Design and Simulation of Microwave Attenuators for Superconducting Quantum Devices

ORAL

Abstract

We have found that dephasing times for quantum superconducting transmons operating nominally at T $=$ 20 mK can be limited by thermal photons in the read-out cavity due to non-equilibrium noise on our input microwave line. In an effort to reduce this noise, we have used finite-element simulations to design attenuators that provide better thermalization of the input microwave signals being delivered to our devices. Our thermal simulations incorporate both electron-phonon decoupling effects due to dissipated power in each element of the attenuator as well as phonon thermal conduction and Kapitza boundary effects. We combine the resulting thermal map with a thermal noise model of each dissipative element of the filter to estimate the effective noise temperature of our filter design.

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Authors

  • Jay LeFebvre

    Department of Physics, University of Maryland, College Park

  • Jen-Hao Yeh

    Laboratory for Physical Sciences, College Park, MD and Department of Physics, University of Maryland, College Park, MD

  • F.C. Wellstood

    Department of Physics, University of Maryland, College Park, MD and Joint Quantum Institute, University of Maryland, College Park, JQI, CNAM, Department of Physics, University of Maryland

  • Benjamin Palmer

    Laboratory for Physical Sciences, College Park, MD and Department of Physics, University of Maryland, College Park, MD, Department of Physics, University of Maryland; Laboratory for Physical Sciences, Laboratory of Physical Sciences, College Park