TY - JOUR
T1 - Quantifying Quantumness of Channels Without Entanglement
AU - Ku, Huan Yu
AU - Kadlec, Josef
AU - Černoch, Antonín
AU - Quintino, Marco Túlio
AU - Zhou, Wenbin
AU - Lemr, Karel
AU - Lambert, Neill
AU - Miranowicz, Adam
AU - Chen, Shin Liang
AU - Nori, Franco
AU - Chen, Yueh Nan
N1 - Funding Information:
The reported experiment was performed by J.K. under the guidance of A.Č. and K.L. The authors acknowledge Karol Bartkiewicz for his help in numerical postprocessing of our experimental data. This work is supported partially by the National Center for Theoretical Sciences and Ministry of Science and Technology, Taiwan, Grants No. MOST 110-2123-M-006-001 and No. MOST 109-2627-E-006-004, and the Army Research Office (under Grant No. W911NF-19-1-0081). H.Y. acknowledges partial support from the National Center for Theoretical Sciences and Ministry of Science and Technology, Taiwan, Grant No. MOST 110-2811-M-006-546. MTQ acknowledges the Austrian Science Fund (FWF) through the SFB project BeyondC (subproject F7103), a grant from the Foundational Questions Institute (FQXi) as part of the Quantum Information Structure of Spacetime (QISS) Project (qiss.fr). This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie Grant Agreement No. 801110 and the Austrian Federal Ministry of Education, Science and Research (BMBWF). It reflects only the authors’ view, the EU Agency is not responsible for any use that may be made of the information it contains. N.L. acknowledges partial support from JST PRESTO through Grant No. JPMJPR18GC. A.M. is supported by the Polish National Science Centre (NCN) under the Maestro Grant No. DEC-2019/34/A/ST2/00081. S.-L.C. acknowledges support from the Ministry of Science and Technology Taiwan (Grant No. MOST 110-2811-M-006-539). F.N. is supported in part by Nippon Telegraph and Telephone Corporation (NTT) Research, the Japan Science and Technology Agency (JST) [via the Quantum Leap Flagship Program (Q-LEAP) program, the Moonshot R&D Grant No. JPMJMS2061, the Japan Society for the Promotion of Science (JSPS) [via the Grants-in-Aid for Scientific Research (KAKENHI) Grant No. JP20H00134], the Army Research Office (ARO) (Grant No. W911NF-18-1-0358), the Asian Office of Aerospace Research and Development (AOARD) (via Grant No. FA2386-20-1-4069), and the Foundational Questions Institute Fund (FQXi) via Grant No. FQXi-IAF19-06. J.K. and K.L. acknowledge funding by the Czech Science Foundation (Grant No. 20-17765S) and by Palacký University (IGA_PrF_2021_004).
Publisher Copyright:
© 2022 authors. Published by the American Physical Society.
PY - 2022/6
Y1 - 2022/6
N2 - 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.
AB - 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.
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U2 - 10.1103/PRXQuantum.3.020338
DO - 10.1103/PRXQuantum.3.020338
M3 - Article
AN - SCOPUS:85131360071
VL - 3
JO - PRX Quantum
JF - PRX Quantum
SN - 2691-3399
IS - 2
M1 - 020338
ER -