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Protocols for quantum measurement are an essential part of quantum computing. Measurements are no longer confined to the final step of computation but are increasingly embedded within quantum circuits as integral components of…

Quantum Physics · Physics 2025-11-07 Michal Krejčí , Lucie Krejčí , Ijaz Ahamed Mohammad , Martin Plesch , Martin Friák

We realize a non-invasive electrometer based on state engineering in a Rydberg hydrogenic manifold. A quantum interference process involving states with very different dipoles measures directly the time correlation of a stochastic electric…

Quantum Physics · Physics 2018-05-18 E. K. Dietsche , A. Larrouy , J. M. Raimond , M. Brune , S. Gleyzes

Achieving fault-tolerant quantum computation (FTQC) demands simultaneous progress in physical qubit performance and quantum error correction (QEC). This work reviews and benchmarks experimental advancements towards FTQC across leading…

Quantum Physics · Physics 2025-07-08 François-Marie Le Régent

Fast, high-fidelity measurement is a key ingredient for quantum error correction. Conventional approaches to the measurement of superconducting qubits, involving linear amplification of a microwave probe tone followed by heterodyne…

Due to the technical difficulty of building large quantum computers, it is important to be able to estimate how faithful a given implementation is to an ideal quantum computer. The common approach of completely characterizing the…

Quantum Physics · Physics 2012-08-20 Osama Moussa , Marcus P. da Silva , Colm A. Ryan , Raymond Laflamme

Quantum metrology uses small changes in the output probabilities of a quantum measurement to estimate the magnitude of a weak interaction with the system. The sensitivity of this procedure depends on the relation between the input state,…

Quantum Physics · Physics 2011-03-02 Holger F. Hofmann

Von Neumann's classic "multiplexing" method is unique in achieving high-threshold fault-tolerant classical computation (FTCC), but has several significant barriers to implementation: i) the extremely complex circuits required by randomized…

Quantum Physics · Physics 2017-07-25 Benjamin Cruikshank , Kurt Jacobs

The power of quantum sensing rests on its ultimate precision limit, quantified by the quantum Cramer-Rao bound (QCRB), which can surpass classical bounds. In multi-parameter estimation, the QCRB is not always saturated as the quantum nature…

Quantum Physics · Physics 2024-05-24 Changhao Li , Mo Chen , Paola Cappellaro

Mistrustful quantum cryptographic protocols encode information in incompatible observables, so that any attempt by a dishonest party to access multiple pieces of information necessarily involves a tradeoff. A natural class of such…

Quantum Physics · Physics 2026-03-31 Chen-Xun Weng , Minglong Qin , Yanglin Hu , Marco Tomamichel

The major resolution-limiting factor in cryoelectron microscopy of unstained biological specimens is radiation damage by the very electrons that are used to probe the specimen structure. To address this problem, an electron microscopy…

Quantum Physics · Physics 2015-06-18 Hiroshi Okamoto

Quantum bits, or qubits, are the fundamental building blocks of present quantum computers. Hence, it is important to be able to characterize the state of a qubit as accurately as possible. By evaluating the qubit characterization problem…

Quantum Physics · Physics 2024-02-27 Bacui Li , Lorcan O. Conlon , Ping Koy Lam , Syed M. Assad

We discuss a quantum-metrology protocol designed to estimate a physical parameter in a Bose-Einstein condensate of N atoms, and we show that the measurement uncertainty can decrease faster than 1/N. The 1/N scaling is usually thought to be…

How well can multiple incompatible observables be implemented by a single measurement? This is a fundamental problem in quantum mechanics with wide implications for the performance optimization of numerous tasks in quantum information…

Quantum Physics · Physics 2024-10-10 Hongzhen Chen , Lingna Wang , Haidong Yuan

Traditional quantum metrology assesses precision using the figures of merit of continuous-valued parameter estimation. Recently, quantum digital estimation was introduced: it evaluates the performance information-theoretically by…

Quantum metrology aims to enhance measurement precision beyond the classical limit by leveraging quantum resources. Unlike multi-parameter dynamic quantum metrology, many questions regarding multiparameter quantum metrology at thermal…

Quantum Physics · Physics 2026-05-20 Zhu Cao

Measurements on near-term quantum processors are inevitably subject to hardware imperfections that lead to readout errors. Mitigation of such unavoidable errors is crucial to better explore and extend the power of near-term quantum…

Quantum Physics · Physics 2023-09-19 Kun Wang , Yu-Ao Chen , Xin Wang

In this paper, we study the quantum decoherence induced by accumulation of electron tunnelings during the quantum measurement of a charge qubit. The charge qubit is a single electron confined in coupled quantum dots. The measurement of the…

Mesoscale and Nanoscale Physics · Physics 2009-11-11 Ming-Tsung Lee , Wei-Min Zhang

The entropic uncertainty relation with quantum side information (EUR-QSI) from [Berta et al., Nat. Phys. 6, 659 (2010)] is a unifying principle relating two distinctive features of quantum mechanics: quantum uncertainty due to measurement…

Quantum Physics · Physics 2016-07-07 Mario Berta , Stephanie Wehner , Mark M. Wilde

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…

Recent development in quantum information sciences and technologies, especially building programmable quantum computers, provide us new opportunities to study fundamental aspects of quantum mechanics. We propose qubit models to emulate the…

Quantum Physics · Physics 2022-06-29 Meng-Jun Hu , Yanbei Chen , Yiqiu Ma , Xiang Li , Yubao Liu , Yong-Sheng Zhang , Haixing Miao