Characterization and benchmarking of a phase-sensitive two-qubit gate using direct digital synthesis

TL;DR

This paper demonstrates a flux-tunable iSWAP two-qubit gate in transmon qubits, utilizing direct digital synthesis for precise phase control, achieving high fidelity and fast operation, crucial for scalable quantum computing.

Contribution

It introduces a method for implementing and benchmarking a high-fidelity, phase-controlled iSWAP gate using DDS and a flux-tunable coupler in transmon qubits.

Findings

Achieved a 290 ns iSWAP gate operation.

Measured 2% error rate with randomized benchmarking.

Validated gate fidelity with quantum-state tomography.

Abstract

We implement an iSWAP gate with two transmon qubits using a flux-tunable coupler. Precise control of the relative phase of the qubit-control pulses and the parametric-coupler drive is achieved with a multi-channel instrument called Presto using direct digital synthesis (DDS), a promising technique for scaling up quantum systems. We describe the process of tuning and benchmarking the iSWAP gate, where the relative phase of the pulses is controlled via software. We perform the iSWAP gate in 290 ns, validate it with quantum-state tomography, and measure 2\% error with interleaved randomized benchmarking.