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We propose to apply the notion of the Schmidt number in order to show that a quantum memory or gate process is capable of maintaining a genuine multi-level quantum coherence. We present a simple criterion in terms of an average gate…

Quantum Physics · Physics 2012-02-03 Ryo Namiki , Yuuki Tokunaga

We introduce witnesses for the average channel fidelity between a known target gate and an arbitrary unknown channel, for continuous-variable (CV) systems. These are observables whose expectation value yields a tight lower bound to the…

Quantum Physics · Physics 2021-06-29 Renato M. S. Farias , Leandro Aolita

An experimental success criterion for continuous-variable quantum teleportation and memories is to surpass a limit of the average fidelity achieved by the classical measure-and-prepare schemes with respect to a Gaussian distributed set of…

Quantum Physics · Physics 2011-04-25 Ryo Namiki

We consider the storage and transmission of a Gaussian distributed set of coherent states of continuous variable systems. We prove a limit on the average fidelity achievable when the states are transmitted or stored by a classical channel,…

Quantum Physics · Physics 2009-11-10 K. Hammerer , M. M. Wolf , E. S. Polzik , J. I. Cirac

We generalize the experimental success criterion for quantum teleportation/memory in continuous-variable quantum systems to be suitable for non-unit-gain condition by considering attenuation/amplification of the coherent-state amplitude.…

Quantum Physics · Physics 2008-09-29 Ryo Namiki , Masato Koashi , Nobuyuki Imoto

We present an uncertainty-relation-type quantum benchmark for continuous-variable (CV) quantum channels that works with an input ensemble of Gaussian distributed coherent states and homodyne measurements. It determines an optimal trade-off…

Quantum Physics · Physics 2015-04-07 Ryo Namiki , Koji Azuma

We introduce a measure of average dimensionality (or coherence) for high-dimensional quantum devices. This includes sets of quantum measurements, steering assemblages, and quantum channels. For measurements and channels, our measure…

Quantum Physics · Physics 2023-06-22 Thomas Cope , Roope Uola

While continuous-variable (CV) quantum systems are believed to be more efficient for quantum sensing and metrology than their discrete-variable (DV) counterparts due to the infinite spectrum of their native operators, our toolkit of…

Quantum Physics · Physics 2025-01-10 Xi Lu , Bojko N. Bakalov , Yuan Liu

Certifying high-dimensional quantum channels is essential for ensuring the reliability of quantum communication protocols. Existing certification schemes often rely on fully trusted internal devices, which is difficult to achieve in…

Quantum Physics · Physics 2026-02-10 Mengyan Li , Yanning Jia , Fenzhuo Guo , Haifeng Dong , Sujuan Qin , Fei Gao

We aim to devise feasible, efficient verification schemes for bosonic channels. To this end, we construct an average-fidelity witness that yields a tight lower bound for average fidelity plus a general framework for verifying optimal…

Quantum Physics · Physics 2019-07-19 Ya-Dong Wu , Barry C. Sanders

Continuous-Variable (CV) devices are a promising platform for demonstrating large-scale quantum information protocols. In this framework, we define a general quantum computational model based on a CV hardware. It consists of vacuum input…

Quantum Physics · Physics 2019-02-06 Tom Douce , Damian Markham , Elham Kashefi , Peter van Loock , Giulia Ferrini

We investigate the problem of teleporting unknown qudit states via pure quantum channels with nonmaximal Schmidt rank. This process is mapped to the problem of discriminating among nonorthogonal symmetric states which are linearly dependent…

Quantum Physics · Physics 2012-07-11 L. Neves , M. A. Solís-Prosser , A. Delgado , O. Jiménez

Quantum digital signatures (QDSs), which utilize correlated bit strings among sender and recipients, guarantee the authenticity, integrity, and nonrepudiation of classical messages based on quantum laws. Continuous-variable (CV) quantum…

Quantum Physics · Physics 2024-11-25 Yi-Fan Zhang , Wen-Bo Liu , Bing-Hong Li , Hua-Lei Yin , Zeng-Bing Chen

There is currently a significant need for robust and efficient methods for characterizing quantum devices. While there has been significant progress in this direction, there remains a crucial need to precisely determine the strength and…

Quantum Physics · Physics 2019-09-04 Arnaud Carignan-Dugas , Joel J. Wallman , Joseph Emerson

Quantum teleportation should surpass maximum fidelity thresholds possible with local measurements and classical communications. Benchmarks have been established when states are drawn from a uniform distribution of qubits or coherent states…

Quantum Physics · Physics 2026-05-26 Tomáš Opatrný , Allison Brattley , Kunal K. Das

For a given ensemble of input and target states, the classical fidelity threshold (CFT) is the maximum valve of the averaged fidelity, and it can be achieved with a measure-and-prepare operation. This quantity can be employed to verify…

Quantum Physics · Physics 2018-07-17 Long Huang , Xiaohua Wu , Tao Zhou

We analyze the performance of quantum teleportation in terms of average fidelity and fidelity deviation. The average fidelity is defined as the average value of the fidelities over all possible input states and the fidelity deviation is…

Quantum Physics · Physics 2018-03-02 Jeongho Bang , Junghee Ryu , Dagomir Kaszlikowski

The progress in quantum operations of continuous-variable (CV) schemes can be reduced to that in CV quantum teleportation. The fidelity of quantum teleportation of an optical setup is limited by the finite degree of quantum correlation…

Quantum Physics · Physics 2008-02-27 Mitsuyoshi Yukawa , Hugo Benichi , Akira Furusawa

We apply the methodology of optimal control theory to the problem of implementing quantum gates in continuous variable systems with quadratic Hamiltonians. We demonstrate that it is possible to define a fidelity measure for continuous…

Quantum Physics · Physics 2009-11-13 Rebing Wu , Raj Chakrabarti , Herschel Rabitz

Quantum communications using continuous variables are quite mature experimental techniques and the relevant theories have been extensively investigated with various methods. In this paper, we study the continuous variable quantum channels…

Quantum Physics · Physics 2009-11-11 Tao Qin , Meisheng Zhao , Yongde Zhang
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