Abstract
Flux-tunable transmon qubit arrays are a promising platform for quantum computation and simulation. A challenge in scaling this platform, however, is the flux crosstalk in the system. In order to exercise precise control, we need to measure this flux crosstalk, and compensate for it. Brute force approaches to flux crosstalk calibration scale quadratically with the number of qubits in the array. As we strive towards chips with hundreds of qubits, we need an extensible approach. We propose an iterative learning-based procedure to calibrate flux crosstalk. Based on statistical tests on simulated data, we have demonstrated our calibration protocol to be accurate (less than 1 MHz mean frequency error for qubits with a maximum frequency of 5 GHz) and to scale approximately linearly with array size. We have experimentally implemented this calibration protocol on planar and 3D integrated flip-chip devices, enabling precise control of qubit frequencies with an approach that will extend naturally as we fabricate larger qubit arrays.
*C.N.B. acknowledges support from the STC Center for Integrated Quantum Materials, NSF Grant No. DMR-1231319. This material is based upon work supported by the U.S. Department of Energy, Office of Science, National Quantum Information Science Research Centers, Quantum Systems Accelerator.. This research was funded in part by the National Science Foundation under grants PHY-1720311 and 1839197; and by the Under Secretary of Defense for Research and Engineering under Air Force Contract No. FA8702-15-D-0001. The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of the U.S. Government.
