Experimental Quantum Homomorphic Encryption

TL;DR

This paper demonstrates a quantum homomorphic encryption protocol using single-photon states, enabling secure, non-interactive quantum computation with potential for more complex encryption schemes.

Contribution

It introduces a practical implementation of quantum homomorphic encryption via integrated optics, combining polarization and path degrees of freedom for encryption and computation.

Findings

Successful demonstration of quantum homomorphic encryption with single photons

Encryption of input states in polarization; computation in path degree of freedom

Potential for generalizing to more complex quantum encryption protocols

Abstract

Quantum computers promise not only to outperform classical machines for certain important tasks, but also to preserve privacy of computation. For example, the blind quantum computing protocol enables secure delegated quantum computation, where a client can protect the privacy of their data and algorithms from a quantum server assigned to run the computation. However, this security comes at the expense of interaction: the client and server must communicate after each step of the computation. Homomorphic encryption, on the other hand, avoids this limitation. In this scenario, the server specifies the computation to be performed, and the client provides only the input data, thus enabling secure non-interactive computation. Here we demonstrate a homomorphic-encrypted quantum random walk using single-photon states and non-birefringent integrated optics. The client encrypts their input state in the photons' polarization degree of freedom, while the server performs the computation using the path degree of freedom. Our random walk computation can be generalized, suggesting a promising route toward more general homomorphic encryption protocols.