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We propose a new class of probabilistic reversing operations on the state of a system that was disturbed by a weak measurement. It can approximately recover the original state from the disturbed state especially with an additional…

Quantum Physics · Physics 2010-09-01 Hiroaki Terashima , Masahito Ueda

We describe a technique for self consistently characterizing both the quantum state of a single qubit system, and the positive-operator-valued measure (POVM) that describes measurements on the system. The method works with only ten…

Quantum Physics · Physics 2021-07-28 A. Stephens , J. M. Cutshall , T. McPhee , M. Beck

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 a measurement scheme that validates the preparation of an $n$-qubit stabilizer state. The scheme involves a measurement of $n$ Pauli observables, a priori determined from the stabilizer state and which can be realized using…

Quantum Physics · Physics 2019-09-17 Amir Kalev , Anastasios Kyrillidis , Norbert M. Linke

We experimentally address the significance of fidelity as a figure of merit in quantum state reconstruction of discrete (DV) and continuous variable (CV) quantum optical systems. In particular, we analyze the use of fidelity in quantum…

Quantum fidelity is one of the most important measures of similarity between mixed quantum states. However, the usual formulation is cumbersome and hard to understand when encountering the first time. This work shows in a novel, elegant…

Quantum Physics · Physics 2023-10-11 Adrian Müller

Basic properties of Uhlmann's partial fidelities are discussed. Statistical interpretation in terms of POVM measurements is established. Multiplicativity properties are considered. The relationship between partial fidelities and partitioned…

Quantum Physics · Physics 2010-04-05 Alexey E. Rastegin

Efficient and accurate state estimation is essential for the optimal management of the future smart grid. However, to meet the requirements of deploying the future grid at a large scale, the state estimation algorithm must be able to…

Information Theory · Computer Science 2017-09-29 Jung-Chieh Chen , Hwei-Ming Chung , Chao-Kai Wen , Wen-Tai Li , Jen-Hao Teng

We provide a bound for the trace distance between two quantum states. The lower bound is based on the superfidelity, which provides the upper bound on quantum fidelity. One of the advantages of the presented bound is that it can be…

Quantum Physics · Physics 2009-02-11 Zbigniew Puchała , Jarosław Adam Miszczak

Based on our previous publication [U. Herzog and J. A. Bergou, Phys.Rev. A 71, 050301(R) (2005)] we investigate the optimum measurement for the unambiguous discrimination of two mixed quantum states that occur with given prior…

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

We investigate the ability of a quantum measurement device to discriminate two states or, generically, two hypothesis. In full generality, the measurement can be performed a number $n$ of times, and arbitrary pre-processing of the states…

Quantum Physics · Physics 2017-04-26 Christoph Hirche , Masahito Hayashi , Emilio Bagan , John Calsamiglia

A recursive state estimation procedure is derived for a linear time varying system with both parametric uncertainties and stochastic measurement droppings. This estimator has a similar form as that of the Kalman filter with intermittent…

Systems and Control · Computer Science 2016-11-17 Tong Zhou

We derive sampling functions for estimation of quantum state fidelity with Schr\"odinger cat-like states, which are defined as superpositions of two coherent states with opposite amplitudes. We also provide sampling functions for fidelity…

Quantum Physics · Physics 2015-06-16 Jaromir Fiurasek , Miroslav Jezek

We present a scheme to conditionally engineer an optical quantum system via continuous-variable measurements. This scheme yields high-fidelity squeezed single photon and superposition of coherent states, from input single and two photon…

Postselected quantum computation is distinguished from regular quantum computation by accepting the output only if measurement outcomes satisfy predetermined conditions. The output must be accepted with nonzero probability. Methods for…

Quantum Physics · Physics 2007-05-23 E. Knill

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…

The reconstruction of quantum states from a sufficient set of experimental data can be achieved with arbitrarily weak measurement interactions. Since such weak measurements have negligible back-action, the quantum state reconstruction is…

Quantum Physics · Physics 2010-03-16 Holger F. Hofmann

The production of conditional quantum states and quantum operations based on the result of measurement is now seen as a key tool in quantum information and metrology. We propose a new type of photon number detector. It functions…

Quantum Physics · Physics 2009-11-10 A. M. Branczyk , Tobias J. Osborne , Alexei Gilchrist , T. C. Ralph

Complementarity and entanglement are fundamental features of Quantum Mechanics that were recently related in triality equalities that involve quantum coherence, the wave aspect of a qubit, and quantum predictability and quantum…

Quantum Physics · Physics 2022-09-09 Marcos L. W. Basso , Jonas Maziero

We consider the probability by which quantum phase measurements of a given precision can be done successfully. The least upper bound of this probability is derived and the associated optimal state vectors are determined. The probability…

Quantum Physics · Physics 2009-02-14 Thomas Schürmann