A Cost-Effective Quantum Boolean-Phase SWAP Gate with Only Two CNOT Gates

TL;DR

This paper introduces a novel p-SWAP quantum gate that swaps qubits with a phase difference, requiring only two CNOT gates, reducing quantum cost and circuit depth compared to the standard three-gate SWAP.

Contribution

The paper presents a cost-effective p-SWAP gate with only two CNOT gates, demonstrating improved efficiency over standard SWAP gates for quantum circuits.

Findings

23% reduction in quantum cost after transpilation

26% reduction in circuit depth after transpilation

Effective for both phase and Boolean applications

Abstract

A new Boolean-Phase swapping gate is presented with improved quantum generality and cost-effectiveness. Our swapping gate is termed the "p-SWAP gate", where p is the phase difference selected for a set of swapped qubits. The phase p is expressed in radians and $-{\pi}~{\leq}$ p ${\leq}~+{\pi}$. The generality of p-SWAP gate is demonstrated for Phase applications for selected values of p and for Boolean applications when the value of p is ignored. The cost-effectiveness of p-SWAP gate follows from the lower quantum cost and depth of its final realized (transpiled) quantum circuit, when compared to the standard SWAP gate composed of three Feynman (CNOT) gates. Specifically, our presented p-SWAP gate utilizes only two CNOT gates. The quantum circuit of the p-SWAP gate is visually designed using our previously developed Bloch sphere approach. Experimentally, after transpilation for an IBM quantum computer, the transpiled p-SWAP gate shows an approximate 23% quantum cost reduction and an approximate 26% depth minimization compared to the transpiled standard SWAP gate.