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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

We derive a bound on the precision of state estimation for finite dimensional quantum systems and prove its attainability in the generic case where the spectrum is non-degenerate. Our results hold under an assumption called local asymptotic…

Quantum Physics · Physics 2019-05-09 Yuxiang Yang , Giulio Chiribella , Masahito Hayashi

Trace distance and infidelity (induced by square root fidelity), as basic measures of the closeness of quantum states, are commonly used in quantum state discrimination, certification, and tomography. However, the sample complexity for…

Quantum Physics · Physics 2024-10-29 Qisheng Wang , Zhicheng Zhang

We generalize the experimental success criterion for quantum teleportation/memory in continuous-variable quantum systems to be suitable for non-unit-gain condition by considering attenuation/amplification of the coherent-state amplitude.…

Quantum Physics · Physics 2008-09-29 Ryo Namiki , Masato Koashi , Nobuyuki Imoto

We define and study a fidelity criterion for quantum channels, which we term the minimax fidelity, through a noncommutative generalization of maximal Hellinger distance between two positive kernels in classical probability theory. Like…

Quantum Physics · Physics 2009-11-10 Viacheslav P. Belavkin , Giacomo Mauro D'Ariano , Maxim Raginsky

We investigate the problem of bounding the quantum process fidelity given bounds on the fidelities between target states and the action of a process on a set of pure input states. We formulate the problem as a semidefinite program and prove…

Quantum Physics · Physics 2018-11-28 Karl Mayer , Emanuel Knill

The so-called "threshold" theorem says that, once the error rate per qubit per gate is below a certain value, indefinitely long quantum computation becomes feasible, even if all of the qubits involved are subject to relaxation processes,…

Quantum Physics · Physics 2007-06-13 M. I. Dyakonov

Superior computational power promised by quantum computers utilises the fundamental quantum mechanical principle of entanglement. However, achieving entanglement and verifying that the generated state does not follow the principle of local…

Coherence and correlation are key features of the quantum system. Quantifying these quantities are astounding task in the framework of resource theory of quantum information processing. In this article, we identify an affinity-based metric…

Quantum Physics · Physics 2021-02-11 R. Muthuganesan , V. K. Chandrasekar , R. Sankaranarayanan

It is not a problem to complement a classical bit, i.e. to change the value of a bit, a 0 to a 1 and vice versa. This is accomplished by a NOT gate. Complementing a qubit in an unknown state, however, is another matter. We show that this…

Quantum Physics · Physics 2007-05-23 V. Buzek , M. Hillery , R. Werner

Recently quantum states discrimination has been frequently studied. In this paper we study them from the other way round, the likeness of two quantum states. The fidelity is used to describe the likeness of two quantum states. Then we…

Quantum Physics · Physics 2009-11-07 Fei Xue , Jiangfeng Du , Xianyi Zhou , Rongdian Han , Jihui Wu

Fidelity estimation for entangled states constitutes an essential building block for quality control and error detection in quantum networks. Nonetheless, quantum networks often encounter heterogeneous and correlated noise, leading to…

Quantum Physics · Physics 2024-11-18 Liangzhong Ruan , Bas Dirkse

We derive a universal performance limit for coherent quantum control in the presence of modeled and unmodeled uncertainties. For any target unitary $W$ that is implementable in the absence of error, we prove that the worst-case (and hence…

Quantum Physics · Physics 2025-07-14 Robert L. Kosut , Daniel A. Lidar , Herschel Rabitz

We study the quantitative characterization of the performance of qubit measurements in this paper. In particular, the back-action evading nature of quantum nondemolition (QND) readout of qubits is fully quantified by quantum trace distance.…

Quantum Physics · Physics 2022-08-16 He Wang , Ya Cao

Fault-tolerant quantum computation requires non-destructive quantum measurements with classical feed-forward. Many experimental groups are actively working towards implementing such capabilities and so they need to be accurately evaluated.…

Quantum Physics · Physics 2023-06-14 Darian McLaren , Matthew A. Graydon , Joel J. Wallman

We study dynamical decoupling in a multi-qubit setting, where it is combined with quantum logic gates. This is illustrated in terms of computation using Heisenberg interactions only, where global decoupling pulses commute with the…

Quantum Physics · Physics 2008-08-14 K. Khodjasteh , D. A. Lidar

We consider several definitions of the quantum Wasserstein distance based on an optimization over general bipartite quantum states with given marginals. Then, we examine the quantities obtained after the optimization is carried out over…

Quantum Physics · Physics 2026-05-15 Géza Tóth , József Pitrik

Efforts to scale-up quantum computation have reached a point where the principal limiting factor is not the number of qubits, but the entangling gate infidelity. However, the highly detailed system characterization required to understand…

We propose a series of quantum algorithms for computing a wide range of quantum entropies and distances, including the von Neumann entropy, quantum R\'{e}nyi entropy, trace distance, and fidelity. The proposed algorithms significantly…

Quantum Physics · Physics 2024-07-29 Qisheng Wang , Ji Guan , Junyi Liu , Zhicheng Zhang , Mingsheng Ying

This document focuses on translating various information-theoretic measures of distinguishability for probability distributions into measures of distin- guishability for quantum states. These measures should have important appli- cations in…

Quantum Physics · Physics 2007-05-23 Christopher A. Fuchs