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Quantum phase transitions in Rydberg atom arrays present significant opportunities for studying many-body physics, yet distinguishing between different ordered phases without explicit order parameters remains challenging. We present a…

Quantum Physics · Physics 2025-10-28 Hemish Ahuja , Samradh Bhardwaj , Kirti Dhir , Roman Bagdasarian , Ziwoong Jang

Hybrid quantum-classical algorithms hold great promise for solving quantum control problems on near-term quantum computers. In this work, we employ the hybrid framework that integrates digital quantum simulation with classical optimization…

Quantum Physics · Physics 2025-07-01 Tangyou Huang , Jing-Jun Zhu , Zhong-Yi Ni

Improving the performance of quantum algorithms is a fundamental task to achieve quantum advantage. In many cases, extracting information from quantum systems poses an important challenge for practical implementations in real-world quantum…

Quantum Physics · Physics 2025-02-28 Leticia Bertuzzi , João P. Engster , Evandro C. R. da Rosa , Eduardo I. Duzzioni

We introduce a method that allows one to infer many properties of a quantum state -- including nonlinear functions such as R\'enyi entropies -- using only global control over the constituent degrees of freedom. In this protocol, the state…

Quantum Physics · Physics 2023-11-20 Max McGinley , Michele Fava

Recently, variational quantum metrology was proposed for Hamiltonians with multiplicative parameters, wherein the estimation precision can be optimized via variational circuits. However, systems with generic Hamiltonians still lack these…

Quantum Physics · Physics 2023-09-25 Le Bin Ho

Quantum algorithms for electronic-structure simulations are actively being developed, yet many hybrid quantum-classical approaches are bottlenecked by the measurement overhead associated with large molecular Hamiltonians. Here we introduce…

Quantum Physics · Physics 2026-03-10 Benjamin Mokhtar , Noboru Inoue , Takashi Tsuchimochi

Outcome probability estimation via classical methods is an important task for validating quantum computing devices. Outcome probabilities of any quantum circuit can be estimated using Monte Carlo sampling, where the amount of negativity…

Quantum Physics · Physics 2022-10-14 Nikolaos Koukoulekidis , Hyukjoon Kwon , Hyejung H. Jee , David Jennings , M. S. Kim

We introduce a class of hybrid quantum circuits, with random unitaries and projective measurements, which host long-range order in the area law entanglement phase of the steady state. Our primary example is circuits with unitaries…

Statistical Mechanics · Physics 2021-06-22 Shengqi Sang , Timothy H. Hsieh

Classical shadow estimation (CSE) is a powerful tool for learning the properties of quantum states and quantum processes. Here we consider the CSE task for quantum unitary channels. By querying an unknown unitary channel $\mathcal{U}$…

Quantum Physics · Physics 2025-12-30 Zihao Li , Changhao Yi , You Zhou , Huangjun Zhu

The accurate and reliable description of measurement devices is a central problem in both observing uniquely non-classical behaviors and realizing quantum technologies from powerful computing to precision metrology. To date quantum…

Quantum Physics · Physics 2020-01-30 Aonan Zhang , Jie Xie , Huichao Xu , Kaimin Zheng , Han Zhang , Yiu-Tung Poon , Vlatko Vedral , Lijian Zhang

Topological quantum computing promises intrinsic fault tolerance by encoding quantum information in non-Abelian anyons, where quantum gates are implemented via braiding. While braiding operations are robust against local perturbations, a…

Quantum Physics · Physics 2025-08-15 Themba Hodge , Philipp Frey , Stephan Rachel

Quantum measurements are slow, while classical processors are fast, yet existing hybrid protocols never exploit this asymmetry. In this work, we propose an alternative formulation of classical estimators as online algorithms that are…

Quantum Physics · Physics 2026-03-30 Marwa Marso , Sabrina Herbst , Jadwiga Wilkens , Vincenzo De Maio , Ivona Brandic , Richard Kueng

When one performs a continuous measurement, whether on a classical or quantum system, the measurement provides a certain average rate at which one becomes certain about the state of the system. For a quantum system this is an average rate…

Quantum Physics · Physics 2009-11-10 Kurt Jacobs

How classical chaos emerges from the underlying quantum world is a fundamental problem in physics. The origin of this question is in the correspondence principle. Classical chaos arises due to non-linear dynamics, whereas quantum mechanics,…

Quantum Physics · Physics 2024-02-02 Sreeram PG

We propose a hybrid quantum approach to threshold and binarize a grayscale image through unsharp measurements (UM) relying on image histogram. Generally, the histograms are characterized by multiple overlapping normal distributions…

Quantum Physics · Physics 2024-01-02 Ayan Barui , Mayukha Pal , Prasanta K. Panigrahi

Unsharp measurements are increasingly important for foundational insights in quantum theory and quantum information applications. Here, we report an experimental implementation of unsharp qubit measurements in a sequential communication…

Quantum trajectories are Markov chains modeling quantum systems subjected to repeated indirect measurements. Their stationary regime depends on what observables are measured on the probes used to indirectly measure the system. In this…

Mathematical Physics · Physics 2026-03-31 Tristan Benoist , Sascha Lill , Cornelia Vogel

In quantum computing, the indirect measurement of unitary operators such as the Hadamard test plays a significant role in many algorithms. However, in certain cases, the indirect measurement can be reduced to the direct measurement, where a…

Quantum Physics · Physics 2019-08-14 Kosuke Mitarai , Keisuke Fujii

We present a hybrid model of the unitary-evolution-based quantum computation model and the measurement-based quantum computation model. In the hybrid model part of a quantum circuit is simulated by unitary evolution and the rest by…

Quantum Physics · Physics 2011-05-19 Arun Sehrawat , Daniel Zemann , Berthold-Georg Englert

We present a method for optimizing quantum control in experimental systems, using a subset of randomized benchmarking measurements to rapidly infer error. This is demonstrated to improve single- and two-qubit gates, minimize gate…