Delegating Private Quantum Computations

TL;DR

This paper presents a protocol enabling a client to delegate quantum computations on encrypted data to a server, with improved efficiency and security, allowing the server to perform universal quantum gates with minimal interaction.

Contribution

It introduces a new protocol for delegated quantum computation that reduces auxiliary qubits and communication, enhancing privacy and practicality over previous methods.

Findings

Non-interactive Clifford gates on encrypted data

Single auxiliary qubit for non-Clifford gate implementation

Security against adversarial servers via simulation-based proof

Abstract

We give a protocol for the delegation of quantum computation on encrypted data. More specifically, we show that in a client-server scenario, where the client holds the encryption key for an encrypted quantum register held by the server, it is possible for the server to perform a universal set of quantum gates on the quantum data. All Clifford group gates are non-interactive, while the remaining non-Clifford group gate that we implement (the p/8 gate) requires the client to prepare and send a single random auxiliary qubit (chosen among four possibilities), and exchange classical communication. This construction improves on previous work, which requires either multiple auxiliary qubits or two-way quantum communication. Using a reduction to an entanglement-based protocol, we show privacy against any adversarial server according to a simulation-based security definition.