Quantum computing on encrypted data

TL;DR

This paper introduces a practical quantum encryption protocol allowing secure quantum computations on encrypted data, demonstrated experimentally with linear optics, facilitating privacy-preserving quantum cloud computing.

Contribution

It presents the first efficient quantum encryption scheme enabling arbitrary quantum computations on encrypted data, with experimental validation using linear optics.

Findings

Untrusted server can perform universal quantum gates on encrypted qubits without learning input data.

Experimental demonstration of encryption and decryption on a set of gates for arbitrary quantum computations.

Protocol requires minimal additional resources, suitable for future quantum server implementations.

Abstract

The ability to perform computations on encrypted data is a powerful tool for protecting privacy. Recently, protocols to achieve this on classical computing systems have been found. Here we present an efficient solution to the quantum analogue of this problem that enables arbitrary quantum computations to be carried out on encrypted quantum data. We prove that an untrusted server can implement a universal set of quantum gates on encrypted quantum bits (qubits) without learning any information about the inputs, while the client, knowing the decryption key, can easily decrypt the results of the computation. We experimentally demonstrate, using single photons and linear optics, the encryption and decryption scheme on a set of gates sufficient for arbitrary quantum computations. Because our protocol requires few extra resources compared to other schemes it can be easily incorporated into the design of future quantum servers. These results will play a key role in enabling the development of secure distributed quantum systems.