Improving Qubit Routing by Using Entanglement Mediated Remote Gates

TL;DR

This paper presents a method to improve qubit routing in near-term quantum computers by utilizing entanglement-mediated remote gates, significantly reducing gate count and circuit depth.

Contribution

It introduces a novel compilation approach that integrates EPR-mediated remote gates into existing quantum circuit compilers for better routing efficiency.

Findings

EPR-mediated gates reduce total gate count.

Circuit depth is significantly decreased with EPR integration.

Resource trade-offs depend on the number of EPR pairs used.

Abstract

Near-term quantum computers often have connectivity constraints, i.e. restrictions, on which pairs of qubits in the device can interact. Optimally mapping a quantum circuit to a hardware topology under these constraints is a difficult task. While numerous approaches have been proposed to optimize qubit routing, the resulting gate count and depth overheads of the compiled circuits remain high due to the short-range coupling of qubits in many near-term devices. Resource states, such as Bell or Einstein-Podolsky-Rosen (EPR) pairs, can be used to mediate operations that facilitate long-range interactions between qubits. In this work, we studied some of the practical trade-offs involved in using resource states for qubit routing. We developed a method that leverages an existing state-of-the-art compiler to optimize the routing of circuits with both standard gates and EPR mediated remote controlled-NOT gates. This was then used to compile different benchmark circuits for a square grid topology, where a fraction of the qubits are used to store EPR pairs. We demonstrate that EPR-mediated operations can substantially reduce the total number of gates and depths of compiled circuits when used with an appropriate optimizing compiler that accounts for practical overheads. Our results highlight the relevance of developing efficient compilation tools that can integrate EPR-mediated operations.