Quantum Computing

Software Stacks for Quantum Computing

Quantum computing is the next-generation computing paradigm. We are developing an end-to-end software stack for quantum computing, including a compiler, a runtime system, and a classical quantum circuit simulator. Currently, we focus on high-performance and scalable quantum simulators for quantum circuit simulation and tensor network contraction. We successfully simulated the 42-qubit Quantum Supremacy circuit using a workstation-level computer system with many NVMe SSDs and HDDs. The current limit of a workstation-level full-state quantum-circuit simulation is around 34 qubits. However, the capability of our quantum circuit simulator (SnuQS) is 256 times bigger than conventional full-state quantum-circuit simulators. We also build a small-scale cluster with NVMe SSDs and HDDs to simulate supercomputer-level quantum circuits with our full-state simulation method.

SnuQS

SnuQS is a full-state quantum-circuit simulation framework. It exploits storage devices, such as HDDs and NVMe SSDs, to enlarge the available main memory capacity at a small cost. It uses an automatic circuit partitioning technique based on its qubit permutation and amplitude layout. Moreover, SnuQS prefetches amplitudes to overlap computation and I/O. SnuQS combines the circuit partitioning technique with the three-step qubit permutation to guarantee that the I/O operations are grouped in a contiguous block and that the block size is large enough to achieve high I/O bandwidth. The experimental result indicates that SnuQS and the proposed I/O subsystem are an effective and practical solution to scale the full-state simulation of large quantum circuits at about 300X lower cost than the DDR4 DRAM main-memory-only system.