Quantum Computing on Encrypted Data

Anne Broadbent (IQC, University of Waterloo)

 

We present a protocol that allows an almost-classical client to interact with a quantum server in order to perform a delegated quantum computation on data encrypted with the quantum one-time pad. Our construction improves on previous work in terms of the required communication resources.

We then show how to promote this protocol to be secure against both parties, without introducing any extra assumptions. This is used to show that any two-party quantum computation, specified by a unitary which acts simultaneously on the registers of both parties, can be securely implemented against any specious (quantum semi-honest) adversary, with the only additional assumption that the parties have access to an ideal quantum SWAP gate. This establishes that unitaries alone are universal for private two-party evaluation of unitaries, thus answering an open question of Dupuis, Nielsen and Salvail (Crypto 2010).