Quantum SWAP gate realized with CZ and iSWAP gates in a superconducting architecture

TL;DR

This paper demonstrates a superconducting quantum processor capable of implementing a SWAP gate efficiently by decomposing it into an iSWAP and a CZ gate, enabling more streamlined quantum circuit compilation.

Contribution

It introduces a method to realize a SWAP gate using only one iSWAP and one CZ gate, improving over traditional multi-gate decompositions.

Findings

SWAP gate decomposed into iSWAP and CZ gates

Efficient implementation of two-qubit Clifford gates

Superconducting platform supports all two-qubit Clifford unitaries with minimal gates

Abstract

It is advantageous for any quantum processor to support different classes of two-qubit quantum logic gates when compiling quantum circuits, a property that is typically not seen with existing platforms. In particular, access to a gate set that includes support for the CZ-type, the iSWAP-type, and the SWAP-type families of gates, renders conversions between these gate families unnecessary during compilation as any two-qubit Clifford gate can be executed using at most one two-qubit gate from this set, plus additional single-qubit gates. We experimentally demonstrate that a SWAP gate can be decomposed into one iSWAP gate followed by one CZ gate, affirming a more efficient compilation strategy over the conventional approach that relies on three iSWAP or three CZ gates to replace a SWAP gate. Our implementation makes use of a superconducting quantum processor design based on fixed-frequency transmon qubits coupled together by a parametrically modulated tunable transmon coupler, extending this platform's native gate set so that any two-qubit Clifford unitary matrix can be realized using no more than two two-qubit gates and single-qubit gates.