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Noisy unsharp measurements incorporated in quantum information protocols may hinder performance, reducing the quantum advantage. However, we show that, unlike projective measurements which completely destroy quantum correlations between…

Quantum Physics · Physics 2025-07-01 Sudipta Mondal , Pritam Halder , Amit Kumar Pal , Aditi Sen De

Precision metrology underpins scientific and technological advancements. Quantum metrology offers a pathway to surpass classical sensing limits by leveraging quantum states and measurement strategies. However, measuring multiple…

The indeterminism of quantum mechanics generally permits the independent specification of both an initial and a final condition on the state. Quantum pre-and-post-selection of states opens up a new, experimentally testable, sector of…

Quantum Physics · Physics 2015-06-17 Paul Davies

The problem of feedback control of quantum systems by means of weak measurements is investigated in detail. When weak measurements are made on a set of identical quantum systems, the single-system density matrix can be determined to a high…

Quantum Physics · Physics 2009-10-31 Seth Lloyd , Jean-Jacques E. Slotine

Quantum metrology promises high-precision measurements of classical parameters with far reaching implications for science and technology. So far, research has concentrated almost exclusively on quantum-enhancements in integrable systems,…

Quantum Physics · Physics 2018-04-16 Lukas J. Fiderer , Daniel Braun

Sensors that harness exclusively quantum phenomena (such as entanglement) can achieve superior performance compared to those employing only classical principles. Recently, a technique based on postselected, weakly-performed measurements has…

Quantum Physics · Physics 2013-01-18 George C. Knee , G. Andrew D. Briggs , Simon C. Benjamin , Erik M. Gauger

Quantum computation has been growing rapidly in both theory and experiments. In particular, quantum computing devices with a large number of qubits have been developed by IBM, Google, IonQ, and others. The current quantum computing devices…

Quantum Physics · Physics 2021-02-10 Rishabh Gupta , Rongxin Xia , Raphael D. Levine , Sabre Kais

Quantum systems are promising candidates for sensing of weak signals as they can provide unrivaled performance when estimating parameters of external fields. However, when trying to detect weak signals that are hidden by background noise,…

Quantum Physics · Physics 2021-07-19 Paraj Titum , Kevin M. Schultz , Alireza Seif , Gregory D. Quiroz , B. D. Clader

In quantum information processing it may be possible to have efficient computation and secure communication beyond the limitations of classical systems. In a fundamental point of view, however, evolution of quantum systems by the laws of…

Quantum Physics · Physics 2017-09-21 Joonwoo Bae

Combining quantum sensing with quantum computing can lead to quantum computational sensors that are able to more efficiently extract task-specific information from physical signals than is possible otherwise. Early examples of quantum…

Quantum Physics · Physics 2025-07-22 Saeed A. Khan , Sridhar Prabhu , Logan G. Wright , Peter L. McMahon

Adaptive measurements were recently shown to significantly improve the performance of quantum state tomography. Utilizing information about the system for the on-line choice of optimal measurements allows to reach the ultimate bounds of…

Quantum mechanics is potentially advantageous for certain information-processing tasks, but its probabilistic nature and requirement of measurement back action often limit the precision of conventional classical information-processing…

Quantum Physics · Physics 2012-10-05 Mankei Tsang , Carlton M. Caves

We investigate the estimation technique called quantum state smoothing introduced by Guevara and Wiseman [Phys.~Rev.~Lett.~{\bf 115}, 180407 (2015)], which offers a valid quantum state estimate for a partially monitored system, conditioned…

Quantum Physics · Physics 2020-04-23 Areeya Chantasri , Ivonne Guevara , Howard M. Wiseman

The accurate characterization of quantum systems is essential for the advancement of quantum technologies. In particular, certifying convex functions of quantum states plays a central role in many applications. We present a certification…

Quantum Physics · Physics 2026-01-26 Leonardo Zambrano , Teodor Parella-Dilmé , Antonio Acín , Donato Farina

Small, controllable quantum systems, known as quantum probes, have been proposed to estimate various parameters characterizing complex systems such as the environments of quantum systems. These probes, prepared in some initial state, are…

Quantum Physics · Physics 2021-07-21 Hamza Ather , Adam Zaman Chaudhry

The precision and sensitivity achievable in quantum metrology are often compromised by the presence of noise. While quantum error correction has emerged as a promising strategy, it is ineffective in addressing noise that is…

Quantum Physics · Physics 2026-05-25 Xiaodie Lin , Linxuan Li , Haidong Yuan

We consider the problem of correcting the errors incurred from sending classical or quantum information through a noisy quantum environment by schemes using classical information obtained from a measurement on the environment. We give a…

Quantum Physics · Physics 2015-06-26 M. Gregoratti , R. F. Werner

Mechanical systems are ideal candidates for studying quantumbehavior of macroscopic objects. To this end, a mechanical resonator has to be cooled to its ground state and its position has to be measured with great accuracy. Currently,…

Mesoscale and Nanoscale Physics · Physics 2012-03-16 Menno Poot , Herre S. J. van der Zant

In this paper we consider the purification of a quantum state using the information obtained from a continuous measurement record, where the classical measurement record is digitized to a single bit per measurement after the measurements…

Quantum Physics · Physics 2012-01-05 Jason F. Ralph , Neil P. Oxtoby

Quantum information processing offers promising advances for a wide range of fields and applications, provided that we can efficiently assess the performance of the control applied in candidate systems. That is, we must be able to determine…

Quantum Physics · Physics 2015-01-26 Christopher Granade , Christopher Ferrie , D. G. Cory