Demonstration of a quantum comparator on an ion-trap quantum device

TL;DR

This paper demonstrates a quantum comparator on an ion-trap quantum device, achieving high success probabilities for integer comparisons with increasing bit widths, showcasing advances in quantum arithmetic circuit implementation.

Contribution

First experimental demonstration of a quantum comparator on a trapped-ion quantum computer with high success rates at large bit widths.

Findings

95% success at 9-bit comparison (output-only criterion)

69% success at 9-bit comparison (with ancilla correctness)

Reliable quantum comparison at scales beyond previous experiments

Abstract

Quantum computers are believed to solve a class of computational problems that are based on modular arithmetic faster than classical computers. Among the arithmetic building blocks, comparison of integer pairs is a primitive. Here we report its demonstration in the Reimei quantum computer at RIKEN, whose trapped-ion architecture provides all-to-all qubit connectivity together with high gate fidelities. We observe high success probabilities for bit widths n = 3, 5, 7, and 9: Under a conventional output-only success criterion we obtain 95% at n=9; under a stricter criterion additionally requiring the ancilla to be correct, the success is 69% at n=9. These results demonstrate reliable quantum comparison at scales far beyond those previously achieved experimentally, not only for comparators but also in the broader context of quantum arithmetic circuits.