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Quantum state smoothing is a technique to estimate an unknown true state of an open quantum system based on partial measurement information both prior and posterior to the time of interest. In this paper, we show that the smoothed quantum…

Quantum Physics · Physics 2021-09-24 Kiarn T. Laverick , Ivonne Guevara , Howard M. Wiseman

In the area of statistical planning, there is a large body of theoretical knowledge and computational experience concerning so-called optimal approximate designs of experiments. However, for an approximate design to be executed in practice,…

Computation · Statistics 2019-03-25 Lenka Filová , Radoslav Harman

We experimentally demonstrate a two-particle collective measurement proposed as the optimal solution to a quantum state estimation game. Our results suggest that, in practice, the collective measurement strategy is at least as good as the…

Quantum Physics · Physics 2026-02-05 Arman Mansouri , Kyle M. Jordan , Raphael A. Abrahao , Jeff S. Lundeen

The optimal quantum measurements for estimating different unknown parameters in a parameterized quantum state are usually incompatible with each other. Traditional approaches to addressing the measurement incompatibility issue, such as the…

Quantum Physics · Physics 2026-02-03 Sisi Zhou , Senrui Chen

We propose a scheme for unambiguous state comparison (USC) of two unknown squeezed vacuum states of an electromagnetic field. Our setup is based on linear optical elements and photon-number detectors, and achieves optimal USC in an ideal…

Quantum Physics · Physics 2015-05-20 Stefano Olivares , Michal Sedlak , Peter Rapcan , Matteo G. A. Paris , Vladimir Buzek

In this paper, we introduce stochastic simulated quantum annealing (SSQA) for large-scale combinatorial optimization problems. SSQA is designed based on stochastic computing and quantum Monte Carlo, which can simulate quantum annealing (QA)…

Quantum Physics · Physics 2024-07-25 Naoya Onizawa , Ryoma Sasaki , Duckgyu Shin , Warren J. Gross , Takahiro Hanyu

We investigate how to determine whether the states of a set of quantum systems are identical or not. This paper treats both error-free comparison, and comparison where errors in the result are allowed. Error-free comparison means that we…

Quantum Physics · Physics 2015-06-26 Igor Jex , Erika Andersson , Anthony Chefles

We discuss the accuracy of the estimation of the $n$ identical unknown actions of $\SU(2)$ by using entanglement. This problem has a similar structure with the phase estimation problem, which was discussed by Bu\v{z}ek, Derka, and…

Quantum Physics · Physics 2009-11-10 Masahito Hayashi

A method to compute the optimal success probability of discrimination of N arbitrary quantum states is presented, based on the decomposition of any N-outcome measurement into sequences of nested two-outcome ones. In this way the…

Quantum Physics · Physics 2017-04-12 Matteo Rosati , Giacomo De Palma , Andrea Mari , Vittorio Giovannetti

We derive optimal rates of convergence in the supremum norm for estimating the H\"older-smooth mean function of a stochastic process which is repeatedly and discretely observed with additional errors at fixed, multivariate, synchronous…

Statistics Theory · Mathematics 2024-05-09 Max Berger , Philipp Hermann , Hajo Holzmann

Quantum state estimation is important for various quantum information processes, including quantum communications, computation, and metrology, which require the characterization of quantum states for evaluation and optimization. We present…

Quantum Physics · Physics 2026-04-15 C. Vargas , L. Pereira , A. Delgado

Quantum state tomography (QST) is one of the fundamental problems in quantum information. Among various metrics, sample complexity is widely used to evaluate QST algorithms. While multi-copy measurements are known to achieve optimal sample…

Quantum Physics · Physics 2025-09-17 Gyungmin Cho , Dohun Kim

Unitary $t$-designs are the bread and butter of quantum information theory and beyond. An important issue in practice is that of efficiently constructing good approximations of such unitary $t$-designs. Building on results by Aubrun (Comm.…

Quantum Physics · Physics 2020-09-02 Cécilia Lancien , Christian Majenz

The efficient and reliable characterization of quantum states plays a vital role in most, if not all, quantum information processing tasks. In this work, we present a universally optimal protocol for verifying entangled states by employing…

Quantum Physics · Physics 2021-03-08 Ye-Chao Liu , Jiangwei Shang , Rui Han , Xiangdong Zhang

This work investigates variational compilation methods for simulating quantum systems with internal SU(2) symmetry. The central component of the research is the application of the Dynamic Mode Decomposition (DMD) method to extrapolate…

Quantum Physics · Physics 2025-06-26 Oleksa Hryniv

We derive a tight upper bound for the fidelity of a universal N to M qubit cloner, valid for any M \geq N, where the output of the cloner is required to be supported on the symmetric subspace. Our proof is based on the concatenation of two…

Quantum Physics · Physics 2009-01-23 D. Bruss , A. Ekert , C. Macchiavello

We present an experimentally feasible and efficient method for detecting entangled states with measurements that extend naturally to a tomographically complete set. Our detection criterion is based on measurements from subsets of a quantum…

Quantum Physics · Physics 2019-01-30 Joonwoo Bae , Beatrix C. Hiesmayr , Daniel McNulty

We consider the problem of designing an optimal quantum detector with a fixed rate of inconclusive results that maximizes the probability of correct detection, when distinguishing between a collection of mixed quantum states. We develop a…

Quantum Physics · Physics 2009-11-07 Yonina C. Eldar

The focus of this paper is on trend estimation for a general state-space model $Y_t=\mu_t+\varepsilon_t$, where the $d$th difference of the trend $\{\mu_t\}$ is assumed to be i.i.d., and the error sequence $\{\varepsilon_t\}$ is assumed to…

Statistics Theory · Mathematics 2009-11-19 Prabir Burman , Robert H. Shumway

We construct optimal measurements, achieving the ultimate precision predicted by quantum theory, for the simultaneous estimation of centroid, separation, and relative intensities of two incoherent point sources using a linear optical…

Quantum Physics · Physics 2018-07-04 J. Rehacek , Z. Hradil , D. Koutny , J. Grover , A. Krzic , L. L. Sanchez-Soto