Communication through quantum-controlled noise

Author(s)
Philippe Allard Guerin, Giulia Rubino, Caslav Brukner
Abstract

In a recent series of works [Ebler et al., Phys. Rev. Lett. 120, 120502 (2018); arXiv: 1809.06655v2; arXiv: 1810.10457v2], it has been shown that the quantum superposition of causal order-the quantum switch-offers an enhancement of classical and quantum channel capacity through noisy channels, a phenomenon that was coined "causal activation." In this paper, we attempt to clarify the nature of the advantage, by comparing the quantum switch to a class of processes that can be interpreted as quantum superposition of processes with the same causal order. We show that some of these processes can match or even outperform the quantum switch at enhancing classical and quantum channel capacity, and argue that they require the same resources as the switch. We conclude, in agreement with Abbott et al. [arXiv: 1810.09826v1], that the aforementioned advantages appear to be attributable to the ability to coherently control quantum operations, and not to indefinite causal order per se.

Organisation(s)
Quantum Optics, Quantum Nanophysics and Quantum Information
External organisation(s)
Österreichische Akademie der Wissenschaften (ÖAW)
Journal
Physical Review A
Volume
99
No. of pages
6
ISSN
2469-9926
DOI
https://doi.org/10.1103/PhysRevA.99.062317
Publication date
06-2019
Peer reviewed
Yes
Austrian Fields of Science 2012
103025 Quantum mechanics
Portal url
https://ucris.univie.ac.at/portal/en/publications/communication-through-quantumcontrolled-noise(bbaf08be-dcf4-4fea-9636-206fa6ef35de).html