Reqomp: Space-constrained Uncomputation for Quantum Circuits

TL;DR

Reqomp is a method for automatically optimizing quantum circuits by uncomputing ancilla qubits to reduce qubit usage without significantly increasing gate count, addressing hardware constraints.

Contribution

It introduces Reqomp, a novel automated approach for synthesizing uncomputation in quantum circuits that balances qubit and gate resource trade-offs.

Findings

Reduces ancilla qubits by up to 96%

Decreases qubit requirements by at least 25% in 80% of benchmarks

Never increases gate count beyond 28%

Abstract

Quantum circuits must run on quantum computers with tight limits on qubit and gate counts. To generate circuits respecting both limits, a promising opportunity is exploiting uncomputation to trade qubits for gates. We present Reqomp, a method to automatically synthesize correct and efficient uncomputation of ancillae while respecting hardware constraints. For a given circuit, Reqomp can offer a wide range of trade-offs between tightly constraining qubit count or gate count. Our evaluation demonstrates that Reqomp can significantly reduce the number of required ancilla qubits by up to 96%. On 80% of our benchmarks, the ancilla qubits required can be reduced by at least 25% while never incurring a gate count increase beyond 28%.