PreprintarXiv licencearXiv
Multi-time advantage for certifying quantum coherence
Abstract
Non-classical dynamics in open quantum systems can be hidden in temporal correlations that are invisible to standard state- and channel-based tests. We define coherence for multi-time quantum processes and show that access to intermediate times can reveal coherence absent from all corresponding pairwise channels. Incoherent processes are fixed points of dephasing on all input and output spaces, and their coherence is quantified by relative entropy. As a proof of principle, we use an Ising model in which all three pairwise channels are incoherent while the full three-time process remains coherent. We observe this multi-time coherence on a superconducting quantum processor using a coherence witness and full process tomography.
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BibTeX
@misc{sajnok2026multitime,
title = {{Multi-time advantage for certifying quantum coherence}},
author = {Karol Sajnok and Fabio Costa},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.08241},
eprint = {2610.08241},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.08241},
}
RIS
TY - UNPB
TI - Multi-time advantage for certifying quantum coherence
AU - Karol Sajnok
AU - Fabio Costa
PY - 2026
DA - 2026/10/06
PB - arXiv
DO - 10.48550/arxiv.2610.08241
UR - https://arxiv.org/abs/2610.08241
AB - Non-classical dynamics in open quantum systems can be hidden in temporal correlations that are invisible to standard state- and channel-based tests. We define coherence for multi-time quantum processes and show that access to intermediate times can reveal coherence absent from all corresponding pairwise channels. Incoherent processes are fixed points of dephasing on all input and output spaces, and their coherence is quantified by relative entropy. As a proof of principle, we use an Ising model in which all three pairwise channels are incoherent while the full three-time process remains coherent. We observe this multi-time coherence on a superconducting quantum processor using a coherence witness and full process tomography.
ER -