Communication through quantum-controlled noise

Philippe Allard Guérin, Giulia Rubino, Časlav Brukner

Research output: Contribution to journalArticle (Academic Journal)peer-review

54 Citations (Scopus)
12 Downloads (Pure)


In a recent series of works [Ebler et al. Phys. Rev. Lett. 120, 120502 (2018); arXiv:1809.06655v2; arXiv:1810.10457v2], it has been proposed that the quantum superposition of causal order -- the quantum switch -- may offer an enhancement of classical and quantum channel capacity through noisy channels, a phenomena that was coined `causal activation'. In this paper we attempt to clarify the nature of the purported 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.
Original languageEnglish
Article number062317
JournalPhys. Rev. A
Issue number6
Publication statusPublished - 17 Jun 2019

Bibliographical note

8 pages, 1 figure. Published version


  • quant-ph


Dive into the research topics of 'Communication through quantum-controlled noise'. Together they form a unique fingerprint.

Cite this