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Multipartite entanglement, such as witnessed through the quantum Fisher information (QFI), is a crucial resource for quantum technologies, but its experimental certification is highly challenging. Here, we propose an experimentally friendly…

Quantum Physics · Physics 2021-09-01 Ricardo Costa de Almeida , Philipp Hauke

Determining the phase in one arm of a quantum interferometer is discussed taking into account the three non-ideal aspects in real experiments: non-deterministic state preparation, non-unitary state evolution due to losses during state…

Quantum Physics · Physics 2015-05-20 Thomas B. Bahder

Recent advancements have revealed new links between information geometry and classical stochastic thermodynamics, particularly through the Fisher information (FI) with respect to time. Recognizing the non-uniqueness of the quantum Fisher…

Quantum Physics · Physics 2025-10-07 Laetitia P. Bettmann , John Goold

Critical quantum systems are a promising resource for quantum metrology applications, due to the diverging susceptibility developed in proximity of phase transitions. Here, we assess the metrological power of parametric Kerr resonators…

Quantum Physics · Physics 2023-03-30 R. Di Candia , F. Minganti , K. V. Petrovnin , G. S. Paraoanu , S. Felicetti

Quantum optical systems comprising quantum emitters interacting with engineered optical modes generate non-classical states of light that can be used as resource states for quantum-enhanced interferometry. However, outside of…

Quantum Physics · Physics 2025-09-03 Erfan Abbasgholinejad , Daniel Malz , Ana Asenjo-Garcia , Rahul Trivedi

We consider the impact that temporal correlations in the measurement statistics can have on the achievable precision in a sequential metrological protocol. In this setting, and for a single quantum probe, we establish that it is the…

Quantum Physics · Physics 2024-04-02 Eoin O'Connor , Steve Campbell , Gabriel T. Landi

We consider the estimation of an unknown parameter $\theta$ through a quantum probe at thermal equilibrium. The probe is assumed to be in a Gibbs state according to its Hamiltonian $H_\theta$, which is divided in a parameter-encoding term…

Quantum Physics · Physics 2026-01-23 Paolo Abiuso , Pavel Sekatski , John Calsamiglia , Martí Perarnau-Llobet

We study multi-parameter sensing of 2D and 3D vector fields within the Bayesian framework for $SU(2)$ quantum interferometry. We establish a method to determine the optimal quantum sensor, which establishes the fundamental limit on the…

Quantum Physics · Physics 2023-06-05 Raphael Kaubruegger , Athreya Shankar , Denis V. Vasilyev , Peter Zoller

We run a numerical linked-cluster expansion with a quantum algorithm (NLCE+QA), computing ground-state energies and one quasi-particle dispersions in the thermodynamic limit using a 20-qubit trapped-ion quantum processing unit (QPU). The…

Quantum Physics · Physics 2026-05-28 Lucas Marti , Sumeet , Stefan Wolf , K. P. Schmidt , Michael J. Hartmann

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

We investigate the limits of thermometry using quantum probes at thermal equilibrium within the Bayesian approach. We consider the possibility of engineering interactions between the probes in order to enhance their sensitivity, as well as…

We introduce a positive Hermitian operator, the Fisher operator, and use it to examine a measurement process incorporating unitary dynamics and complete measurements. We develop the idea of information complement, the minimization of which…

Quantum Physics · Physics 2009-02-20 Gabriel A. Durkin

Accurate characterization of quantum systems is essential for the development of quantum technologies, particularly in the noisy intermediate-scale quantum (NISQ) era. While traditional methods for Hamiltonian learning and noise…

Quantum Physics · Physics 2025-07-18 Gubio G. de Lima , Iann Cunha , Leonardo Kleber Castelano

We apply noise thermometry to characterize charge and thermoelectric transport in single InAs nanowires (NWs) at a bath temperature of 4.2 K. Shot noise measurements identify elastic diffusive transport in our NWs with negligible…

Mesoscale and Nanoscale Physics · Physics 2016-10-03 E. S. Tikhonov , D. V. Shovkun , V. S. Khrapai , D. Ercolani , F. Rossella , M. Rocci , L. Sorba , S. Roddaro

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

Quantum metrology studies the use of entanglement and other quantum resources to improve precision measurement. An interferometer using N independent particles to measure a parameter X can achieve at best the "standard quantum limit" (SQL)…

Quantum Physics · Physics 2012-03-06 M. Napolitano , M. Koschorreck , B. Dubost , N. Behbood , R. J. Sewell , M. W. Mitchell

We present a method to estimate the quantum Fisher information (QFI) of many-body quantum states in the presence of decoherence, where its direct evaluation requires the full spectral resolution of the density matrix. We show that, for…

Quantum Physics · Physics 2026-05-25 Francesco Musso , Vittorio Vitale , Sara Murciano

Based on the conventional Mach-Zehnder interferometer, we propose a metrological scheme to improve phase sensitivity. In this scheme, we use a coherent state and a squeezed vacuum state as input states, employ multi-photon-subtraction…

Quantum Physics · Physics 2025-05-08 Qisi Zhou , Qinqian Kang , Tao Jiang , Zekun Zhao , Teng Zhao , Cunjin Liu , Liyun Hu

We propose an entanglement-enhanced sensing scheme that is robust against spatially inhomogeneous always-on Ising interactions. Our strategy is to tailor coherent quantum dynamics employing the Hilbert-space fragmentation (HSF), a recently…

Quantum Physics · Physics 2022-11-18 Atsuki Yoshinaga , Yuichiro Matsuzaki , Ryusuke Hamazaki

We characterize operationally meaningful quantum gains in a paradigmatic model of lossless multiple-phase interferometry and stress insufficiency of the analysis based solely on the concept of quantum Fisher information. We show that the…

Quantum Physics · Physics 2022-01-28 Wojciech Gorecki , Rafal Demkowicz-Dobrzanski