Practical Tomography of Multi-Time Processes

Quantum Physics [Submitted on 1 Apr 2026] Practical Tomography of Multi-Time Processes Abhinash Kumar Roy, Varun Srivastava, Christina Giarmatzi, Alexei Gilchrist Characterising multi-time quantum processes is essential for analysing temporally correlated noise and for designing effective control and mitigation strategies. A complete operational description through multi-time process tomography requires an informationally complete set of probes, which necessarily includes non-deterministic intermediate operations. On present-day quantum devices, such operations are commonly implemented using mid-circuit measurements and reset, which are technologically limited and can introduce noise and overhead in terms of ancilla requirement. In this work, we study the minimal ancillary dimension required for complete characterisation of multi-time processes. We show that sequential interactions with a single qubit ancilla can generate an informationally complete family of correlated probes for processes of arbitrary length, without requiring mid-circuit measurements or reset. Our result provides a resource-efficient route for complete multi-time process tomography and establishes that one qubit of coherent ancillary memory suffices for full reconstruction of arbitrary multi-time dynamics. Comments: 10 pages including supplementary. Version 1. Comments are welcome Subjects: Quantum Physics (quant-ph) Cite as: arXiv:2604.01482 [quant-ph]   (or arXiv:2604.01482v1 [quant-ph] for this version)   https://doi.org/10.48550/arXiv.2604.01482 Focus to learn more Submission history From: Abhinash Kumar Roy [view email] [v1] Wed, 1 Apr 2026 23:38:48 UTC (122 KB) Access Paper: HTML (experimental) view license Current browse context: quant-ph < prev   |   next > new | recent | 2026-04 References & Citations INSPIRE HEP NASA ADS Google Scholar Semantic Scholar Export BibTeX Citation Bookmark Bibliographic Tools Bibliographic and Citation Tools Bibliographic Explorer Toggle Bibliographic Explorer (What is the Explorer?) Connected Papers Toggle Connected Papers (What is Connected Papers?) Litmaps Toggle Litmaps (What is Litmaps?) scite.ai Toggle scite Smart Citations (What are Smart Citations?) Code, Data, Media Demos Related Papers About arXivLabs Which authors of this paper are endorsers? | Disable MathJax (What is MathJax?)