Error suppression by a virtual two-qubit gate

TL;DR

This paper demonstrates that a virtual two-qubit gate (VTQG) can significantly reduce errors in superconducting quantum computers by minimizing SWAP gates, thereby improving the fidelity of quantum simulations.

Contribution

The study introduces the application of VTQG for error suppression in quantum simulations, showing its effectiveness in reducing SWAP gate overheads and improving accuracy.

Findings

One order of magnitude improvement in simulation accuracy.

VTQG reduces the need for multiple SWAP gates.

Combining VTQG with pulse-efficient transpilation further suppresses errors.

Abstract

Sparse connectivity of a superconducting quantum computer results in the large experimental overheads of SWAP gates. In this study, we consider employing a virtual two-qubit gate (VTQG) as an error suppression technique. The VTQG enables a non-local operation between a pair of distant qubits using only single qubit gates and projective measurements. Here, we apply the VTQG to the digital quantum simulation of the transverse-field Ising model on an IBM quantum computer to suppress the errors due to the noisy two-qubit operations. We present an effective use of VTQG, where the reduction of multiple SWAP gates results in increasing the fidelity of the output states. The obtained results indicate that the VTQG can be useful for suppressing the errors due to the additional SWAP gates. Additionally, by combining a pulse-efficient transpilation method with the VTQG, further suppression of the errors is observed. In our experiments, we have observed one order of magnitude improvement in accuracy for the quantum simulation of the transverse-field Ising model with 8 qubits.