Activation and superactivation of single-mode Gaussian quantum channels

Lim, Youngrong; Takagi, Ryuji; Adesso, Gerardo; Lee, Soojoon

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, or the thermal noise is high. This means that we can transmit quantum information reliably through very noisy Gaussian channels with the help of another Gaussian channel, whose quantum capacity is also zero. We further show that no superactivation is possible for entanglement-breaking Gaussian channels in physically relevant circumstances by proving the nonactivation property of the coherent information of bosonic entanglement-breaking channels with finite input energy.

Citation

Lim, Y., Takagi, R., Adesso, G., & Lee, S. (2019). Activation and superactivation of single-mode Gaussian quantum channels. Physical Review A, 99(3), Article 032337. https://doi.org/10.1103/physreva.99.032337

• Journal Article Type: Article
• Acceptance Date: Mar 7, 2019
• Online Publication Date: Mar 25, 2019
• Publication Date: 2019-03
• Deposit Date: Mar 28, 2019
• Publicly Available Date: Mar 28, 2019
• Journal: Physical Review A
• Print ISSN: 2469-9926
• Electronic ISSN: 2469-9934
• Publisher: American Physical Society
• Peer Reviewed: Peer Reviewed
• Volume: 99
• Issue: 3
• Article Number: 032337
• DOI: https://doi.org/10.1103/physreva.99.032337
• Public URL: https://nottingham-repository.worktribe.com/output/1698892
• Publisher URL: https://journals.aps.org/pra/abstract/10.1103/PhysRevA.99.032337
• Additional Information: ©2019 American Physical Society