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We consider the characterization as well as the construction of quantum codes that allow to transmit both quantum and classical information, which we refer to as `hybrid codes'. We construct hybrid codes $[\![n,k{: }m,d]\!]_q$ with length…

Quantum Physics · Physics 2017-08-16 Markus Grassl , Sirui Lu , Bei Zeng

Quantum coherence is an important quantum resource which plays a pivotal role in the field of quantum information. Based on metric adjusted skew information, we define a measure of quantum uncertainty to study average coherence under…

Quantum Physics · Physics 2026-04-23 Baolong Cheng , Linlin Ye , Zhaoqi Wu

We present truly ultimate limits on covert quantum communication by exploiting quantum-mechanical properties of the Minkowski vacuum in the quantum field theory framework. Our main results are the following: We show how two parties equipped…

Quantum Physics · Physics 2016-08-24 Kamil Bradler , Timjan Kalajdzievski , George Siopsis , Christian Weedbrook

In the general theory of quantum measurement, one associates a positive semidefinite operator on a $d$-dimensional Hilbert space to each of the $n$ possible outcomes of an arbitrary measurement. In the special case of a projective…

Quantum Physics · Physics 2021-11-23 Yizhou Liu , John B. DeBrota

A class of optimal quantum repeaters for qubits is suggested. The schemes are minimal, i.e. involve a single additional probe qubit, and optimal, i.e. provide the maximum information adding the minimum amount of noise. Information gain and…

Quantum Physics · Physics 2009-11-11 Marco G. Genoni , Matteo G. A. Paris

Quantum computers process information with the laws of quantum mechanics. Current quantum hardware is noisy, can only store information for a short time, and is limited to a few quantum bits, i.e., qubits, typically arranged in a planar…

We study optimal rates for quantum communication over a single use of a channel, which itself can correspond to a finite number of uses of a channel with arbitrarily correlated noise. The corresponding capacity is often referred to as the…

Quantum Physics · Physics 2010-03-19 Francesco Buscemi , Nilanjana Datta

We consider quantum channels with one sender and two receivers, used in several different ways for the simultaneous transmission of independent messages. We begin by extending the technique of superposition coding to quantum channels with a…

Quantum Physics · Physics 2011-10-25 Jon Yard , Patrick Hayden , Igor Devetak

The optimal performance of a communication network is limited not only by the quality of point-to-point channels, but by the efficacy of its constituent technologies. Understanding the limits of quantum networks requires an understanding of…

Quantum Physics · Physics 2022-07-13 Cillian Harney , Stefano Pirandola

The work is devoted to study of quantum mutual information and coherent information -- the two important characteristics of quantum communication channel. Appropriate definitions of these quantities in the infinite-dimensional case are…

Mathematical Physics · Physics 2010-12-07 A. S. Holevo , M. E. Shirokov

Quantum channel, as the information transmitter, is an indispensable tool in quantum information theory. In this paper, we study a class of special quantum channels named the mixed-permutation channels. The properties of these channels are…

Quantum Physics · Physics 2024-01-15 Lin Zhang , Ming-Jing Zhao

We study the problem of decoding classical information encoded on quantum states at the output of a quantum channel, with particular focus on increasing the communication rates towards the maximum allowed by Quantum Mechanics. After a brief…

Quantum Physics · Physics 2017-10-25 Matteo Rosati

Pre-shared entanglement can significantly boost communication rates in the high thermal noise and low-brightness transmitter regime. In this regime, for a lossy-bosonic channel with additive thermal noise, the ratio between the…

Quantum Physics · Physics 2024-11-08 Ali Cox , Quntao Zhuang , Christos Gagatsos , Boulat Bash , Saikat Guha

Photon loss represents a major challenge for the implementation of quantum communication protocols with untrusted devices, e.g. in the device-independent (DI) or semi-DI approaches. Determining critical loss thresholds is usually done in…

Quantum Physics · Physics 2024-12-30 Michele Masini , Marie Ioannou , Nicolas Brunner , Stefano Pironio , Pavel Sekatski

Quantum information offers the promise of being able to perform certain communication and computation tasks that cannot be done with conventional information technology (IT). Optical Quantum Information Processing (QIP) holds particular…

Quantum Physics · Physics 2009-11-11 W. J. Munro , Kae Nemoto , T. P. Spiller , S. D. Barrett , Pieter Kok , R. G. Beausoleil

We consider the scenario of communicating on a $3\mhyphen$user classical-quantum broadcast channel. We undertake an information theoretic study and focus on the problem of characterizing an inner bound to its capacity region. We design a…

Information Theory · Computer Science 2025-03-14 Fatma Gouiaa , Arun Padakandla

We present a communication protocol for the erasure channel assisted by backward classical communication, which achieves a significantly better rate than the best prior result. In addition, we prove an upper bound for the capacity of the…

Quantum Physics · Physics 2013-05-29 Debbie Leung , Joungkeun Lim , Peter Shor

Although different architectures of quantum perceptrons have been recently put forward, the capabilities of such quantum devices versus their classical counterparts remain debated. Here, we consider random patterns and targets independently…

Quantum Physics · Physics 2024-02-01 Fabio Benatti , Giovanni Gramegna , Stefano Mancini , Gibbs Nwemadji

We introduce the informational power of a quantum measurement as the maximum amount of classical information that the measurement can extract from any ensemble of quantum states. We prove the additivity by showing that the informational…

Quantum Physics · Physics 2015-05-27 Michele Dall'Arno , Giacomo Mauro D'Ariano , Massimiliano F. Sacchi

We provide a generalization of quantum polar codes to quantum channels with qudit-input, achieving the symmetric coherent information of the channel. Our scheme relies on a channel combining and splitting construction, where a two-qudit…

Quantum Physics · Physics 2025-03-12 Ashutosh Goswami , Mehdi Mhalla , Valentin Savin