Delegated quantum computation enables a client with limited quantum capabilities to outsource computations to a more powerful quantum server while preserving correctness and privacy. Verification is crucial in this setting to ensure that the untrusted quantum server performs the computation honestly and returns correct results. A common verification method is the quantum cut-and-choose technique. Inspired by classical verification methods for two-party computation, the client uses the majority of the delegated rounds to test the server's honesty, while keeping the remaining ones for the actual computation. Combining this technique with other methods, such as quantum error correction, could help achieve negligible cheating probabilities for the server; however, such methods can impose significant overheads making implementations unfeasible for the near-term future. In this work, we investigate whether cut-and-choose can yield efficient and secure verifiable quantum computation without additional costly techniques. We find that verifiable delegated quantum computation protocols relying solely on cut-and-choose techniques cannot be secure and efficient at the same time.

翻译：委托量子计算使得量子能力有限的客户能够将计算任务外包给能力更强的量子服务器，同时保证计算的正确性与隐私性。在此场景下，验证机制至关重要，以确保不可信的量子服务器诚实地执行计算并返回正确结果。一种常见的验证方法是量子“切分-选择”技术。受经典两方计算验证方法的启发，客户利用大部分委托轮次来测试服务器的诚实性，而将剩余轮次用于实际计算。将该技术与量子纠错等其他方法结合，可能帮助实现服务器作弊概率可忽略不计；然而，这类方法可能带来显著的开销，使得在近期未来难以实现。本工作中，我们探究了在不引入额外昂贵技术的前提下，“切分-选择”能否实现高效且安全的可验证量子计算。我们发现，仅依赖“切分-选择”技术的可验证委托量子计算协议无法同时满足安全性与高效性。