Digital coherent control of a superconducting qubit

• Main Authors: LeonardJr, Edward, Beck, Matthew A, Nelson, JJ, Christensen, Brad G, Thorbeck, Ted, Howington, Caleb, Opremcak, Alexander, Pechenezhskiy, Ivan V, Dodge, Kenneth, Dupuis, Nicholas P, Ku, Jaseung, Schlenker, Francisco, Suttle, Joseph, Wilen, Christopher, Zhu, Shaojiang, Vavilov, Maxim G, Plourde, Britton L. T, McDermott, Robert
• Format: Journal Article
• Language: English
• Published: 20-06-2018
• Subjects: Physics - Quantum Physics; Physics - Superconductivity
• DOI: 10.48550/arxiv.1806.07930

Phys. Rev. Applied 11, 014009 (2019) High-fidelity gate operations are essential to the realization of a
fault-tolerant quantum computer. In addition, the physical resources required
to implement gates must scale efficiently with system size. A longstanding goal
of the superconducting qubit community is the tight integration of a
superconducting quantum circuit with a proximal classical cryogenic control
system. Here we implement coherent control of a superconducting transmon qubit
using a Single Flux Quantum (SFQ) pulse driver cofabricated on the qubit chip.
The pulse driver delivers trains of quantized flux pulses to the qubit through
a weak capacitive coupling; coherent rotations of the qubit state are realized
when the pulse-to-pulse timing is matched to a multiple of the qubit
oscillation period. We measure the fidelity of SFQ-based gates to be ~95% using
interleaved randomized benchmarking. Gate fidelities are limited by
quasiparticle generation in the dissipative SFQ driver. We characterize the
dissipative and dispersive contributions of the quasiparticle admittance and
discuss mitigation strategies to suppress quasiparticle poisoning. These
results open the door to integration of large-scale superconducting qubit
arrays with SFQ control elements for low-latency feedback and stabilization.