Hybrid quantum circuits combine two or more physical systems, with the goal
of harnessing the advantages and strengths of the different systems in order to
better explore new phenomenaand potentially bring about novel quantum
technologies. This article presents a brief overview of the progress achieved
so far in the field of hybrid circuits involving atoms, spins and solid-state
devices (including superconducting and nanomechanical systems). We discuss how
these circuits combine elements from atomic physics, quantum optics, condensed
matter physics, and nanoscience, and we present different possible approaches
for integrating various systems into a single circuit. In particular, hybrid
quantum circuits can be fabricated on a chip, facilitating their future
scalability, which is crucial for building future quantum technologies,
including quantum detectors, simulators and computers.
A strong photon-photon nonlinear interaction is a necessary condition for
photon blockade. Moreover, this nonlinearity can also result a bistable
behavior in the cavity field. We analyzethe relation between detecting field
and photon blockade in a superconducting circuit QED system, and show that the
photon blockade cannot occur when the detecting field is in the bistable
regime. We further demonstrate that the photon transmission through such system
can be controlled (from photon blockade to transparency) by the detecting
field. Numerical simulations show that our proposal is experimentally
realizable with current technology.
We show a systematic construction for implementing general measurements on a
single qubit, including both strong (or projection) and weak measurements. We
mainly focus on linear opticalqubits. The present approach is composed of
simple and feasible elements, i.e., beam splitters, wave plates, and polarizing
beam splitters. We show how the parameters characterizing the measurement
operators are controlled by the linear optical elements. We also propose a
method for the implementation of general measurements in solid-state qubits.