Realization of High-Fidelity CZ and ZZ-Free iSWAP Gates with a Tunable Coupler

作     者：Youngkyu Sung Leon Ding Jochen Braumüller Antti Vepsäläinen Bharath Kannan Morten Kjaergaard Ami Greene Gabriel O. Samach Chris McNally David Kim Alexander Melville Bethany M. Niedzielski Mollie E. Schwartz Jonilyn L. Yoder Terry P. Orlando Simon Gustavsson William D. Oliver 

作者机构：Research Laboratory of Electronics Massachusetts Institute of Technology Cambridge Massachusetts 02139 USA Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology Cambridge Massachusetts 02139 USA Department of Physics Massachusetts Institute of Technology Cambridge Massachusetts 02139 USA MIT Lincoln Laboratory Lexington Massachusetts 02421 USA 

出 版 物：《Physical Review X》 (Phys. Rev. X)

年 卷 期：2021年第11卷第2期

页      面：021058-021058页

核心收录：

学科分类：07[理学] 0702[理学-物理学] 

基　　金：Air Force, (FA8721-05-C-0002) Assistant Secretary of Defense for Research and Engineering Army Research Office, ARO, (W911NF-18-1-0411) Army Research Office, ARO International Business Machines Corporation, IBM National Defense Science and Engineering Graduate, NDSEG Korea Foundation for Advanced Studies, KFAS 

主　　题：Cavity quantum electrodynamics Quantum control Quantum gates Quantum information with solid state qubits Quantum optics with artificial atoms Superconducting quantum optics 

摘      要：High-fidelity two-qubit gates at scale are a key requirement to realize the full promise of quantum computation and simulation. The advent and use of coupler elements to tunably control two-qubit interactions has improved operational fidelity in many-qubit systems by reducing parasitic coupling and frequency crowding issues. Nonetheless, two-qubit gate errors still limit the capability of near-term quantum applications. The reason, in part, is that the existing framework for tunable couplers based on the dispersive approximation does not fully incorporate three-body multilevel dynamics, which is essential for addressing coherent leakage to the coupler and parasitic longitudinal (ZZ) interactions during two-qubit gates. Here, we present a systematic approach that goes beyond the dispersive approximation to exploit the engineered level structure of the coupler and optimize its control. Using this approach, we experimentally demonstrate CZ and ZZ-free iSWAP gates with two-qubit interaction fidelities of 99.76±0.07% and 99.87±0.23%, respectively, which are close to their T1 limits.