E. T. Holland

Cryogenic single-port calibration for superconducting microwave resonator measurements

  1. Haozhi Wang,
  2. S. Singh,
  3. C.R.H. McRae,
  4. J.C. Bardin,
  5. S.-X. Lin,
  6. N. Messaoudi,
  7. A.R. Castelli,
  8. Y. J. Rosen,
  9. E. T. Holland,
  10. D. P. Pappas,
  11. and J. Y. Mutus
Superconducting circuit testing and materials loss characterization requires robust and reliable methods for the extraction of internal and coupling quality factors of microwave resonators.
A common method, imposed by limitations on the device design or experimental configuration, is the single-port reflection geometry, i.e. reflection-mode. However, impedance mismatches in cryogenic systems must be accounted for through calibration of the measurement chain while it is at low temperatures. In this paper, we demonstrate a data-based, single-port calibration using commercial microwave standards and a vector network analyzer (VNA) with samples at millikelvin temperature in a dilution refrigerator, making this method useful for measurements of quantum phenomena. Finally, we cross reference our data-based, single-port calibration and reflection measurement with over-coupled 2D- and 3D-resonators against well established two-port techniques corroborating the validity of our method.
arxiv pdf

Single-photon Resolved Cross-Kerr Interaction for Autonomous Stabilization of Photon-number States

  1. E. T. Holland,
  2. B. Vlastakis,
  3. R. W. Heeres,
  4. M. J. Reagor,
  5. U. Vool,
  6. Z. Leghtas,
  7. L. Frunzio,
  8. G. Kirchmair,
  9. M. H. Devoret,
  10. M. Mirrahimi,
  11. and R. J. Schoelkopf
Quantum states can be stabilized in the presence of intrinsic and environmental losses by either applying active feedback conditioned on an ancillary system or through reservoir engineering.
Reservoir engineering maintains a desired quantum state through a combination of drives and designed entropy evacuation. We propose and implement a quantum reservoir engineering protocol that stabilizes Fock states in a microwave cavity. This protocol is realized with a circuit quantum electrodynamics platform where a Josephson junction provides direct, nonlinear coupling between two superconducting waveguide cavities. The nonlinear coupling results in a single photon resolved cross-Kerr effect between the two cavities enabling a photon number dependent coupling to a lossy environment. The quantum state of the microwave cavity is discussed in terms of a net polarization and is analyzed by a measurement of its steady state Wigner function.
arxiv pdf