Realisation of adiabatic and diabatic CZ gates in superconducting qubits coupled with a tunable coupler

TL;DR

This paper demonstrates high-fidelity adiabatic and diabatic CZ gates in superconducting qubits with a tunable coupler, analyzing their performance, speed, and error sources to advance quantum computing scalability.

Contribution

It introduces and compares two schemes for implementing CZ gates in superconducting qubits with a tunable coupler, achieving high fidelities and analyzing error mechanisms.

Findings

Adiabatic CZ gate fidelity: 99.53%

Diabatic CZ gate fidelity: 98.72%

Diabatic gate duration: 19 ns, faster than adiabatic (30 ns)

Abstract

High fidelity two-qubit gates are fundamental for scaling up the superconducting number. We use two qubits coupled via a frequency-tunable coupler which can adjust the coupling strength, and demonstrate the CZ gate using two different schemes, adiabatic and diabatic methods. The Clifford based Randomized Benchmarking (RB) method is used to assess and optimize the CZ gate fidelity. The fidelity of adiabatic and diabatic CZ gates are 99.53(8)% and 98.72(2)%, respectively. We also analyze the errors induced by the decoherence. Comparing to 30 ns duration time of adiabatic CZ gate, the duration time of diabatic CZ gate is 19 ns, revealing lower incoherence error rate $r'_{\rm{incoherent, int}}$ = 0.0197(5) than $r_{\rm{incoherent, int}}$ = 0.0223(3).