Homomorphic Encryption for Quantum Annealing with Spin Reversal Transformations
This work addresses the need for secure processing of sensitive data, such as health information, on cloud-based quantum annealers, though it appears incremental as it adapts existing encryption concepts to a quantum context.
The paper tackles the problem of enabling secure computation on quantum annealers by proposing a homomorphic encryption approach based on spin reversal transformations, which incurs little to no performance penalty and reduces the performance gap between quantum and classical computing when using homomorphic encryption.
Homomorphic encryption has been an area of study in classical computing for decades. The fundamental goal of homomorphic encryption is to enable (untrusted) Oscar to perform a computation for Alice without Oscar knowing the input to the computation or the output from the computation. Alice encrypts the input before sending it to Oscar, and Oscar performs the computation directly on the encrypted data, producing an encrypted result. Oscar then sends the encrypted result of the computation back to Alice, who can decrypt it. We describe an approach to homomorphic encryption for quantum annealing based on spin reversal transformations and show that it comes with little or no performance penalty. This is in contrast to approaches to homomorphic encryption for classical computing, which incur a significant additional computational cost. This implies that the performance gap between quantum annealing and classical computing is reduced when both paradigms use homomorphic encryption. Further, homomorphic encryption is critical for quantum annealing because quantum annealers are native to the cloud -- a third party (such as untrusted Oscar) performs the computation. If sensitive information, such as health-related data subject to the Health Insurance Portability and Accountability Act, is to be processed with quantum annealers, such a technique could be useful.