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We present an instance of a task of minimum-error discrimination of two qubit-qubit quantum channels for which a sequential strategy outperforms any parallel strategy. We then establish two new classes of strategies for channel…

Quantum Physics · Physics 2021-11-24 Jessica Bavaresco , Mio Murao , Marco Túlio Quintino

Simultaneous estimation of multiple parameters is required in many practical applications. A lower bound on the variance of simultaneous estimation is given by the quantum Fisher information matrix. This lower bound is, however, not…

Quantum Physics · Physics 2020-04-22 Shingo Kukita

We analyze a discrimination problem of a single-qubit unitary gate with two candidates, where the candidates are not provided with their classical description, but their quantum sample is. More precisely, there are three unitary quantum…

Quantum Physics · Physics 2021-08-26 Akihito Soeda , Atsushi Shimbo , Mio Murao

Tasks involving black boxes appear frequently in quantum computer science. An example that has been deeply studied is quantum channel discrimination. In this work, we study the discrimination between two quantum unitary channels in the…

Quantum Physics · Physics 2025-05-26 Adam Bílek , Jan Hlisnikovský , Tomáš Bezděk , Ryszard Kukulski , Paulina Lewandowska

We study equivalence determination of unitary operations, a task analogous to quantum state discrimination. The candidate states are replaced by unitary operations given as a quantum sample, i.e., a black-box device implementing a candidate…

Quantum Physics · Physics 2018-04-02 Atsushi Shimbo , Akihito Soeda , Mio Murao

We determine a fundamental upper bound on the performance of any adaptive protocol for discrimination or estimation of a channel which has an unknown parameter encoded in the state of its environment. Since our approach relies on the…

Quantum Physics · Physics 2016-11-29 Masahiro Takeoka , Mark M. Wilde

In this work, we study Bayesian quantum parameter estimation given a finite number of uses of the process encoding one or more unknown physical quantities. For multiple uses, it is conventional to classify quantum metrological protocols as…

Quantum Physics · Physics 2026-02-11 Erik L. André , Jessica Bavaresco , Mohammad Mehboudi

We investigate the performance of discrimination strategy in the comparison task of known quantum states. In the discrimination strategy, one infers whether or not two quantum systems are in the same state on the basis of the outcomes of…

Quantum Physics · Physics 2018-05-30 A. Hayashi , T. Hashimoto , M. Horibe

Consider a collection of competing machine learning algorithms. Given their performance on a benchmark of datasets, we would like to identify the best performing algorithm. Specifically, which algorithm is most likely to rank highest on a…

Machine Learning · Computer Science 2025-08-08 Amichai Painsky

Model-based sequential approaches to discrete "black-box" optimization, including Bayesian optimization techniques, often access the same points multiple times for a given objective function in interest, resulting in many steps to find the…

Machine Learning · Computer Science 2023-12-29 Keisuke Morita , Yoshihiko Nishikawa , Masayuki Ohzeki

We consider two different optimized measurement strategies for the discrimination of nonorthogonal quantum states. The first is conclusive discrimination with a minimum probability of inferring an erroneous result, and the second is…

Quantum Physics · Physics 2009-11-10 Ulrike Herzog , Janos A. Bergou

The inevitable accumulation of errors in near-future quantum devices represents a key obstacle in delivering practical quantum advantages, motivating the development of various quantum error-mitigation methods. Here, we derive fundamental…

Quantum Physics · Physics 2022-09-23 Ryuji Takagi , Suguru Endo , Shintaro Minagawa , Mile Gu

In this work, we consider optimal state discrimination for a quantum system that interacts with an environment, i.e., states evolve under a quantum channel. We show the conditions on a quantum channel and an ensemble of states such that a…

Quantum Physics · Physics 2019-06-12 Spiros Kechrimparis , Tanmay Singal , Chahan M. Kropf , Joonwoo Bae

This expository article gives an overview of the theory of hypothesis testing of quantum states in finite dimensional Hilbert spaces. Optimal measurement strategy for testing binary quantum hypotheses, which result in minimum error…

Quantum Physics · Physics 2018-03-14 J. Prabhu Tej , Syed Raunaq Ahmed , A. R. Usha Devi , A. K. Rajagopal

A universal programmable quantum processor uses program quantum states to apply an arbitrary quantum channel to an input state. We generalize the concept of a finite-dimensional programmable quantum processor to infinite dimension assuming…

Quantum Physics · Physics 2021-07-15 Martina Gschwendtner , Andreas Winter

In this paper, we compute the tightest possible bounds on the probability that the optimal value of a combinatorial optimization problem in maximization form with a random objective exceeds a given number, assuming only knowledge of the…

Optimization and Control · Mathematics 2022-11-24 Divya Padmanabhan , Selin Damla Ahipasaoglu , Arjun Ramachandra , Karthik Natarajan

We discuss the problem of designing an unambiguous programmable discriminator for mixed quantum states. We prove that there does not exist such a universal unambiguous programmable discriminator for mixed quantum states that has two program…

Quantum Physics · Physics 2007-05-23 Hongfeng Gan , Daowen Qiu

In this work, a new upper bound for average error probability of a two-user discrete memoryless (DM) multiple-access channel (MAC) is derived. This bound can be universally obtained for all discrete memoryless MACs with given input and…

Information Theory · Computer Science 2009-01-09 Ali Nazari , Achilleas Anastasopoulos , S. Sandeep Pradhan

We derive general discrimination of quantum states chosen from a certain set, given initial $M$ copies of each state, and obtain the matrix inequality, which describe the bound between the maximum probability of correctly determining and…

Quantum Physics · Physics 2009-10-31 Chuan-Wei Zhang , Chuan-Feng Li , Guang-Can Guo

The problem of sequentially maximizing the expectation of a function seeks to maximize the expected value of a function of interest without having direct control on its features. Instead, the distribution of such features depends on a given…

Machine Learning · Statistics 2022-10-26 Diego Martinez-Taboada , Dino Sejdinovic