Quantifying Quantumness of Channels Without Entanglement

Huan Yu Ku, Josef Kadlec, Antonín Černoch, Marco Túlio Quintino, Wenbin Zhou, Karel Lemr, Neill Lambert, Adam Miranowicz, Shin Liang Chen, Franco Nori, Yueh Nan Chen

Research output: Contribution to journalArticlepeer-review

20 Citations (Scopus)

Abstract

Quantum channels breaking entanglement, incompatibility, or nonlocality are defined as such because they are not useful for entanglement-based, one-sided device-independent, or device-independent quantum-information processing, respectively. Here, we show that such breaking channels are related to complementary tests of macrorealism, i.e., temporal separability, channel unsteerability, temporal unsteerability, and the temporal Bell inequality. To demonstrate this we first define a steerability-breaking channel, which is conceptually similar to entanglement and nonlocality-breaking channels and prove that it is identical to an incompatibility-breaking channel. A hierarchy of quantum nonbreaking channels is derived, akin to the existing hierarchy relations for temporal and spatial quantum correlations. We then introduce the concept of channels that break temporal correlations, explain how they are related to the standard breaking channels, and prove the following results. (1) A robustness-based measure for non-entanglement-breaking channels can be probed by temporal nonseparability. (2) A non-steerability-breaking channel can be quantified by channel steering. (3) Temporal steerability and nonmacrorealism can be used for, respectively, distinguishing unital steerability-breaking channels and nonlocality-breaking channels for a maximally entangled state. Finally, a two-dimensional depolarizing channel is experimentally implemented as a proof-of-principle example to demonstrate the hierarchy relation of nonbreaking channels using temporal quantum correlations.

Original languageEnglish
Article number020338
JournalPRX Quantum
Volume3
Issue number2
DOIs
Publication statusPublished - 2022 Jun
Externally publishedYes

ASJC Scopus subject areas

  • General Physics and Astronomy
  • General Computer Science
  • Applied Mathematics
  • Mathematical Physics
  • Electronic, Optical and Magnetic Materials
  • Electrical and Electronic Engineering

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