QEnclave -- A practical solution for secure quantum cloud computing

Abstract

We introduce a secure hardware device named a QEnclave that can secure the remote execution of quantum operations while only using classical controls. This device extends to quantum computing the classical concept of a secure enclave which isolates a computation from its environment to provide privacy and tamperresistance. Remarkably, our QEnclave only performs single-qubit rotations, but can nevertheless be used to secure an arbitrary quantum computation even if the qubit source is controlled by an adversary. More precisely, attaching a QEnclave to a quantum computer, a remote client controlling the QEnclave can securely delegate its computation to the server solely using classical communication. We investigate the security of our QEnclave by modeling it as an ideal functionality named Remote State Rotation. We show that this resource, similar to previously introduced functionality of remote state preparation, allows blind delegated quantum computing with perfect security. Our proof relies on standard tools from delegated quantum computing. Working in the Abstract Cryptography framework, we show a construction of remote state preparation from remote state rotation preserving the security. An immediate consequence is the weakening of the requirements for blind delegated computation. While previous delegated protocols were relying on a client that can either generate or measure quantum states, we show that this same functionality can be achieved with a client that only transforms quantum states without generating or measuring them. It is known that blind quantum computing with information security cannot be implemented using only classical communication. Computational assumptions that circumvent this impossibility induce large overheads on the server side that prevent their practical use. Whereas our approach based on QEnclave does not increase the complexity of the problem on the server side while relying on hardware assumptions that are already used in practice for classical computations. It hence provides for the first time a feasible path towards achieving secure delegated quantum computing for various hardware platforms that are already providing their services over the cloud.