Paper 2024/1829

Compiled Nonlocal Games from any Trapdoor Claw-Free Function

Abstract

A recent work of Kalai et al. (STOC 2023) shows how to compile any multi-player nonlocal game into a protocol with a single computationally-bounded prover. Subsequent works have built on this to develop new cryptographic protocols, where a completely classical client can verify the validity of quantum computations done by a quantum server — classical verification of quantum computations, for short. Their compiler relies on the existence of quantum fully homomorphic encryption. In this work, we propose a new compiler for transforming nonlocal games into single-prover protocols. Our compiler is based on a novel blind classical delegation of quantum computation protocol, constructed within the framework of measurement-based quantum computation. The latter construction combines a new blind remote state preparation protocol with a generalization of the universal blind quantum computation protocol by Broadbent, Fitzsimons, and Kashefi (FOCS 2009). These two constructions may also be of independent interest, as the techniques employed could enable the blind construction of more specific quantum states, and the generalized framework allows for the use of blind quantum computation in a broader range of applications, particularly in quantum cryptographic protocols. The compiler can be instantiated assuming the existence of any plain trapdoor claw-free function. Leveraging results by Natarajan and Zhang (FOCS 2023) on compiled nonlocal games, our work implies the existence of new protocols for classically verifying quantum computations based on a broader range of computational assumptions, potentially weaker than those previously known.