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In the study of quantum computation, data is represented in terms of linear operators which form a generalized model of probability, and computations are most commonly described as products of unitary transformations, which are the…

Quantum Physics · Physics 2008-12-16 Jonathan Robert Niel de Beaudrap

We describe algorithms, and experimental strategies, for the Pareto optimal control problem of simultaneously driving an arbitrary number of quantum observable expectation values to their respective extrema. Conventional quantum optimal…

Quantum Physics · Physics 2009-11-13 Raj Chakrabarti , Rebing Wu , Herschel Rabitz

One of the main quests in quantum metrology, and quantum parameter estimation in general, is to find out the highest achievable precision with given resources and design schemes that attain that precision. In this article we present a…

Quantum Physics · Physics 2016-05-23 Haidong Yuan , Chi-Hang Fred Fung

We investigate quantum state discrimination with confidentiality. $N$ observers share a given quantum state belonging to a finite set of known states. The observers want to determine the state as accurately as possible and send a…

Quantum Physics · Physics 2015-06-30 Kenji Nakahira , Tsuyoshi Sasaki Usuda , Kentaro Kato

In quantum computing, knowing the symmetries a given system or state obeys or disobeys is often useful. For example, Hamiltonian symmetries may limit allowed state transitions or simplify learning parameters in machine learning…

Quantum Physics · Physics 2024-07-26 Margarite L. LaBorde , Soorya Rethinasamy , Mark M. Wilde

Variational quantum metrology represents a powerful tool for optimizing generic estimation strategies, combining the principles of variational optimization with the techniques of quantum metrology. Such optimization procedures result…

We propose a classification of measurement apparatuses based on their reliability and accessibility. Our notion of reliability parameterises the possibility of getting unexpected wrong results when using the apparatus in a given time…

Quantum Physics · Physics 2024-07-26 Nicola Pranzini , Paola Verrucchi

The performance of the quantum approximate optimization algorithm is evaluated by using three different measures: the probability of finding the ground state, the energy expectation value, and a ratio closely related to the approximation…

Quantum Physics · Physics 2020-06-08 Madita Willsch , Dennis Willsch , Fengping Jin , Hans De Raedt , Kristel Michielsen

Quantum metrology protocols are typically designed around the assumption that we have an abundance of measurement data, but recent practical applications are increasingly driving interest in cases with very limited data. In this regime the…

Quantum Physics · Physics 2019-04-18 Jesús Rubio , Jacob Dunningham

Observational entropy is interpreted as the uncertainty an observer making measurements associates with a system. So far, properties that make such an interpretation possible rely on the assumption of ideal projective measurements. We show…

Quantum Physics · Physics 2023-12-11 Dominik Šafránek , Juzar Thingna

We discuss the problem of finding the best measurement strategy for estimating the value of a quantum system parameter. In general the optimum quantum measurement, in the sense that it maximizes the quantum Fisher information and hence…

Quantum Physics · Physics 2017-02-07 Esteban Martinez , Carlos Pineda , François Leyvraz , Pablo Barberis-Blostein

Many-body quantum systems can exhibit collective effects that enhance the sensitivity of parameter estimation protocols. An example is provided by resonantly driven two-level atoms subject to collective dissipation, which can display a…

Quantum Physics · Physics 2026-03-24 Albert Cabot , Federico Carollo , Igor Lesanovsky

Quantum metric learning enhances machine learning by mapping classical data to a quantum Hilbert space with maximal separation between classes. However, on current NISQ hardware, this mapping process itself is prone to errors and could be…

Quantum Physics · Physics 2026-03-31 Ahmed Shokry , Movahhed Sadeghi , Mahmut Kandemir

We consider an adversarial Bayesian signal processing problem involving "us" and an "adversary". The adversary observes our state in noise; updates its posterior distribution of the state and then chooses an action based on this posterior.…

Signal Processing · Electrical Eng. & Systems 2020-02-19 Vikram Krishnamurthy , Muralidhar Rangaswamy

Experimental characterizations of a quantum system involve the measurement of expectation values of observables for a preparable state |psi> of the quantum system. Such expectation values can be measured by repeatedly preparing |psi> and…

Quantum Physics · Physics 2009-11-13 Emanuel Knill , Gerardo Ortiz , Rolando D. Somma

We consider the problem of characterizing the set of input-output correlations that can be generated by an arbitrarily given quantum measurement. Our main result is to provide a closed-form, full characterization of such a set for any qubit…

Quantum Physics · Physics 2017-06-26 Michele Dall'Arno , Sarah Brandsen , Francesco Buscemi , Vlatko Vedral

In a unified framework, we obtain two-sided estimates of the following quantities of interest in quantum information theory: 1.The minimum-error distinguishability of arbitrary ensembles of mixed quantum states. 2.The approximate…

Quantum Physics · Physics 2010-09-29 Jon Tyson

We consider process tomography for unitary quantum channels. Given access to an unknown unitary channel acting on a $\textsf{d}$-dimensional qudit, we aim to output a classical description of a unitary that is $\varepsilon$-close to the…

Quantum Physics · Physics 2024-07-31 Jeongwan Haah , Robin Kothari , Ryan O'Donnell , Ewin Tang

Recently, a novel framework for semi-device-independent quantum prepare-and-measure protocols has been proposed, based on the assumption of a limited distinguishability between the prepared quantum states. Here, we discuss the problem of…

Quantum Physics · Physics 2019-11-11 Weixu Shi , Yu Cai , Jonatan Bohr Brask , Hugo Zbinden , Nicolas Brunner

We address the issue of the discrimination between two-qubit amplitude damping channels by exploring several strategies. For the single-shot, we show that the excited state does not always give the optimal input, and that side entanglement…

Quantum Physics · Physics 2021-05-11 Milajiguli Rexiti , Stefano Mancini