase estimation. An exact analytical expression of quantum Fisher information is derived to show the role of photon losses on the ultimate phase sensitivity.…

Quantum Physics · Physics 2014-04-07 Y. M. Zhang , X. W. Li , W. Yang , G. R. Jin

The problem of estimating an unknown phase $ \varphi $ using two-level probes in the presence of unital phase-covariant noise and using finite resources is investigated. We introduce a simple model in which the phase-imprinting operation on…

Quantum Physics · Physics 2016-10-05 Rosanna Nichols , Thomas R. Bromley , Luis A. Correa , Gerardo Adesso