CollComm: Enabling Efficient Collective Quantum Communication Based on EPR buffering

Abstract: The noisy and lengthy nature of quantum communication hinders the development of distributed quantum computing. The inefficient design of existing compilers for distributed quantum computing worsens the situation. Previous compilation frameworks couple communication hardware with the implementation of expensive remote gates. However, we discover that the efficiency of quantum communication, especially collective communication, can be significantly boosted by decoupling communication resources from remote operations, that is, the communication hardware would be used only for preparing remote entanglement, and the computational hardware, the component used to store program information, would be used for conducting remote gates. Based on the observation, we develop a compiler framework to optimize the collective communication happening in distributed quantum programs. In this framework, we decouple the communication preparation process in communication hardware from the remote gates conducted in computational hardware by buffering EPR pairs generated by communication hardware in qubits of the computational hardware. Experimental results show that the proposed framework can halve the communication cost of various distributed quantum programs, compared to state-of-the-art compilers for distributed quantum computing.