QVM: Quantum Gate Virtualization Machine

Abstract

We present the Quantum Gate Virtualization Machine (QVM), an end-to-end generic system for scalable execution of large quantum circuits with high fidelity on noisy and small quantum processors (QPUs) by leveraging gate virtualization. QVM exposes a virtual circuit intermediate representation (IR) that extends the notion of quantum circuits to incorporate gate virtualization. Based on the virtual circuit as our IR, we propose the QVM compiler--an extensible compiler infrastructure to transpile a virtual circuit through a series of modular optimization passes to produce a set of optimized circuit fragments. Lastly, these transpiled circuit fragments are executed on QPUs using our QVM runtime--a scalable and parallel infrastructure to virtualize and execute circuit fragments on a set of QPUs. We evaluate QVM on IBM's 7- and 27-qubit QPUs. Our evaluation shows that our approach allows for the execution of circuits with up to double the number of qubits compared to the qubit-count of a QPU, while improving fidelity by 4.7x on average compared to larger QPUs and that we can effectively reduce circuit depths to only 40% of the original circuit depths.