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Related papers: Using Qubits to Measure Fidelity in Mesoscopic Sys…

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In almost all quantum applications, one of the key steps is to verify that the fidelity of the prepared quantum state meets expectations. In this Letter, we propose a new approach solving this problem using machine-learning techniques.…

Quantum Physics · Physics 2021-09-28 Xiaoqian Zhang , Maolin Luo , Zhaodi Wen , Qin Feng , Shengshi Pang , Weiqi Luo , Xiaoqi Zhou

We characterize the quantum gate fidelity in a state-independent manner by giving an explicit expression for its variance. The method we provide can be extended to calculate all higher order moments of the gate fidelity. Using these results…

Quantum Physics · Physics 2012-04-30 Easwar Magesan , Robin Blume-Kohout , Joseph Emerson

Quantum teleportation should surpass maximum fidelity thresholds possible with local measurements and classical communications. Benchmarks have been established when states are drawn from a uniform distribution of qubits or coherent states…

Quantum Physics · Physics 2026-05-26 Tomáš Opatrný , Allison Brattley , Kunal K. Das

Transition Probability (fidelity) for pairs of density operators can be defined as "functor" in the hierarchy of "all" quantum systems and also within any quantum system. The introduction of "amplitudes" for density operators allows for a…

Quantum Physics · Physics 2016-04-08 Armin Uhlmann

We describe and discuss a solid state proposal for quantum computation with mobile spin qubits in one-dimensional systems, based on recent advances in spintronics. Static electric fields are used to implement a universal set of quantum…

Mesoscale and Nanoscale Physics · Physics 2007-05-23 A. E. Popescu , R. Ionicioiu

As various quantum computing technologies continue to compete for quantum supremacy, several parameters have emerged as benchmarks for the quality of qubits. These include fidelity, coherence times, connectivity, and a few others. In this…

Quantum Physics · Physics 2020-03-04 Daniel Koch , Avery Torrance , David Kinghorn , Saahil Patel , Laura Wessing , Paul M. Alsing

Fidelity is the standard measure for quantifying the similarity between two quantum states. It is equal to the square of the minimum Bhattacharyya coefficient between the probability distributions induced by quantum measurements on the two…

Quantum Physics · Physics 2025-12-01 Datong Chen , Huangjun Zhu

Full counting statistics is a fundamentally new concept in quantum transport. After a review of basic statistics theory, we introduce the powerful Green's function approach to full counting statistics. To illustrate the concept we consider…

Mesoscale and Nanoscale Physics · Physics 2018-05-09 W. Belzig

Despite the significant progress in superconducting quantum computation over the past years, quantum state measurement still lags nearly an order of magnitude behind quantum gate operations in speed and fidelity. The main challenge is that…

In this paper we address the problem of optimal reconstruction of a quantum state from the result of a single measurement when the original quantum state is known to be a member of some specified set. A suitable figure of merit for this…

Quantum Physics · Physics 2007-05-23 Kieran Hunter , Erika Andersson , Claire R. Gilson , Stephen M. Barnett

We introduce Quantum Functional Information (QFI), a new metric to quantify the rarity and utility of quantum states and circuits. Unlike standard measures such as fidelity or entropy, QFI captures the balance between functionality and…

Quantum Physics · Physics 2025-09-16 Rodrigo Pasti , Jonas Krause

Quantum computing hardware has grown sufficiently complex that it often can no longer be simulated by classical computers, but its computational power remains limited by errors. These errors corrupt the results of quantum algorithms, and it…

Fidelity is crucial for characterizing transformations of quantum states under various quantum channels, which can be served as a fundamental tool in resource theories. Firstly, we define an $\alpha$-$z$-fidelity as a significant quantity…

Quantum Physics · Physics 2025-07-08 Xiaojing Yan , Xiao Sun , Mingming Du , Jiashan Tang

We prove that a quantum circuit together with measurement apparatuses and EPR sources can be fully verified without any reference to some other trusted set of quantum devices. Our main assumption is that the physical system we are working…

Quantum Physics · Physics 2007-05-23 Frederic Magniez , Dominic Mayers , Michele Mosca , Harold Ollivier

We derive several bounds on fidelity between quantum states. In particular we show that fidelity is bounded from above by a simple to compute quantity we call super--fidelity. It is analogous to another quantity called sub--fidelity. For…

Quantum Physics · Physics 2008-11-19 J. A. Miszczak , Z. Puchała , P. Horodecki , A. Uhlmann , K. Życzkowski

We present a quantum algorithm to transform the cardinality of a set of charged particles flowing along a quantum wire into a binary number. The setup performing this task (for at most N particles) involves log_2 N quantum bits serving as…

Mesoscale and Nanoscale Physics · Physics 2015-05-13 G. B. Lesovik , M. V. Suslov , G. Blatter

We apply the fidelity metric approach to analyze two recently introduced models that exhibit a quantum phase transition to a topologically ordered phase. These quantum models have a known connection to classical statistical mechanical…

Quantum Physics · Physics 2008-07-03 Damian F. Abasto , Alioscia Hamma , Paolo Zanardi

We present a comprehensive analysis of fidelity decay and error accumulation in faulty quantum circuit models. Our work devises an analytical bound for the average fidelity between desired and faulty output states, accounting for errors…

When applied to different input states, an imperfect quantum operation yields output states with varying fidelities, defined as the absolute square of their overlap with the desired states. We present an expression for the distribution of…

Quantum Physics · Physics 2009-02-26 Line Hjortshoj Pedersen , Niels Martin Moller , Klaus Molmer

Quantum technology has been rapidly growing due to its potential revolutionary applications. In particular, superconducting qubits provide a strong light-matter interaction as required for quantum computation and in principle can be scaled…

Quantum Physics · Physics 2019-04-23 Mahdi Naghiloo