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We present an iterative method to solve the multipartite quantum state estimation problem. We demonstrate convergence for any informationally complete set of generalized quantum measurements in every finite dimension. Our method exhibits…

Quantum Physics · Physics 2022-03-21 Daniel Uzcategui Contreras , Gabriel Senno , Dardo Goyeneche

Current techniques in quantum process tomography typically return a single point estimate of an unknown process based on a finite albeit large amount of measurement data. Due to statistical fluctuations, however, other processes close to…

Quantum Physics · Physics 2019-05-15 Le Phuc Thinh , Philippe Faist , Jonas Helsen , David Elkouss , Stephanie Wehner

Quantum metrology holds the promise of an early practical application of quantum technologies, in which measurements of physical quantities can be made with much greater precision than what is achievable with classical technologies. In this…

Quantum Physics · Physics 2021-01-27 Jasminder S. Sidhu , Pieter Kok

The initialization of a quantum system into a certain state is a crucial aspect of quantum information science. While a variety of measurement strategies have been developed to characterize how well the system is initialized, for a given…

Consider the task of verifying that a given quantum device, designed to produce a particular entangled state, does indeed produce that state. One natural approach would be to characterise the output state by quantum state tomography; or…

Quantum Physics · Physics 2018-04-26 Sam Pallister , Noah Linden , Ashley Montanaro

Continuous U(1) gauge symmetry, which guarantees the conservation of the total excitations in linear bosonic systems, will be broken when it comes to the strong-coupling regime where the rotation wave approximation (RWA) fails. Here we…

Quantum Physics · Physics 2025-01-03 Yilun Xu , Daoquan Zhu , Feng-Xiao Sun , Qiongyi He , Wei Zhang

We discuss a recently developed formalism which describes the quantum evolution of a solid-state qubit due to its continuous measurement. In contrast to the conventional ensemble-averaged formalism, it takes into account the measurement…

Mesoscale and Nanoscale Physics · Physics 2007-05-23 Alexander N. Korotkov

Quantum tomography is one of the major challenges of large-scale quantum information research due to the exponential time complexity. In this work, we develop and apply a Bayesian state estimation method to experimentally demonstrate…

Quantum Physics · Physics 2025-11-13 Yang Zhengning , Shihao Ru , Lianzhen Cao , Nikolay Zheludev , Weibo Gao

The theory of continuous quantum measurement allows to reconstruct the state $\rho_t$ of a system from a continuous stochastic measurement record $I_t$. However, this truly continuous-time signal $I_t$ is never available in practice. In…

Quantum Physics · Physics 2025-05-28 Pierre Guilmin , Pierre Rouchon , Antoine Tilloy

Quantum voting protocols aim to offer ballot secrecy and publicly verifiable tallies using physical guarantees from quantum mechanics, rather than relying solely on computational hardness. This article surveys whether such quantum voting…

Quantum Physics · Physics 2026-01-27 Nitin Jha , Abhishek Parakh

Several Bayesian estimation based heuristics have been developed to perform quantum state tomography (QST). Their ability to quantify uncertainties using region estimators and include a priori knowledge of the experimentalists makes this…

Quantum Physics · Physics 2021-09-16 Syed Muhammad Kazim , Ahmad Farooq , Junaid ur Rehman , Hyundong Shin

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

The advantage of quantum protocols lies in the inherent properties of the shared quantum states. These states are sometimes provided by sources that are not trusted, and therefore need to be verified. Finding secure and efficient quantum…

Quantum Physics · Physics 2025-12-16 Fabian Wiesner , Ziad Chaoui , Diana Kessler , Anna Pappa , Martti Karvonen

Fidelity estimation for entangled states constitutes an essential building block for quality control and error detection in quantum networks. Nonetheless, quantum networks often encounter heterogeneous and correlated noise, leading to…

Quantum Physics · Physics 2024-11-18 Liangzhong Ruan , Bas Dirkse

Quantum state tomography is the fundamental physical task of learning a complete classical description of an unknown state of a quantum system given coherent access to many identical samples of it. The complexity of this task is commonly…

Quantum Physics · Physics 2026-05-25 Yanglin Hu , Enrique Cervero-Martín , Elias Theil , Laura Mančinska , Marco Tomamichel

The efficiency of quantum state tomography is discussed from the point of view of quantum parameter estimation theory, in which the trace of the weighted covariance is to be minimized. It is shown that tomography is optimal only when a…

Quantum Physics · Physics 2015-03-17 Koichi Yamagata

We present a deterministic approach based on continuous measurement and real-time quantum feedback control to prepare arbitrary photon number states of a cavity mode. The procedure passively monitors the number state actually achieved in…

Quantum Physics · Physics 2009-11-13 JM Geremia

Quantum state tomography (QST) remains the gold standard for benchmarking and verification of near-term quantum devices. While QST for a generic quantum many-body state requires an exponentially large amount of resources, most physical…

Quantum Physics · Physics 2024-08-15 Casey Jameson , Zhen Qin , Alireza Goldar , Michael B. Wakin , Zhihui Zhu , Zhexuan Gong

Quantum state tomography is an integral part of quantum computation and offers the starting point for the validation of various quantum devices. One of the central tasks in the field of state tomography is to reconstruct with high fidelity,…

Quantum Physics · Physics 2022-12-21 Rishabh Gupta , Manas Sajjan , Raphael D. Levine , Sabre Kais

Continuous-variable quantum key distribution (CV-QKD) enables two remote parties to establish information-theoretically secure keys and offers high practical feasibility due to its compatibility with mature coherent optical communication…

Quantum Physics · Physics 2025-12-18 Yanhao Sun , Jiayu Ma , Xiangyu Wang , Song Yu , Ziyang Chen , Hong Guo