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Building on recent advances in quantum algorithms which measure and reuse qubits and in efficient classical simulation leveraging projective measurements, we extend these frameworks to real-time dynamics of quantum many-body systems…

Quantum Physics · Physics 2025-12-08 Bo Xiao , Benedikt Kloss , E. Miles Stoudenmire

In an ideal quantum measurement, the wave function of a quantum system collapses to an eigenstate of the measured observable, and the corresponding eigenvalue determines the measurement outcome. If the observable commutes with the system…

Quantum Physics · Physics 2020-02-13 Dayou Yang , Andrey Grankin , Lukas M. Sieberer , Denis V. Vasilyev , Peter Zoller

In quantum systems, the measurement of operators and the measurement of the quantum states of the system are very challenging tasks. In this Letter, we propose a method to obtain the average value of one operator in a certain state by…

There is a fundamental limit to what is knowable about atomic and molecular scale systems. This fuzziness is not always due to the act of measurement. Other contributing factors include system parameter uncertainty, functional uncertainty…

Quantum Physics · Physics 2022-10-31 Randa Herzallah , Abdessamad Belfakir

Achieving ultimate bounds in estimation processes is the main objective of quantum metrology. In this context, several problems require measurement of multiple parameters by employing only a limited amount of resources. To this end,…

Reconstructing the state of a complex quantum system represents a pivotal task for all quantum information applications, both for characterization purposes and for verification of quantum protocols. Recent technological developments have…

As they can travel long distances, free space optical quantum states are good candidates for carrying information in quantum information technology protocols. These states, however, are often complex to produce and require protocols whose…

Optics · Physics 2014-12-08 Jean Etesse , Bhaskar Kanseri , Rosa Tualle-Brouri

Quantum error correction is crucial for scalable quantum information processing applications. Traditional discrete-variable quantum codes that use multiple two-level systems to encode logical information can be hardware-intensive. An…

Quantum Physics · Physics 2024-06-12 Lucas Berent , Timo Hillmann , Jens Eisert , Robert Wille , Joschka Roffe

Characterization of quantum processes is a preliminary step necessary in the development of quantum technology. The conventional method uses standard quantum process tomography, which requires $d^2$ input states and $d^4$ quantum…

Quantum Physics · Physics 2020-02-26 Zhibo Hou , Jun-Feng Tang , Christopher Ferrie , Guo-Yong Xiang , Chuan-Feng Li , Guang-Can Guo

The origin of non-classical correlations is difficult to identify since the uncertainty principle requires that information obtained about one observable invariably results in the disturbance of any other non-commuting observable. Here,…

Quantum Physics · Physics 2014-07-01 Holger F. Hofmann

The standard quantum formalism introduced at the undergraduate level treats measurement as an instantaneous collapse. In reality however, no physical process can occur over a truly infinitesimal time interval. A more subtle investigation of…

Quantum Physics · Physics 2020-04-22 Leigh S. Martin

Quantum enhanced sensing provides a powerful tool for the precise measurement of physical parameters that is applicable in many areas of science and technology. The achievable gain in sensitivity is largely limited by the influence of noise…

Quantum Physics · Physics 2016-12-07 Yu Liu , Zijun Shu , Martin B. Plenio , Jianming Cai

Analog Quantum Simulators offer a route to exploring strongly correlated many-body dynamics beyond classical computation, but their predictive power remains limited by the absence of quantitative error estimation. Establishing rigorous…

Quantum trajectories describe the stochastic evolution of an open quantum system conditioned on continuous monitoring of its output, such as by an ideal photodetector. In practice an experimenter has access to an output filtered through…

Quantum Physics · Physics 2016-09-08 P. Warszawski , H. M. Wiseman

We present an algorithm that exploits quantum parallelism to simulate randomness in a quantum system. In our scheme, all possible realizations of the random parameters are encoded quantum mechanically in a superposition state of an…

Other Condensed Matter · Physics 2009-11-11 B. Paredes , F. Verstraete , J. I. Cirac

Extracting information from quantum devices has long been a crucial problem in the field of quantum mechanics. By performing elaborate measurements, quantum state tomography, an important and fundamental tool in quantum science and…

Quantum Physics · Physics 2022-06-24 Yu Wang , Keren Li

Quantum sensing promises measurement precision beyond classical limits, but its practical realization is often hindered by decoherence and the challenges of generating and stabilizing entanglement in large-scale systems. Here, we…

One of the most promising applications of quantum computing is simulating quantum many-body systems. However, there is still a need for methods to efficiently investigate these systems in a native way, capturing their full complexity. Here,…

Quantum Physics · Physics 2022-01-07 Korbinian Kottmann , Friederike Metz , Joana Fraxanet , Niccolo Baldelli

Quantum learning encounters fundamental challenges when estimating non-linear properties, owing to the inherent linearity of quantum mechanics. Although recent advances in single-copy randomized measurement protocols have achieved optimal…

Quantum Physics · Physics 2026-03-30 Zhenyu Du , Yifan Tang , Andreas Elben , Ingo Roth , Jens Eisert , Zhenhuan Liu

Adaptive filtering is a powerful class of control theoretic concepts useful in extracting information from noisy data sets or performing forward prediction in time for a dynamic system. The broad utilization of the associated algorithms…

Quantum Physics · Physics 2021-07-21 Riddhi S. Gupta , Michael J. Biercuk