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Classical learning of the expectation values of observables for quantum states is a natural variant of learning quantum states or channels. While learning-theoretic frameworks establish the sample complexity and the number of measurement…

Quantum Physics · Physics 2024-08-12 Beng Yee Gan , Po-Wei Huang , Elies Gil-Fuster , Patrick Rebentrost

Quantum-dense metrology (QDM) constitutes a special case of quantum metrology in which two orthogonal phase space projections of a signal are simultaneously sensed beyond the shot noise limit. Previously it was shown that the additional…

Quantum Physics · Physics 2016-11-02 Melanie Ast , Sebastian Steinlechner , Roman Schnabel

Quantum noise sets a fundamental limit to the sensitivity of high-precision measurements. Suppressing it can be achieved by using non-classical states and quantum filters, which modify both the noise and signal response. We find a novel…

Quantum Physics · Physics 2021-03-09 Joe Bentley , Hendra Nurdin , Yanbei Chen , Haixing Miao

Increasingly sophisticated programmable quantum simulators and quantum computers are opening unprecedented opportunities for exploring and exploiting the properties of highly entangled complex quantum systems. The complexity of large…

Quantum communication theory sets the maximum rates at which information can be encoded and decoded reliably given the physical properties of the information carriers. Here we consider the problem of readout of a digital optical memory,…

Quantum Physics · Physics 2013-07-18 Cosmo Lupo , Stefano Pirandola , Vittorio Giovannetti , Stefano Mancini

Image classification is a core task of intelligent sensing, conventionally follows a sequential imaging then processing pipeline. However, redundant high-dimensional image reconstruction is inherently inefficient, especially in photon…

Quantum parameter estimation is central to many fields such as quantum computation, communications and metrology. Optimal estimation theory has been instrumental in achieving the best accuracy in quantum parameter estimation, which is…

Quantum Physics · Physics 2015-06-18 Shibdas Roy , Ian R. Petersen , Elanor H. Huntington

We demonstrate a method for super-resolving signals encoded as finite mixtures of bosonic modes using collective measurements that exploit permutation symmetry. Specifically, we use multiple copies of the state $\rho$ of the finite mixture…

Quantum Physics · Physics 2025-11-06 J. O. de Almeida , M. Lewenstein , M. Skotiniotis

We study quantum measurement with preselection and postselection, and derive the precise expressions of the measurement results without any restriction on the coupling strength between the system and the measuring device. For a qubit…

Quantum Physics · Physics 2011-11-18 Xuanmin Zhu , Yuxiang Zhang , Shengshi Pang , Chang Qiao , Quanhui Liu , Shengjun Wu

The problem of estimating an unknown phase $ \varphi $ using two-level probes in the presence of unital phase-covariant noise and using finite resources is investigated. We introduce a simple model in which the phase-imprinting operation on…

Quantum Physics · Physics 2016-10-05 Rosanna Nichols , Thomas R. Bromley , Luis A. Correa , Gerardo Adesso

The quantum Cram\'er-Rao bound (QCRB) provides an ultimate precision limit allowed by quantum mechanics in parameter estimation. Given any quantum state dependent on a single parameter, there is always a positive-operator valued measurement…

Quantum Physics · Physics 2020-07-21 Sisi Zhou , Chang-Ling Zou , Liang Jiang

Phase estimation protocols provide a fundamental benchmark for the field of quantum metrology. The latter represents one of the most relevant applications of quantum theory, potentially enabling the capability of measuring unknown physical…

In quantum metrology, one of the major applications of quantum technologies, the ultimate precision of estimating an unknown parameter is often stated in terms of the Cram\'er-Rao bound. Yet, the latter is no longer guaranteed to carry an…

We introduce new rounding methods to improve the accuracy of finite precision quantum arithmetic. These quantum rounding methods are applicable when multiple samples are being taken from a quantum program. We show how to use multiple…

Quantum Physics · Physics 2021-08-18 Rajiv Krishnakumar , William Zeng

Quantum sensors have the potential to outperform their classical counterparts. For classical sensing, the uncertainty of the estimation of the target fields scales inversely with the square root of the measurement time T. On the other hand,…

Quantum Physics · Physics 2018-05-09 Yuichiro Matsuzaki , Simon Benjamin , Shojun Nakayama , Shiro Saito , William J. Munro

Classical shadow tomography has become a powerful tool in learning about quantum states prepared on a quantum computer. Recent works have used classical shadows to variationally enforce N-representability conditions on the 2-particle…

Quantum error correction can reduce the effects of noise in quantum systems, e.g. in metrology or most notably in quantum computing. Typically, this requires making measurements that provide information about the errors that have occurred…

Quantum Physics · Physics 2024-12-12 Christian Wimmer , Jochen Szangolies , Michael Epping

In this paper, we consider the generalized measurement where one particular quantum signal is unambiguously extracted from a set of non-commutative quantum signals and the other signals are filtered out. Simple expressions for the maximum…

Quantum Physics · Physics 2009-11-10 Masahiro Takeoka , Masashi Ban , Masahide Sasaki

Emerging sonography techniques often imply increasing in the number of transducer elements involved in the imaging process. Consequently, larger amounts of data must be acquired and processed by the beamformer. The significant growth in the…

Other Computer Science · Computer Science 2012-01-06 Noam Wagner , Yonina C. Eldar , Arie Feuer , Zvi Friedman

Quantum metrology explores optimal quantum protocols for parameter estimation. In the context of optical atomic clocks, conventional protocols focus on optimal input states and measurements to achieve enhanced sensitivities. However, such…

Quantum Physics · Physics 2025-09-03 Su Direkci , Manuel Endres , Tuvia Gefen