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Measurement incompatibility is a cornerstone of quantum mechanics. In the context of estimating multiple parameters of a quantum system, this manifests as a fundamental trade-off between the precisions with which different parameters can be…

Quantum Physics · Physics 2025-11-11 Simon K. Yung , Aritra Das , Jun Suzuki , Ping Koy Lam , Jie Zhao , Lorcán O. Conlon , Syed M. Assad

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

In this work, we develop a quantum metrological framework for quantum chaos by showing that local subsystems of information scrambling systems naturally function as quantum stopwatches. The reduced quantum state of a subsystem encodes the…

Quantum Physics · Physics 2026-04-01 Devjyoti Tripathy , Federico Centrone , Sebastian Deffner

Quantum phase estimation (QPE) is a cornerstone of quantum algorithms designed to estimate the eigenvalues of a unitary operator. QPE is typically implemented through two paradigms with distinct circuit structures: quantum Fourier…

Quantum Physics · Physics 2026-03-16 Ryosuke Kimura , Kosuke Mitarai

For a fixed average energy, the simultaneous estimation of multiple phases can provide a better total precision than estimating them individually. We show this for a multimode interferometer with a phase in each mode, using Gaussian inputs…

Quantum Physics · Physics 2016-11-03 Christos N. Gagatsos , Dominic Branford , Animesh Datta

The Cram\'er-Rao bound serves as a crucial lower limit for the mean squared error of an estimator in frequentist parameter estimation. Paradoxically, it requires highly accurate prior knowledge of the estimated parameter for constructing…

Quantum Physics · Physics 2025-04-21 Javier Navarro , Ricard Ravell Rodríguez , Mikel Sanz

The Quantum Fisher information (QFI) quantifies the ultimate precision of estimating a parameter from a quantum state, and can be regarded as a reliability measure of a quantum system as a quantum sensor. However, estimation of the QFI for…

Quantum Physics · Physics 2022-02-03 Jacob L. Beckey , M. Cerezo , Akira Sone , Patrick J. Coles

In statistical estimation theory, it has been shown previously that the Wigner-Yanase skew information is bounded by the quantum Fisher information associated with the phase parameter. Besides, the quantum Cram\'er-Rao inequality is…

Quantum Physics · Physics 2023-01-18 Nour-Eddine Abouelkhir , Hanane EL Hadfi , Abdallah Slaoui , Rachid Ahl Laamara

As a method to extract information from optical system, imaging can be viewed as a parameter estimation problem. The fundamental precision in locating one emitter or estimating the separation between two incoherent emitters is bounded below…

Quantum Physics · Physics 2021-07-29 Ben Wang , Liang Xu , Lijian Zhang

A scheme is proposed to estimate the system and environmental parameter, the detuning, temperature and the squeezing strength with a high precision by the two-level atom system. It hasn't been reported that the squeezing strength estimation…

Quantum Physics · Physics 2021-05-07 Mengmeng Luo , Wenxiao Liu , Yuetao Chen , Shaoyan Gao

The quantum Fisher information, the quantum analogue of the classical Fisher information, is a central quantity in quantum metrology and quantum sensing due to its connection to parameter estimation and fidelity susceptibility. Using…

Variance and Fisher information are ingredients of the Cramer-Rao inequality. We regard Fisher information as a Riemannian metric on a quantum statistical manifold and choose monotonicity under coarse graining as the fundamental property of…

Quantum Physics · Physics 2009-11-07 Denes Petz

To any parametric family of states of a finite level quantum system we associate a space of Fisher maps and introduce the natural notions of Cram\'er-Rao-Bhattacharya tensor and Fisher information form. This leads us to an abstract…

Probability · Mathematics 2009-07-14 K. R. Parthasarathy

Biphoton frequency comb (BFC), which encompasses multiple discrete frequency modes and represents high-dimensional frequency entanglement, is crucial in quantum information processing due to its high information capacity and error…

Quantum Physics · Physics 2025-07-30 Baihong Li , Qi-qi Li , Boxin Yuan , Ruifang Dong , Shougang Zhang , Rui-Bo Jin

Quantum Fisher information characterizes the phase sensitivity of qubits in the spin-boson model with a finite bandwidth spectrum. In contrast with Markovian reservoirs, the quantum Fisher information will flow from the environments to…

Quantum Physics · Physics 2015-06-18 Xiang Hao , Ninghua Tong , Shiqun Zhu

Precision measurement has been an important research area in sensing and metrology. In classical physics, the Fisher information determines the maximum extractable information from statistically unknown signals, based on a joint probability…

Quantum Physics · Physics 2024-09-04 Byoung S. Ham

We investigate whether collider experiments can reach the quantum limit of precision, defined by the quantum Fisher information (QFI), using only classical observables such as particle momenta. As a case study, we focus on the…

High Energy Physics - Phenomenology · Physics 2025-12-17 Tengyu Ai , Qi Bi , Yuxin He , Jia Liu , Xiao-Ping Wang

The quantum Cram\'er-Rao (QCR) bound sets the ultimate local precision limit for unbiased multiparameter estimation. Yet, unlike in the single-parameter case, its saturability is not generally guaranteed and is often assessed through…

Quantum Physics · Physics 2026-02-13 Satoya Imai , Jing Yang , Luca Pezzè

We deal with the maximization of classical Fisher information in a quantum system depending on an unknown parameter. This problem has been raised by physicists, who defined [Helstrom (1967) Phys. Lett. A 25 101-102] a quantum counterpart of…

Statistics Theory · Mathematics 2007-06-13 Alessandra Luati

Quantum sensing enables the ultimate precision attainable in parameter estimation. Circumstantial evidence suggests that certain organisms, most notably migratory songbirds, also harness quantum-enhanced magnetic field sensing via a…

Quantum Physics · Physics 2026-04-17 Luke D. Smith , Jonas Glatthard , Farhan T. Chowdhury , Daniel R. Kattnig