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We generalize the approach by Braunstein and Caves [Phys. Rev. Lett. 72, 3439 (1994)] to quantum multi-parameter estimation with general states. We derive a matrix bound of the classical Fisher information matrix due to each measurement…

Quantum Physics · Physics 2019-09-10 Jing Yang , Shengshi Pang , Yiyu Zhou , Andrew N. Jordan

Quantum metrology employs quantum resources to achieve measurement precision beyond classical limits. This work investigates a Mach--Zehnder interferometer incorporating a Kerr nonlinear phase shifter, with photon-added two-mode squeezed…

Quantum Physics · Physics 2026-02-20 Zekun Zhao , Qingqian Kang , Teng Zhao , Cunjin Liu , Xin Su , Liyun Hu

As laser interferometer gravitational wave (GW) detectors become quantum noise dominated, understanding the fundamental limit on measurement sensitivity imposed by quantum uncertainty is crucial to guide the search for further noise…

Quantum Physics · Physics 2019-06-19 Belinda Pang , Yanbei Chen

Understanding the fundamental limits on the precision to which an optical phase can be estimated is of key interest for many investigative techniques utilized across science and technology. We study the estimation of a fixed optical phase…

Quantum Physics · Physics 2017-12-13 Patrick M. Birchall , Jeremy L. O'Brien , Jonathan C. F. Matthews , Hugo Cable

Multiparameter quantum metrology is essential for a wide range of practical applications. However, simultaneously achieving the ultimate precision for all parameters, as prescribed by the quantum Cram\'er-Rao bound (QCRB), remains a…

Quantum Physics · Physics 2025-09-15 Minghao Mi , Ben Wang , Lijian Zhang

Sensing and imaging are among the most important applications of quantum information science. To investigate their fundamental limits and the possibility of quantum enhancements, researchers have for decades relied on the quantum…

Quantum Physics · Physics 2016-08-24 Xiao-Ming Lu , Mankei Tsang

We introduce new formulations of the quantum Cram\'{e}r-Rao bound (QCRB) and the Holevo Cram\'{e}r-Rao bound (HCRB) in multi-parameter quantum metrology via purification, where we show their values for any mixed state are connected to that…

Quantum Physics · Physics 2026-05-06 Sisi Zhou

Quantum states of light can enable sensing configurations with sensitivities beyond the shot-noise limit (SNL). In order to better take advantage of available quantum resources and obtain the maximum possible sensitivity, it is necessary to…

Quantum Physics · Physics 2022-07-21 Mohammadjavad Dowran , Timothy S. Woodworth , Ashok Kumar , Alberto M. Marino

The fundamental quantum interferometry bound limits the sensitivity of an interferometer for a given total rate of photons and for a given decoherence rate inside the measurement device.We theoretically show that the recently reported…

Quantum Physics · Physics 2013-10-15 Rafal Demkowicz-Dobrzanski , Konrad Banaszek , Roman Schnabel

Ever since the inception of gravitational-wave detectors, limits imposed by quantum mechanics to the detection of time-varying signals have been a subject of intense research and debate. Drawing insights from quantum information theory,…

Quantum Physics · Physics 2012-10-17 Mankei Tsang , Ranjith Nair

Context: Ground-based telescopes are susceptible to seeing, an atmospheric phenomenon that reduces the resolving power of large observatories to that of a home telescope. Compensating these effects is therefore critical to realizing the…

Instrumentation and Methods for Astrophysics · Physics 2025-11-11 Jacob Trzaska , Amit Ashok

In multiparameter quantum metrology, the ultimate precision of joint estimation is dictated by the Holevo Cram\'er-Rao bound. In this paper, we discuss and analyze in detail an alternative approach: the stepwise estimation strategy. In this…

Quantum Physics · Physics 2025-10-23 Gabriele Fazio , Jiayu He , Matteo G. A. Paris

The theory of linear quantum measurement has been developed for analysing the sensitivities of experimental devices that measure extremely weak signals, such as gravitational waves. It has successfully contributed to the theoretical…

Quantum Physics · Physics 2019-11-25 Yiqiu Ma , Xiang Li , Shengjun Yang , Yanbei Chen

We analyse the precision limits for simultaneous estimation of a pair of conjugate parameters in a displacement channel using Gaussian probes. Having a set of squeezed states as an initial resource, we compute the Holevo Cram\'er-Rao bound…

Quantum Physics · Physics 2020-05-27 Syed M. Assad , Jiamin Li , Yuhong Liu , Ningbo Zhao , Wen Zhao , Ping Koy Lam , Z. Y. Ou , Xiaoying Li

The estimation of multiple parameters is a ubiquitous requirement in many quantum metrology applications. However, achieving the ultimate precision limit, i.e. the quantum Cram\'er-Rao bound, becomes challenging in these scenarios compared…

Quantum Physics · Physics 2024-11-25 Ben Wang , Kaimin Zheng , Qian Xie , Aonan Zhang , Liang Xu , Lijian Zhang

We solve the general problem of determining, through imaging, the three-dimensional positions of $N$ weak incoherent point-like emitters in an arbitrary spatial configuration. We show that a structured measurement strategy in which a linear…

Quantum Physics · Physics 2021-03-25 Cosmo Lupo , Zixin Huang , Pieter Kok

With the improvement in sensitivity of gravitational wave (GW) detectors and the increasing diversity of GW sources, there is a strong need for accurate GW waveform models for data analysis. While the current model accuracy assessments…

General Relativity and Quantum Cosmology · Physics 2022-08-22 Qian Hu , John Veitch

Interferometric imaging is an emerging technique for particle tracking and mass photometry. Mass or position are estimated from weak signals, coherently scattered from nanoparticles or single molecules, and interfered with a co-propagating…

High-precision sensors that exploit uniquely quantum phenomena have been shown to surpass the standard quantum limit of measurement precision. However, in the general scenario where multiple parameters are simultaneously encoded in a…

Quantum Physics · Physics 2025-10-20 Berihu Teklu , Victor Montenegro

A conventional resonant detector is often subject to a trade-off between bandwidth and peak sensitivity that can be traced back to quantum Cramer-Rao Bound. Anomalous dispersion has been shown to improve it by signal amplification and is…

Quantum Physics · Physics 2020-12-03 Xiang Li , Maxim Goryachev , Yiqiu Ma , Michael E. Tobar , Chunnong Zhao , Rana X Adhikari , Yanbei Chen