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The maximally entangled states are excellent candidates for achieving Heisenberg-limited measurements in ideal quantum metrology, however, they are fragile against dissipation such as particle losses and their achievable precisions may…

Quantum Physics · Physics 2016-02-05 Jiahao Huang , Xizhou Qin , Honghua Zhong , Yongguan Ke , Chaohong Lee

Squeezing of collective atomic spins has been shown to improve the sensitivity of atomic clocks and magnetometers to levels significantly below the standard quantum limit. In most cases the requisite atom-atom entanglement has been…

Bayesian inference is a powerful paradigm for quantum state tomography, treating uncertainty in meaningful and informative ways. Yet the numerical challenges associated with sampling from complex probability distributions hampers Bayesian…

Quantum Physics · Physics 2020-05-04 Joseph M. Lukens , Kody J. H. Law , Ajay Jasra , Pavel Lougovski

We identify the large-$N$ scaling of the metrological quantum gain offered by over-squeezed spin states that are accessible by one-axis-twisting, as a function of the preparation time. We further determine how the scaling is modified by…

Quantum Physics · Physics 2022-02-03 Y. Baamara , A. Sinatra , M. Gessner

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 address local quantum estimation of bilinear Hamiltonians probed by Gaussian states. We evaluate the relevant quantum Fisher information (QFI) and derive the ultimate bound on precision. Upon maximizing the QFI we found that single- and…

Quantum Physics · Physics 2009-11-13 Roberto Gaiba , Matteo G A Paris

We describe an optimized, self-correcting procedure for the Bayesian inference of pure quantum states. By analyzing the history of measurement outcomes at each step, the procedure returns the most likely pure state, as well as the optimal…

Quantum Physics · Physics 2015-09-14 Amir Kalev , Itay Hen

Quantum phase estimation based on Gaussian states plays a crucial role in many application fields. In this paper, we study the precision bound for the scheme using two-mode squeezed Gaussian states. The quantum Fisher information is…

Quantum Physics · Physics 2024-11-27 Jian-Dong Zhang , Chuang Li , Lili Hou , Shuai Wang

Interactions among sensors can provide, in addition to entanglement, an important resource for boosting the precision in quantum estimation protocols. Dephasing noise, however, remains a leading source of decoherence in state-of-the-art…

Quantum Physics · Physics 2025-01-03 Francisco Riberi , Lorenza Viola

Quantum entanglement, in the form of spin squeezing, is known to improve the sensitivity of atomic instruments to static or slowly-varying quantities. Sensing transient events presents a distinct challenge, requires different analysis…

Quantum Physics · Physics 2025-10-31 Julia Amoros-Binefa , Morgan W. Mitchell , Jan Kolodynski

As a crucial resource in the field of quantum metrology, spin squeezing can facilitate highly precise measurements that surpass the limitations imposed by classical physics. However, the quantum advantage of spin squeezing is significantly…

Quantum Physics · Physics 2026-05-13 Lin Jiao , Han Pu , Jun-Hong An

Nuclear magnetic resonance (NMR) experiments can reveal local properties in materials, but are often limited by the low signal-to-noise ratio. Spin squeezed states have an improved resolution below the Heisenberg limit in one of the spin…

Non-vanishing fluctuations of the vacuum state are a salient feature of quantum theory. These fluctuations fundamentally limit the precision of quantum sensors. Nowadays, several systems such as optical clocks, gravitational wave detectors,…

We present a quantum optimal control protocol to generate highly spin-squeezed states in Rydberg atom arrays coupled via Ising-type van der Waals interactions. Using gradient-based optimization techniques, we construct time-dependent pulse…

Quantum Physics · Physics 2025-12-01 Edison S. Carrera , Harold Erbin , Grégoire Misguich

This paper explores the sensitivity gains afforded by spin-squeezed states in atom interferometry, in particular using Bragg diffraction. We introduce a generalised input-output formalism that accurately describes realistic, non-unitary…

Quantum Physics · Physics 2026-05-29 Julian Günther , Jan-Niclas Kirsten-Siemß , Naceur Gaaloul , Klemens Hammerer

Cavity optomechanical (COM) sensors, enhanced by quantum squeezing or entanglement, have become powerful tools for measuring ultra-weak forces with high precision and sensitivity. However, these sensors usually rely on linear COM couplings,…

Realisation of experiments even on small and medium-scale quantum computers requires an optimisation of several parameters to achieve high-fidelity operations. As the size of the quantum register increases, the characterisation of quantum…

Quantum Physics · Physics 2020-08-11 F. Martínez-García , D. Vodola , M. Müller

Quantum phase estimation protocols can provide a measuring method of phase shift with precision superior to standard quantum limit (SQL) due to the application of a nonclassical state of light. A squeezed vacuum state, whose variance in one…

Quantum Physics · Physics 2020-04-14 Juan Yu , Yue Qin , Jinliang Qin , Hong Wang , Zhihui Yan , Xiaojun Jia , Kunchi Peng

Interferometers are crucial for precision measurements, including gravitational waves, laser ranging, radar, and imaging. The phase sensitivity, the core parameter, can be quantum-enhanced to break the standard quantum limit (SQL) using…

Quantum Physics · Physics 2023-02-22 Wenfeng Huang , Xinyun Liang , Baiqiang Zhu , Yuhan Yan , Chun-Hua Yuan , Weiping Zhang , Liqing Chen

Bragg interferometers, operating using pseudospin-1/2 systems composed of two momentum states, have become a mature technology for precision measurements. State-of-the-art Bragg interferometers are rapidly surpassing technical limitations…

Atomic Physics · Physics 2019-07-25 Athreya Shankar , Leonardo Salvi , Maria Luisa Chiofalo , Nicola Poli , Murray J Holland