Wire Recycling for Quantum Circuit Optimization

TL;DR

This paper presents a method to optimize quantum circuits by recycling qubit wires based on their lifetime analysis, significantly reducing wire usage and circuit size.

Contribution

It introduces a novel wire recycling technique for quantum circuits using qubit lifetime analysis to minimize resource overhead.

Findings

Reduces wire count by over 90% in tested circuits.

Improves quantum circuit resource efficiency.

Validates approach on reversible and fault-tolerant circuits.

Abstract

Quantum information processing is expressed using quantum bits (qubits) and quantum gates which are arranged in the terms of quantum circuits. Here, each qubit is associated to a quantum circuit wire which is used to conduct the desired operations. Most of the existing quantum circuits allocate a single quantum circuit wire for each qubit and, hence, introduce a significant overhead. In fact, qubits are usually not needed during the entire computation but only between their initialization and measurement. Before and after that, corresponding wires may be used by other qubits. In this work, we propose a solution which exploits this fact in order to optimize the design of quantum circuits with respect to the required wires. To this end, we introduce a representation of the lifetimes of all qubits which is used to analyze the respective need for wires. Based on this analysis, a method is proposed which "recycles" the available wires and, by this, reduces the size of the resulting circuit. Experimental evaluations based on established reversible and fault-tolerant quantum circuits confirm that the proposed solution reduces the amount of wires by more than 90% compared to unoptimized quantum circuits.