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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Cite this article
APA 7
Sajnok, K., & Costa, F. (2026). Multi-time advantage for certifying quantum coherence. https://omanscience.com/en/articles/multi-time-advantage-for-certifying-quantum-coherence
MLA 9
Sajnok, Karol, and Fabio Costa. "Multi-time advantage for certifying quantum coherence." https://omanscience.com/en/articles/multi-time-advantage-for-certifying-quantum-coherence.
Chicago (author–date)
Sajnok, Karol, and Fabio Costa. 2026. "Multi-time advantage for certifying quantum coherence." https://omanscience.com/en/articles/multi-time-advantage-for-certifying-quantum-coherence.
Harvard
Sajnok, K. and Costa, F. (2026) 'Multi-time advantage for certifying quantum coherence', Available at: https://omanscience.com/en/articles/multi-time-advantage-for-certifying-quantum-coherence.
Vancouver
Sajnok K, Costa F. Multi-time advantage for certifying quantum coherence. https://omanscience.com/en/articles/multi-time-advantage-for-certifying-quantum-coherence
IEEE
K. Sajnok, and F. Costa, "Multi-time advantage for certifying quantum coherence," https://omanscience.com/en/articles/multi-time-advantage-for-certifying-quantum-coherence.