Fast microwave-driven two-qubit gates between fluxonium qubits with a transmon coupler
Siddharth Singh (TU Delft - QRD/Andersen Lab, Kavli institute of nanoscience Delft, TU Delft - QuTech Advanced Research Centre)
Eugene Y. Huang (TU Delft - QuTech Advanced Research Centre, Kavli institute of nanoscience Delft, TU Delft - QRD/Andersen Lab)
Jinlun Hu (TU Delft - QRD/Andersen Lab, Kavli institute of nanoscience Delft, TU Delft - QuTech Advanced Research Centre)
Figen Yilmaz (TU Delft - QuTech Advanced Research Centre, Kavli institute of nanoscience Delft, TU Delft - QRD/Andersen Lab)
Martijn F.S. Zwanenburg (TU Delft - QRD/Andersen Lab, Kavli institute of nanoscience Delft, TU Delft - QuTech Advanced Research Centre)
Piranavan Kumaravadivel (TU Delft - BUS/TNO STAFF)
Siyu Wang (TU Delft - Applied Sciences, Kavli institute of nanoscience Delft, TU Delft - QuTech Advanced Research Centre)
Taryn V. Stefanski (University of Bristol, TU Delft - QuTech Advanced Research Centre, TU Delft - QRD/Andersen Lab, Kavli institute of nanoscience Delft)
Christian Kraglund Andersen (TU Delft - QuTech Advanced Research Centre, TU Delft - QRD/Andersen Lab, Kavli institute of nanoscience Delft, TU Delft - Applied Sciences)
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Abstract
Two-qubit gates constitute fundamental building blocks in the realization of large-scale quantum devices. Using superconducting circuits, two-qubit gates have been implemented in various ways, with each method aiming to maximize gate fidelity. Another important goal of a new gate scheme is to minimize the complexity of gate calibration. In this work, we demonstrate a high-fidelity two-qubit gate between two fluxonium qubits, enabled by an intermediate capacitively coupled transmon. The coupling strengths between the qubits and the coupler are designed to minimize residual crosstalk while still allowing for fast gate operations. The gate is based on frequency selectively exciting the coupler using a microwave drive to complete a 2π rotation, conditional on the state of the fluxonium qubits. When successful, this drive scheme implements a conditional phase gate. Using analytically derived pulse shapes, we minimize unwanted excitations of the coupler and obtain gate errors of 10−2 for gate times below 60 ns. At longer durations, the gate performance is limited by relaxation of the coupler. Our results show how carefully designed control pulses can speed up frequency-selective entangling gates.