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Identification of nonorthogonal quantum states without error is crucial for various applications in quantum information technology, as well as the foundations of quantum physics. Theoretical studies have proposed measurements that maximize…

Quantum Physics · Physics 2026-03-11 Kang-Min Hu , Min Namkung , Myung-Hyun Sohn , Hyang-Tag Lim

We address the problem of continuous-variable quantum phase estimation in the presence of linear disturbance at the Hamiltonian level, by means of Gaussian probe states. In particular we discuss both unitary and random disturbance, by…

Quantum Physics · Physics 2015-01-26 Douglas Delgado de Souza , Marco G. Genoni , M. S. Kim

We propose a method for quantum enhanced phase estimation based on continuous variable (CV) quantum teleportation. The phase shift probed by a coherent state can be enhanced by repeatedly teleporting the state back to interact with the…

In many real-world problems, recovering sparse signals from underdetermined linear systems remains a fundamental challenge. Although $\ell_1$ norm minimization is widely used, it suffers from estimation bias that prevents it from reaching…

Information Theory · Computer Science 2026-04-16 Keisuke Morita , Federico Ricci-Tersenghi , Masayuki Ohzeki

Photon counting induces an effective nonlinear optical phase shift on certain states derived by linear optics from single photons. Although this no nlinearity is nondeterministic, it is sufficient in principle to allow scalable linear…

Quantum Physics · Physics 2007-05-23 T. C. Ralph , A. P. Lund , H. M. Wiseman

This thesis presents three studies in quantum-enhanced sensing and target detection. The first study explores covert target detection using optical or microwave probes, establishing quantum-mechanical limits on the error probabilities of…

Quantum Physics · Physics 2024-10-16 Guo Yao Tham

Bayesian error analysis paves the way to the construction of credible and plausible error regions for a point estimator obtained from a given dataset. We introduce the concept of region accuracy for error regions (a generalization of the…

Quantum Physics · Physics 2019-07-15 Changhun Oh , Yong Siah Teo , Hyunseok Jeong

As a signal recovery algorithm, compressed sensing is particularly useful when the data has low-complexity and samples are rare, which matches perfectly with the task of quantum phase estimation (QPE). In this work we present a new…

Quantum Physics · Physics 2025-01-01 Changhao Yi , Cunlu Zhou , Jun Takahashi

The performance of key tasks in quantum technology, such as accurate state preparation, can be maximized by utilizing external controls and deriving their shape with optimal control theory. For non-pure target states, the performance…

Quantum Physics · Physics 2019-03-13 Daniel Basilewitsch , Christiane P. Koch , Daniel M. Reich

We provide the optimal measurement strategy for a class of noisy channels that reduce to the identity channel for a specific value of a parameter (spreading channels). We provide an example that is physically relevant: the estimation of the…

Quantum Physics · Physics 2022-12-21 Wojciech Górecki , Alberto Riccardi , Lorenzo Maccone

We investigate the ultimate precision limits for quantum phase estimation in terms of the coherence, $C$, of the probe. For pure states, we give the minimum estimation variance attainable, $V(C)$, and the optimal state, in the asymptotic…

Quantum Physics · Physics 2022-07-13 D. Munoz-Lahoz , J. Calsamiglia , J. A. Bergou , E. Bagan

Quantum noise constitutes a fundamental obstacle to realizing practical quantum technologies. To address the pivotal challenge of identifying quantum systems least affected by noise, we introduce the purest quantum state identification,…

Quantum Physics · Physics 2025-09-24 Yingqi Yu , Honglin Chen , Jun Wu , Wei Xie , Xiangyang Li

We have previously [Phys. Rev. A 65, 043803 (2002)] analyzed adaptive measurements for estimating the continuously varying phase of a coherent beam, and a broadband squeezed beam. A real squeezed beam must have finite photon flux N and…

Quantum Physics · Physics 2007-05-23 Dominic W. Berry , Howard M. Wiseman

Phase estimation in quantum interferometry is a major scenario where the quantum advantage is significantly revealed. Recently, the optimal finite-dimensional probe states (OFPSs) for phase estimation in two-mode quantum interferometry have…

Quantum Physics · Physics 2026-05-07 Jin-Feng Qin , Jing Liu

Quantum parameter estimation holds significant promise for achieving high precision through the utilization of the most informative measurements. While various lower bounds have been developed to assess the best accuracy for estimates, they…

Quantum Physics · Physics 2024-07-19 Jianchao Zhang , Jun Suzuki

Quantum metrology and sensing seek advantage in estimating an unknown parameter of some quantum state or channel, using entanglement such as spin squeezing produced by one-axis twists or other quantum resources. In particular, qubit phase…

Quantum Physics · Physics 2024-05-29 Tyler G. Thurtell , Akimasa Miyake

Von Neumann projections are the main operations by which information can be extracted from the quantum to the classical realm. They are however static processes that do not adapt to the states they measure. Advances in the field of adaptive…

Quantum Physics · Physics 2015-10-28 Amine Laghaout , Ulrik L. Andersen

This dissertation studies the statistics and modeling of a quantum system probed by a coherent laser field. We focus on an ensemble of qubits dispersively coupled to a traveling wave light field. The first research topic explores the…

Quantum Physics · Physics 2013-01-29 Robert L. Cook

In this article we propose a method to estimate with high accuracy pure quantum states of a single qudit. Our method is based on the minimization of the squared error between the complex probability amplitudes of the unknown state and its…

Quantum Physics · Physics 2021-07-14 A. Rojas , L. Pereira , S. Niklitschek , A. Delgado

Absorption measurement is an exceptionally versatile tool for many applications in science and engineering. For absorption measurements using laser beams of light, the sensitivity is theoretically limited by the shot noise due to the…

Optics · Physics 2021-04-22 Fu Li , Tian Li , Marlan O. Scully , Girish S. Agarwal