{"paper":{"title":"Query-optimal estimation of unitary channels in diamond distance","license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","headline":"","cross_cats":["cs.DS"],"primary_cat":"quant-ph","authors_text":"Ewin Tang, Jeongwan Haah, Robin Kothari, Ryan O'Donnell","submitted_at":"2023-02-27T19:00:00Z","abstract_excerpt":"We consider process tomography for unitary quantum channels. Given access to an unknown unitary channel acting on a $\\textsf{d}$-dimensional qudit, we aim to output a classical description of a unitary that is $\\varepsilon$-close to the unknown unitary in diamond norm. We design an algorithm achieving error $\\varepsilon$ using $O(\\textsf{d}^2/\\varepsilon)$ applications of the unknown channel and only one qudit. This improves over prior results, which use $O(\\textsf{d}^3/\\varepsilon^2)$ [via standard process tomography] or $O(\\textsf{d}^{2.5}/\\varepsilon)$ [Yang, Renner, and Chiribella, PRL 202"},"claims":{"count":0,"items":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"source":{"id":"2302.14066","kind":"arxiv","version":2},"verdict":{"id":null,"model_set":{},"created_at":null,"strongest_claim":"","one_line_summary":"","pipeline_version":null,"weakest_assumption":"","pith_extraction_headline":""},"integrity":{"clean":true,"summary":{"advisory":0,"critical":0,"by_detector":{},"informational":0},"endpoint":"/pith/2302.14066/integrity.json","findings":[],"available":true,"detectors_run":[],"snapshot_sha256":"c28c3603d3b5d939e8dc4c7e95fa8dfce3d595e45f758748cecf8e644a296938"},"references":{"count":0,"sample":[],"resolved_work":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57","internal_anchors":0},"formal_canon":{"evidence_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"author_claims":{"count":0,"strong_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"builder_version":"pith-number-builder-2026-05-17-v1"}