Activation and superactivation of single-mode Gaussian quantum channels

Abstract

Activation of quantum capacity is a surprising phenomenon according to which the quantum capacity of a certain channel may increase by combining it with another channel with zero quantum capacity. Superactivation describes an even more particular occurrence, in which both channels have zero quantum capacity, but their composition has a nonvanishing one. We investigate these effects for all single-mode phase-insensitive Gaussian channels, which include thermal attenuators and amplifiers, assisted by a two-mode positive-partial-transpose channel. Our result shows that activation phenomena are special but not uncommon. We can reveal superactivation in a broad range of thermal attenuator channels, even when the transmissivity is quite low. This means that we can transmit quantum information reliably through very noisy Gaussian channels having zero quantum capacity. We further show that no superactivation is possible for entanglement-breaking Gaussian channels in physically relevant circumstances by proving the non-activation property of the coherent information of bosonic entanglement-breaking channels with finite input energy.

arXiv comment11 pages, 2 figures; minor changes, references are added

References in corpus (22)

• Gaussian Quantum Information
• Fundamental Limits of Repeaterless Quantum Communications
• General Benchmarks for Quantum Repeaters
• Continuous variable quantum information: Gaussian states and beyond
• Superadditivity of communication capacity using entangled inputs
• From Classical to Quantum Shannon Theory
• Bound entangled Gaussian states
• Quantum Communication With Zero-Capacity Channels
• Quantum Channel Capacity of Very Noisy Channels
• Multipartite entanglement in three-mode Gaussian states of continuous variable systems: Quantification, sharing structure and decoherence
• Improved quantum capacity bounds of Gaussian loss channels and achievable rates with Gottesman-Kitaev-Preskill codes
• Degenerate Quantum Codes for Pauli Channels
• The private capacity of quantum channels is not additive
• Multi-mode bosonic Gaussian channels
• Gaussian bosonic synergy: quantum communication via realistic channels of zero quantum capacity
• Structured Codes Improve the Bennett-Brassard-84 Quantum Key Rate
• Narrow Bounds for the Quantum Capacity of Thermal Attenuators
• The Holevo capacity of infinite dimensional channels and the additivity problem
• Random quantum codes from Gaussian ensembles and an uncertainty relation
• Activation of quantum capacity of Gaussian channels
• Standard super-activation for Gaussian channels requires squeezing
• Coherent information of one-mode Gaussian channels -- the general case of nonzero added classical noise

Cited by in corpus (9)

• Enhanced energy-constrained quantum communication over bosonic Gaussian channels
• Estimating Quantum and Private capacities of Gaussian channels via degradable extensions
• Generic nonadditivity of quantum capacity in simple channels
• Entropic singularities give rise to quantum transmission
• Upper bounds on the quantum capacity for general attenuator and amplifier
• How Deep the Theory of Quantum Communications Goes: Superadditivity, Superactivation and Causal Activation
• Allowing leakage can increase quantum transmission
• Additivity of quantum capacities in simple non-degradable quantum channels
• Information storage and transmission under Markovian noise