Composably Secure Delegated Quantum Computation with Weak Coherent Pulses

Secure Delegated Quantum Computation (SDQC) protocols allow a client to delegate a quantum computation to a powerful remote server while ensuring the privacy and the integrity of its computation. Recent resource-efficient and noise-robust protocols led to experimental proofs of concept. Yet, their physical requirements are still too stringent to be added directly to the roadmap of quantum hardware vendors. To address part of this issue, this paper shows how to alleviate the necessity for the client to have a single-photon source. We describe an SDQC protocol, similar in spirit to the decoy state method used in QKD, which requires only a source of weak coherent pulses. It is noise-robust, composable, and has negligible correctness and security errors. The simplest instantiation of our protocol with only 2 intensities shows improved scaling at low transmittance and adds verifiability to previous proposals.