Feedback-induced nonlinearity and superconducting on-chip quantum optics

  1. Zhong-Peng Liu,
  2. Hui Wang,
  3. Jing Zhang,
  4. Yu-xi Liu,
  5. Re-Bing Wu,
  6. and Franco Nori
Quantum coherent feedback has been proven to be an efficient way to tune the dynamics of quantum optical systems and, recently, those of solid-state quantum circuits. Here, inspired
by the recent progress of quantum feedback experiments, especially those in mesoscopic circuits, we prove that superconducting circuit QED systems, shunted with a coherent feedback loop, can change the dynamics of a superconducting transmission line resonator, i.e., a linear quantum cavity, and lead to strong on-chip nonlinear optical phenomena. We find that bistability can occur under the semiclassical approximation, and photon anti-bunching can be shown in the quantum regime. Our study presents new perspectives for engineering nonlinear quantum dynamics on a chip.

From blockade to transparency: controllable photon transmission through a circuit QED system

  1. Yu-xi Liu,
  2. Xun-Wei Xu,
  3. Adam Miranowicz,
  4. and Franco Nori
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 analyze
the 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.