Narrow bounds for the quantum capacity of thermal attenuators
Rosati, Matteo (Universitat Autònoma de Barcelona. Departament de Física)
Mari, Andrea (Scuola Normale Superiore and Istituto Nanoscienze)
Giovannetti, Vittorio (Scuola Normale Superiore and Istituto Nanoscienze)

Date:	2018
Abstract:	Thermal attenuator channels model the decoherence of quantum systems interacting with a thermal bath, e. g. , a two-level system subject to thermal noise and an electromagnetic signal traveling through a fiber or in free-space. Hence determining the quantum capacity of these channels is an outstanding open problem for quantum computation and communication. Here we derive several upper bounds on the quantum capacity of qubit and bosonic thermal attenuators. We introduce an extended version of such channels which is degradable and hence has a single-letter quantum capacity, bounding that of the original thermal attenuators. Another bound for bosonic attenuators is given by the bottleneck inequality applied to a particular channel decomposition. With respect to previously known bounds we report better results in a broad range of attenuation and noise: we can now approximate the quantum capacity up to a negligible uncertainty for most practical applications, e. g. , for low thermal noise.
Grants:	Ministerio de Economía y Competitividad FIS2016-80681-P Agència de Gestió d'Ajuts Universitaris i de Recerca 2017/SGR-1127
Note:	Correccions a aquest document es poden consultar a a https://ddd.uab.cat/record/226311
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Language:	Anglès
Document:	Article ; recerca ; Versió publicada
Subject:	Quantum information ; Quantum optics ; Qubits ; Theoretical physics
Published in:	Nature communications, Vol. 9 (October 2018) , art. 4339, ISSN 2041-1723

DOI: 10.1038/s41467-018-06848-0
PMID: 30337632

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