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Distinct from closed quantum systems, non-Hermitian system can have exceptional points (EPs) where both eigenvalues and eigenvectors coalesce. Recently, it has been proposed and demonstrated that EPs can enhance the performance of sensors…

Quantum Physics · Physics 2019-11-05 Mengzhen Zhang , William Sweeney , Chia Wei Hsu , Lan Yang , A. D. Stone , Liang Jiang

Generally, natural scientific problems are so complicated that one has to establish some effective perturbation or nonperturbation theories with respect to some associated ideal models. In this Letter, a new theory that combines…

Computational Physics · Physics 2015-05-13 Yuan Gao , S. Y. Lou

We derive a bound on the precision of state estimation for finite dimensional quantum systems and prove its attainability in the generic case where the spectrum is non-degenerate. Our results hold under an assumption called local asymptotic…

Quantum Physics · Physics 2019-05-09 Yuxiang Yang , Giulio Chiribella , Masahito Hayashi

We develop generalized bounds for quantum single-parameter estimation problems for which the coupling to the parameter is described by intrinsic multi-system interactions. For a Hamiltonian with $k$-system parameter-sensitive terms, the…

Quantum Physics · Physics 2007-05-23 Sergio Boixo , Steven T. Flammia , Carlton M. Caves , JM Geremia

Pushing the boundaries of measurement precision is central for sensing and metrology, pursued by nonclassical resources such as squeezing, and non-Hermitian degeneracies with distinct spectral response. Their convergence, however, remains…

In this paper, we analyze the finite sample complexity of stochastic system identification using modern tools from machine learning and statistics. An unknown discrete-time linear system evolves over time under Gaussian noise without…

Machine Learning · Computer Science 2019-03-22 Anastasios Tsiamis , George J. Pappas

Identifying the Hamiltonian of a quantum system from experimental data is considered. General limits on the identifiability of model parameters with limited experimental resources are investigated, and a specific Bayesian estimation…

Quantum Physics · Physics 2019-10-15 S. G. Schirmer , F. C. Langbein

Quantum sensing harnesses the unique properties of quantum systems to enable precision measurements of physical quantities such as time, magnetic and electric fields, acceleration, and gravitational gradients well beyond the limits of…

Quantum Physics · Physics 2025-07-23 Ivana Nikoloska , Ruud Van Sloun , Osvaldo Simeone

Quantum enhanced sensing provides a powerful tool for the precise measurement of physical parameters that is applicable in many areas of science and technology. The achievable gain in sensitivity is largely limited by the influence of noise…

Quantum Physics · Physics 2016-12-07 Yu Liu , Zijun Shu , Martin B. Plenio , Jianming Cai

Quantum phenomena offer the possibility of measuring physical quantities with precision beyond classical limits. However, current progress is constrained by scalability, environmental noise, and challenges in practical integration. This…

Quantum Physics · Physics 2025-10-24 George Mihailescu , Uesli Alushi , Roberto Di Candia , Simone Felicetti , Karol Gietka

Developing superior quantum sensing strategies ranging from ultra-high precision measurement to complex structural analysis is at the heart of quantum technologies. While strategies using quantum resources, such as entanglement among…

Advancing quantum sensing tools for investigating systems at atomic and nanoscales is crucial for the progress of quantum technologies. While numerous protocols employ quantum probes to extract information from stationary or weakly coupled…

Quantum Physics · Physics 2025-06-12 Martin Kuffer , Analía Zwick , Gonzalo A. Álvarez

Models based on non-Hermitian Hamiltonians can exhibit a range of surprising and potentially useful phenomena. Physical realizations typically involve couplings to sources of incoherent gain and loss; this is problematic in quantum…

Quantum Physics · Physics 2019-07-03 Yu-Xin Wang , A. A. Clerk

Dynamical instabilities can amplify small perturbations into measurable signals, offering a route to quantum-enhanced sensing. This mechanism was experimentally demonstrated in a collective-spin system with quadratic interactions, described…

Quantum Physics · Physics 2026-04-08 Bidhi Vijaywargia , Jorge Chávez-Carlos , Francisco Pérez-Bernal , Lea F. Santos

Quantum metrology enhances the sensitivity of parameter estimation using the distinctive resources of quantum mechanics such as entanglement. It has been shown that the precision of estimating an overall multiplicative factor of a…

Quantum Physics · Physics 2016-05-31 Shengshi Pang , Todd A. Brun

There has been debate around applicability of exceptional points (EP) for quantum sensing. To resolve this, we first explore how to experimentally implement the nonhermitian non-diagonalizable Hamiltonians, that exhibit EPs, in quantum…

Quantum Physics · Physics 2024-01-15 Chetan Waghela , Shubhrangshu Dasgupta

Estimating the eigenvalues of non-normal matrices is a foundational problem with far-reaching implications, from modeling non-Hermitian quantum systems to analyzing complex fluid dynamics. Yet, this task remains beyond the reach of standard…

Quantum Physics · Physics 2025-10-23 Yukun Zhang , Yusen Wu , Xiao Yuan

Bayesian estimation is a powerful theoretical paradigm for the operation of quantum sensors. However, the Bayesian method for statistical inference generally suffers from demanding calibration requirements that have so far restricted its…

Quantum Physics · Physics 2021-09-22 Samuel P. Nolan , Augusto Smerzi , Luca Pezzè

Quantum-enhanced metrology surpasses classical metrology by improving estimation precision scaling with a resource $N$ (e.g., particle number or energy) from $1/\sqrt{N}$ to $1/N$. Through the use of nonlinear effects, Roy and…

Quantum Physics · Physics 2025-04-07 Noah Lordi , John Drew Wilson , Murray J. Holland , Joshua Combes

The theoretical framework for networked quantum sensing has been developed to a great extent in the past few years, but there are still a number of open questions. Among these, a problem of great significance, both fundamentally and for…

Quantum Physics · Physics 2020-06-18 Jesús Rubio , Paul A Knott , Timothy J Proctor , Jacob A Dunningham