Fast, High-Fidelity Conditional-Phase Gate Exploiting Leakage Interference in Weakly Anharmonic Superconducting Qubits

M A Rol; F Battistel; F K Malinowski; C C Bultink; B M Tarasinski; R Vollmer; N Haider; N Muthusubramanian; A Bruno; B M Terhal; L DiCarlo

doi:10.1103/PhysRevLett.123.120502

Fast, High-Fidelity Conditional-Phase Gate Exploiting Leakage Interference in Weakly Anharmonic Superconducting Qubits

Phys Rev Lett. 2019 Sep 20;123(12):120502. doi: 10.1103/PhysRevLett.123.120502.

Authors

M A Rol^{1

2}, F Battistel¹, F K Malinowski^{1

2}, C C Bultink^{1

2}, B M Tarasinski^{1

2}, R Vollmer^{1

2}, N Haider^{1

3}, N Muthusubramanian^{1

2}, A Bruno^{1

2}, B M Terhal^{1

4}, L DiCarlo^{1

2}

Affiliations

¹ QuTech, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, The Netherlands.
² Kavli Institute of Nanoscience, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, The Netherlands.
³ Netherlands Organisation for Applied Scientic Research (TNO), P.O. Box 96864, 2509 JG The Hague, The Netherlands.
⁴ JARA Institute for Quantum Information, Forschungszentrum Juelich, D-52425 Juelich, Germany.

PMID: 31633950
DOI: 10.1103/PhysRevLett.123.120502

Abstract

Conditional-phase (cz) gates in transmons can be realized by flux pulsing computational states towards resonance with noncomputational ones. We present a 40 ns cz gate based on a bipolar flux pulse suppressing leakage (0.1%) by interference and approaching the speed limit set by exchange coupling. This pulse harnesses a built-in echo to enhance fidelity (99.1%) and is robust to long-timescale distortion in the flux-control line, ensuring repeatability. Numerical simulations matching experiment show that fidelity is limited by high-frequency dephasing and leakage by short-timescale distortion.