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Given a pure state vector |x> and a density matrix rho, the function p(x|rho)=<x|rho|x> defines a probability density on the space of pure states parameterised by density matrices. The associated Fisher-Rao information measure is used to…

Quantum Physics · Physics 2011-06-03 Dorje C. Brody

Quantum state discrimination depicts the general progress of extracting classical information from quantum systems. We show that quantum state discrimination can be realized in a device-independent scenario using tools of self-testing…

Quantum Physics · Physics 2024-01-25 Xinyu Qiu , Lin Chen

Discriminating between quantum states is a fundamental problem in quantum information protocols. The optimum approach saturates the Helstrom bound, which quantifies the unavoidable error probability of mistaking one state for another.…

Quantum Physics · Physics 2019-07-24 Shannon Ray , James Schneeloch , Christopher C. Tison , Paul M. Alsing

We establish a sharp quantum advantage in determining the parity (even/odd) of an unknown permutation applied to any number $n \ge 3$ of particles. Classically, this is impossible with fewer than $n$ labels, being that the success is…

Quantum state separation is a probabilistic map that transforms a given set of pure states into another set of more distinguishable ones. Here we investigate such a map acting onto uniparametric families of symmetric linearly dependent or…

Quantum Physics · Physics 2017-03-09 M. A. Solís-Prosser , A. Delgado , O. Jiménez , L. Neves

We find the allowed complex numbers associated with the inner product of N equally separated pure quantum states. The allowed areas on the unitary complex plane have the form of petals. A point inside the petal-shape represents a set of N…

Quantum Physics · Physics 2008-08-07 Luis Roa , Carla Hermann-Avigliano , Roberto Salazar , A. B. Klimov , B. Burgos , A. Delgado

What is the quantum state of the universe? Although there have been several interesting suggestions, the question remains open. In this paper, I consider a natural choice for the universal quantum state arising from the Past Hypothesis, a…

Quantum Physics · Physics 2019-01-25 Eddy Keming Chen

We consider a quantum walk where a detector repeatedly probes the system with fixed rate $1/\tau$ until the walker is detected. This is a quantum version of the first-passage problem. We focus on the total probability, $P_{\mathrm{det}}$,…

Quantum Physics · Physics 2020-10-28 Felix Thiel , Itay Mualem , Dror Meidan , Eli Barkai , David A. Kessler

A mixed quantum state is represented by a Hermitian positive semi-definite operator $\rho$ with unit trace. The positivity requirement is responsible for a highly nontrivial geometry of the set of quantum states. A known way to satisfy this…

Quantum Physics · Physics 2020-02-18 N. Il'in , E. Shpagina , F. Uskov , O. Lychkovskiy

This thesis investigates the entanglement of distinguishable and indistinguishable particles, introducing a new error model for Hardy's test, experimentally verified using superconducting qubits. We address challenges in implementing…

Quantum Physics · Physics 2025-03-12 Soumya Das

Starting from the famous Pauli problem on the possibility to associate quantum states with probabilities, the formulation of quantum mechanics in which quantum states are described by fair probability distributions (tomograms, i.e.…

Quantum Physics · Physics 2015-05-13 A. Ibort , V. I. Man'ko , G. Marmo , A. Simoni , F. Ventriglia

We relate the the distinguishability of quantum states with their robustness of the entanglement, where the robustness of any resource quantifies how tolerant it is to noise. In particular, we identify upper and lower bounds on the…

Quantum Physics · Physics 2025-12-24 Debarupa Saha , Kornikar Sen , Chirag Srivastava , Ujjwal Sen

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

Any rule for identifying a quantum system's state within a set of two non-orthogonal pure states by a single measurement is flawed. It has a non-zero probability of either yielding the wrong result or leaving the query undecided. This also…

Quantum Physics · Physics 2012-04-16 Gebhard Gruebl , Laurin Ostermann

We study the discrimination of N mixed quantum states in an optimal measurement that maximizes the probability of correct results while the probability of inconclusive results is fixed at a given value. After considering the discrimination…

Quantum Physics · Physics 2015-06-11 Ulrike Herzog

Quantum coherence is an exquisitely quantum phenomenon that depends on both probability amplitudes and relative phases. Standard coherence measures quantify superposition within density matrices but cannot distinguish ensembles that produce…

Quantum Physics · Physics 2026-05-29 Cameron Hahn , Nishan Ranabhat , Fabio Anza

A fundamental problem in Quantum Information Processing is the discrimination amongst a set of quantum states of a system. In this paper, we address this problem on an open quantum system described by a graph, whose evolution is defined by…

Quantum Physics · Physics 2020-10-07 Nicola Dalla Pozza , Filippo Caruso

Quantum state discrimination is a fundamental primitive in quantum statistics where one has to correctly identify the state of a system that is in one of two possible known states. A programmable discrimination machine performs this task…

Quantum Physics · Physics 2015-05-19 G. Sentís , E. Bagan , J. Calsamiglia , R. Munoz-Tapia

The standard quantum state discrimination problem can be understood as a communication scenario involving a sender and a receiver following these three steps: (i) the sender encodes information in pre-agreed quantum states, (ii) sends them…

Quantum Physics · Physics 2024-06-28 Spiros Kechrimparis , James Moran , Athena Karsa , Changhyoup Lee , Hyukjoon Kwon

There are fundamental limits to the accuracy with which one can determine the state of a quantum system. I give an overview of the main approaches to quantum state discrimination. Several strategies exist. In quantum hypothesis testing, a…

Quantum Physics · Physics 2009-11-06 Anthony Chefles