D. P. DiVincenzo

Canonical Circuit Quantization with Non-Reciprocal Devices

  1. A. Parra-Rodriguez,
  2. I. L. Egusquiza,
  3. D. P. DiVincenzo,
  4. and E. Solano
Non-reciprocal devices effectively mimic the breaking of time-reversal symmetry for the subspace of dynamical variables that it couples, and they can be used to create chiral information
processing networks. We study how to systematically include ideal gyrators and circulators into Lagrangian and Hamiltonian descriptions of lumped-element electrical networks. The proposed theory is of wide applicability in general non-reciprocal networks on the quantum regime. We apply it to useful and pedagogical examples of circuits containing Josephson junctions and non-reciprocal ideal elements described by admittance matrices, and compare it with the more involved treatment of circuits based on non-reciprocal devices characterized by impedance and/or scattering matrices. Finally, we discuss the dual quantization of circuits containing phase-slip junctions and non-reciprocal devices.
arxiv pdf

Dispersive Qubit Measurement by Interferometry with Parametric Amplifiers

  1. Sh. Barzanjeh,
  2. D. P. DiVincenzo,
  3. and B. M. Terhal
We perform a detailed analysis of how an amplifier-based interferometer can be used to enhance the quality of a dispersive qubit measurement, such as one performed on a superconducting
transmon qubit, using homodyne detection on an amplified microwave signal. Our modeling makes a realistic assessment of what is possible in current circuit-QED experiments; in particular, we take into account the frequency-dependence of the qubit-induced phase shift for short microwaves pulses. We compare the possible signal-to-noise ratios obtainable with (single-mode) SU(1,1) interferometers with the current coherent measurement and find a considerable reduction in measurement error probability in an experimentally-accessible range of parameters.
arxiv pdf