Multi-party quantum computation (MPQC) allows a set of parties to securely compute a quantum circuit over private quantum data. Current MPQC protocols rely on the fact that the network is synchronous, i.e., messages sent are guaranteed to be delivered within a known fixed delay upper bound, and unfortunately completely break down even when only a single message arrives late. Motivated by real-world networks, the seminal work of Ben-Or, Canetti and Goldreich (STOC'93) initiated the study of multi-party computation for classical circuits over asynchronous networks, where the network delay can be arbitrary. In this work, we begin the study of asynchronous multi-party quantum computation (AMPQC) protocols, where the circuit to compute is quantum. Our results completely characterize the optimal achievable corruption threshold: we present an n-party AMPQC protocol secure up to t < n/4 corruptions, and an impossibility result when t ≥ n/4 parties are corrupted. Remarkably, this characterization differs from the analogous classical setting, where the optimal corruption threshold is t < n/3.
@InProceedings{goyal_et_al:LIPIcs.ITCS.2023.62, author = {Goyal, Vipul and Liu-Zhang, Chen-Da and Raizes, Justin and Ribeiro, Jo\~{a}o}, title = {{Asynchronous Multi-Party Quantum Computation}}, booktitle = {14th Innovations in Theoretical Computer Science Conference (ITCS 2023)}, pages = {62:1--62:22}, series = {Leibniz International Proceedings in Informatics (LIPIcs)}, ISBN = {978-3-95977-263-1}, ISSN = {1868-8969}, year = {2023}, volume = {251}, editor = {Tauman Kalai, Yael}, publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik}, address = {Dagstuhl, Germany}, URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ITCS.2023.62}, URN = {urn:nbn:de:0030-drops-175655}, doi = {10.4230/LIPIcs.ITCS.2023.62}, annote = {Keywords: Quantum Cryptography, Multiparty Computation, Asynchronous} }
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