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We describe a simple method for certifying that an experimental device prepares a desired quantum state rho. Our method is applicable to any pure state rho, and it provides an estimate of the fidelity between rho and the actual (arbitrary)…

Quantum Physics · Physics 2011-06-09 Steven T. Flammia , Yi-Kai Liu

Direct fidelity estimation is a protocol that estimates the fidelity between an experimental quantum state and a target pure state. By measuring the expectation values of Pauli operators selected through importance sampling, the method is…

Quantum Physics · Physics 2025-07-09 Júlia Barberà-Rodríguez , Mariana Navarro , Leonardo Zambrano

As a measure of the 'closeness' of two quantum states, fidelity plays a fundamental role in quantum information theory. Fidelity estimation protocols try to strike a balance between information gleaned from an experiment, and the efficiency…

We propose practical and efficient protocols for verifying bipartite pure states for any finite dimension, which can also be applied to fidelity estimation. Our protocols are based on adaptive local projective measurements with either…

Quantum Physics · Physics 2019-09-18 Zihao Li , Yun-Guang Han , Huangjun Zhu

We propose an efficient protocol to estimate the fidelity of an $n$-qubit entangled measurement device, requiring only qubit state preparations and classical data post-processing. It works by measuring the eigenstates of Pauli operators,…

Quantum Physics · Physics 2023-12-22 Zanqiu Shen , Kun Wang

Estimating the fidelity between a desired target quantum state and an actual prepared state is essential for assessing the success of experiments. For pure target states, we use functional representations that can be measured directly and…

Quantum Physics · Physics 2024-09-09 Omar Fawzi , Aadil Oufkir , Robert Salzmann

Fidelity is a fundamental measure for the closeness of two quantum states, which is important both from a theoretical and a practical point of view. Yet, in general, it is difficult to give good estimates of fidelity, especially when one…

Quantum Physics · Physics 2022-03-31 András Gilyén , Alexander Poremba

Remarkable breakthroughs in quantum science and technology are demanding for more efficient methods in analyzing quantum many-body states. A significant challenge in this field is to verify whether a quantum state prepared by quantum…

Quantum Physics · Physics 2024-10-23 Langxuan Chen , Pengfei Zhang

We study Haar-random bases and pretty good measurement for Bayesian state estimation. Given $N$ Haar-random bases we derive a bound on fidelity averaged over IID sequences of such random measurements for a uniform ensemble of pure states.…

Quantum Physics · Physics 2024-06-06 Maria Quadeer

Fidelity estimation is essential for the quality control of entanglement distribution networks. Because measurements collapse quantum states, we consider a setup in which nodes randomly sample a subset of the entangled qubit pairs to…

Quantum Physics · Physics 2022-10-10 Liangzhong Ruan

Protocols for discriminating between a pair of channels or for estimating a channel parameter can often be aided by adaptivity or by entanglement between the probe states. This can make it difficult to bound the best possible performance…

Quantum Physics · Physics 2021-10-07 Jason L. Pereira , Leonardo Banchi , Stefano Pirandola

We introduce a simulation-free method to estimate the fidelity of large quantum circuits based on the order statistics of measured output probabilities from highly entangled, chaotic states. The approach requires only the…

Quantum Physics · Physics 2025-10-16 Tobias Micklitz

We describe an optimized, self-correcting procedure for the Bayesian inference of pure quantum states. By analyzing the history of measurement outcomes at each step, the procedure returns the most likely pure state, as well as the optimal…

Quantum Physics · Physics 2015-09-14 Amir Kalev , Itay Hen

Quantum measurements with feed-forward are crucial components of fault-tolerant quantum computers. We show how the error rate of such a measurement can be directly estimated by fitting the probability that successive randomly compiled…

Quantum Physics · Physics 2025-02-04 Darian McLaren , Matthew A. Graydon , Ali Assem Mahmoud , Joel J. Wallman

Estimating the fidelity with a target state is important in quantum information tasks. Many fidelity estimation techniques present a suitable measurement scheme to perform the estimation. In contrast, we present techniques that allow the…

Quantum Physics · Physics 2024-07-12 Akshay Seshadri , Martin Ringbauer , Jacob Spainhour , Thomas Monz , Stephen Becker

A fundamental task in quantum information science is state certification: testing whether a lab-prepared $n$-qubit state is close to a given hypothesis state. In this work, we show that every pure hypothesis state can be certified using…

Quantum Physics · Physics 2025-07-16 Meghal Gupta , William He , Ryan O'Donnell

Verifying the proper preparation of quantum states is essential in modern quantum information science. Various protocols have been developed to estimate the fidelity of quantum states produced by different parties. Direct fidelity…

Quantum Physics · Physics 2024-12-11 Christopher Vairogs , Bin Yan

Fidelity estimation is a crucial component for the quality control of entanglement distribution networks. This work studies a scenario in which multiple nodes share noisy Greenberger-Horne-Zeilinger (GHZ) states. Due to the collapsing…

Quantum Physics · Physics 2024-08-20 Liangzhong Ruan

Characterizing increasingly complex quantum systems is a central task in quantum information science, yet experimental costs often scale prohibitively with system size. Certifying key properties using simple local measurements is highly…

Quantum Physics · Physics 2026-05-21 Zhenyu Du , Jinchang Liu , Elias X. Huber , Zi-Wen Liu , Xiongfeng Ma

As quantum devices become more complex and the requirements on these devices become more demanding, it is crucial to be able to verify the performance of such devices in a scalable and reliable fashion. A cornerstone task in this challenge…

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