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A variational approach based on the multi-coherent-state ansatz with asymmetric parameters is employed to study the ground state of the spin-boson model. Without any artificial approximations except for the finite number of the coherent…

Quantum Gases · Physics 2014-12-22 Liwei Duan , Shu He , Qing-Hu Chen

In this paper we present a study of the quantum phase estimation problem employing continuous-variable, entangled squeezed coherent (quasi-Bell) states as probe states. We show that their inherent squeezing and entanglement properties might…

Quantum Physics · Physics 2022-11-01 Douglas Delgado de Souza , A. Vidiella-Barranco

Quantum effects in metrology can in principle enhance measurement precision from the so-called standard quantum limit to the Heisenberg Limit. Further advancements in quantum metrology largely rely on innovative metrology protocols that can…

Quantum Physics · Physics 2025-06-16 Zhixing Zou , Jiangbin Gong , Weitao Chen

Armed with quantum correlations, quantum sensors in a network have shown the potential to outclass their classical counterparts in distributed sensing tasks such as clock synchronization and reference frame alignment. On the other hand,…

Quantum Physics · Physics 2024-05-24 Yuxiang Yang , Benjamin Yadin , Zhen-Peng Xu

Entanglement asymmetry provides a quantitative measure of symmetry breaking in many-body quantum states. Focusing on inhomogeneous $U(1)$ charges, such as dipole and multipole moments, we show that the typical asymmetry is bounded by a…

Statistical Mechanics · Physics 2026-04-10 Lorenzo Gotta , Filiberto Ares , Sara Murciano

Quantum Metrology calculates the ultimate precision of all estimation strategies, measuring what is their root mean-square error (RMSE) and their Fisher information. Here, instead, we ask how many bits of the parameter we can recover,…

Quantum Physics · Physics 2017-11-22 Lorenzo Maccone , Majid Hassani , Chiara Macchiavello

We analyze the dynamics of entanglement entropy in a generic quantum many-body open system from the perspective of quantum information and error corrections. We introduce a random unitary circuit model with intermittent projective…

Quantum Physics · Physics 2020-07-17 Soonwon Choi , Yimu Bao , Xiao-Liang Qi , Ehud Altman

The classical bound on image resolution defined by the Rayleigh limit can be beaten by exploiting the properties of quantum mechanical entanglement. If entangled photons are used as signal states, the best possible resolution is instead…

Quantum Physics · Physics 2009-11-13 G. Gilbert , M. Hamrick , Y. S. Weinstein , S. P. Pappas , A. Donadio

The use of quantum resources can provide measurement precision beyond the shot-noise limit (SNL). The task of ab initio optical phase measurement---the estimation of a completely unknown phase---has been experimentally demonstrated with…

The resources needed to conventionally characterize a quantum system are overwhelmingly large for high- dimensional systems. This obstacle may be overcome by abandoning traditional cornerstones of quantum measurement, such as general…

Quantum Physics · Physics 2016-05-17 Gregory A. Howland , Samuel H. Knarr , James Schneeloch , Daniel J. Lum , John C. Howell

Many protocols require precise rotation measurement. Here we present a general class of states that surpass the shot noise limit for measuring rotation around arbitrary axes. We then derive a quantum Cram\'er-Rao bound for simultaneously…

Quantum Physics · Physics 2019-03-20 Aaron Z. Goldberg , Daniel F. V. James

We explore optical quantum engineering of phase-parameterized continuous-variable (CV) probe states to exploit nonclassical light to solve the problem of precise phase estimation. The optical interferometer consists of a single beam…

Quantum Physics · Physics 2026-03-11 Mikhail S. Podoshvedov , Sergey A. Podoshvedov

We investigate an optimal distance of two components in an entangled coherent state for quantum phase estimation in lossy interferometry. The optimal distance is obtained by an economical point, representing the quantum Fisher information…

Quantum Physics · Physics 2020-01-28 Su-Yong Lee , Yong Sup Ihn , Zaeill Kim

We derive fundamental lower bounds on the performance of optical metrology and communication systems in a Bayesian framework. The derivation uses classical rate-distortion theory in conjunction with bounds on the capacity to transmit…

Quantum Physics · Physics 2018-09-24 Ranjith Nair

Quantum phase estimation is one of the critical building blocks of quantum computing. For early fault-tolerant quantum devices, it is desirable for a quantum phase estimation algorithm to (1) use a minimal number of ancilla qubits, (2)…

Quantum Physics · Physics 2023-11-08 Hongkang Ni , Haoya Li , Lexing Ying

Achieving the ultimate precisions for multiple parameters simultaneously is an outstanding challenge in quantum physics, because the optimal measurements for incompatible parameters cannot be performed jointly due to the Heisenberg…

Quantum Physics · Physics 2023-10-12 Binke Xia , Jingzheng Huang , Hongjing Li , Han Wang , Guihua Zeng

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

We show that the phase sensitivity $\Delta \theta$ of a Mach-Zehnder interferometer fed by a coherent state in one input port and squeezed-vacuum in the other one is i) independent from the true value of the phase shift and ii) can reach…

Quantum Physics · Physics 2009-11-13 L. Pezze' , A. Smerzi

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

Quantum chaotic and integrable systems are known to exhibit a characteristic $1/f$ and $1/f^{2}$ noise, respectively, in the power spectrum associated to their spectral fluctuations. A recent work [R. Riser, V. A. Osipov, and E. Kanzieper,…

Quantum Physics · Physics 2019-09-17 A. L. Corps , A. Relaño