2 research outputs found
Photon-noise-tolerant dispersive readout of a superconducting qubit using a nonlinear Purcell filter
Residual noise photons in a readout resonator become a major source of
dephasing for a superconducting qubit when the resonator is optimized for a
fast, high-fidelity dispersive readout. Here, we propose and demonstrate a
nonlinear Purcell filter that suppresses such an undesired dephasing process
without sacrificing the readout performance. When a readout pulse is applied,
the filter automatically reduces the effective linewidth of the readout
resonator, increasing the sensitivity of the qubit to the input field. The
noise tolerance of the device we fabricated is shown to be enhanced by a factor
of three relative to a device with a linear filter. The measurement rate is
enhanced by another factor of three by utilizing the bifurcation of the
nonlinear filter. A readout fidelity of 99.4% and a QND fidelity of 99.2% are
achieved using a 40-ns readout pulse. The nonlinear Purcell filter will be an
effective tool for realizing a fast, high-fidelity readout without compromising
the coherence time of the qubit.Comment: 13 pages, 9 figure
Photon-Noise-Tolerant Dispersive Readout of a Superconducting Qubit Using a Nonlinear Purcell Filter
Residual noise photons in a readout resonator become a major source of dephasing for a superconducting qubit when the resonator is optimized for a fast, high-fidelity dispersive readout. Here, we propose and demonstrate a nonlinear Purcell filter that suppresses such an undesirable dephasing process without sacrificing the readout performance. When a readout pulse is applied, the filter automatically reduces the effective linewidth of the readout resonator, increasing the sensitivity of the qubit to the input field. The noise tolerance of the device we have fabricated is shown to be enhanced by a factor of 3 relative to a device with a linear filter. The measurement rate is enhanced by another factor of 3 by utilizing the bifurcation of the nonlinear filter. A readout fidelity of 99.4% and a quantum nondemolition fidelity of 99.2% are achieved using a 40-ns readout pulse. The nonlinear Purcell filter will be an effective tool for realizing a fast, high-fidelity readout without compromising the coherence time of the qubit