Power-dependent internal loss in Josephson bifurcation amplifiers

Abstract

We have studied nonlinear superconducting resonators: lambda/2 coplanar-waveguide (CPW) resonators with Josephson junctions (JJs) placed in the middle and lambda/4 CPW resonators terminated by JJs, which can be used for the qubit readout as "bifurcation amplifiers." The nonlinearity of the resonators arises from the Josephson junctions, and because of the nonlinearity, the resonators with appropriate parameters are expected to show a hysteretic response to the frequency sweep, or "bifurcation," when they are driven with a sufficiently large power. We designed and fabricated resonators whose resonant frequencies were around 10 GHz. We characterized the resonators at low temperatures, T<0.05 K, and confirmed that they indeed exhibited hysteresis. The sizes of the hysteresis, however, are sometimes considerably smaller than the predictions based on the loaded quality factor in the weak drive regime. When the discrepancy appears, it is mostly explained by taking into account the internal loss, which often increases in our resonators with increasing drive power in the relevant power range. As a possible origin of the power-dependent loss, the quasiparticle channel of conductance of the JJs is discussed.

8 pages, 9 figures

References in corpus (12)

• Approaching Unit Visibility for Control of a Superconducting Qubit with Dispersive Readout
• Controlling the spontaneous emission of a superconducting transmon qubit
• Dephasing of a superconducting qubit induced by photon noise
• Quantum non-demolition measurement of a superconducting two-level system
• Microwave Dielectric Loss at Single Photon Energies and milliKelvin Temperatures
• High-contrast dispersive readout of a superconducting flux qubit using a nonlinear resonator
• Nonlinearities and Parametric Amplification in Superconducting Coplanar Waveguide Resonators
• Nondestructive readout for a superconducting flux qubit
• RF bifurcation of a Josephson junction: microwave embedding circuit requirements
• Measuring the Decoherence of a Quantronium Qubit with the Cavity Bifurcation Amplifier
• Phase-locking transition in a chirped superconducting Josephson resonator
• Nonlinear resonant behavior of the dispersive readout scheme for a superconducting flux qubit

Cited by in corpus (6)

• Microwave Down-Conversion with an Impedance-Matched $\Lambda$ System in Driven Circuit QED
• Loss mechanisms in superconducting thin film microwave resonators
• Quantum heating of a parametrically modulated oscillator: spectral signatures
• Quantum noise properties of multiphoton transitions in driven nonlinear resonators
• Material matters in superconducting qubits
• Finite Length Effects and Coulomb Interaction in Ge Quantum Well-Based Josephson Junctions Probed with Microwave Spectroscopy