Scaling Quantum Computations via Gate Virtualization

TL;DR

The paper introduces the Quantum Virtual Machine (QVM), a system that enables scalable, high-fidelity execution of large quantum circuits on noisy, small quantum processors by virtualizing gates and optimizing circuit execution.

Contribution

It presents a novel end-to-end system with a virtual circuit IR, an extensible compiler, and a distributed runtime for executing large quantum circuits on small, noisy QPUs.

Findings

Able to double the circuit size executable on QPUs

Improved fidelity by 4.7 times on average

Reduced circuit depths to 40% of original

Abstract

We present the Quantum Virtual 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 distributed infrastructure to virtualize and execute circuit fragments on a set of distributed QPUs. We evaluate QVM on IBM's 7- and 27-qubit QPUs. Our evaluation shows that using our system, we can scale the circuit sizes executable on QPUs up to double the size of the QPU while improving fidelity by 4.7$\times$ on average compared to larger QPUs and that we can effectively reduce circuit depths to only 40\% of the original circuit depths.