Characterization of a two-transmon processor with individual single-shot qubit readout

TL;DR

This paper details the characterization of a two-transmon superconducting qubit processor with individual single-shot readout, demonstrating high-fidelity gate operations and Bell inequality violation.

Contribution

It presents the first detailed characterization of a two-transmon system with individual readout, including gate fidelity and quantum correlations.

Findings

Achieved a 90% gate fidelity for the SWAP gate.

Observed Bell inequality violation by 22 standard deviations.

Demonstrated coherent two-qubit dynamics via state tomography.

Abstract

We report the characterization of a two-qubit processor implemented with two capacitively coupled tunable superconducting qubits of the transmon type, each qubit having its own non-destructive single-shot readout. The fixed capacitive coupling yields the \sqrt{iSWAP} two-qubit gate for a suitable interaction time. We reconstruct by state tomography the coherent dynamics of the two-bit register as a function of the interaction time, observe a violation of the Bell inequality by 22 standard deviations after correcting readout errors, and measure by quantum process tomography a gate fidelity of 90%.