Jun Jing

Generating NOON states in circuit QED using multi-photon resonance in the presence of counter-rotating interactions

  1. Shi-fan Qi,
  2. and Jun Jing
The NOON states are valuable quantum resources, which have a wide range of applications in quantum communication, quantum metrology, and quantum information processing. Here we propose
a fast, concise and reliable protocol for deterministically generating the NOON states of two resonators coupled to a single △-type superconducting qutrit. In particular, we derive the effective Hamiltonians at the multi-photon resonances by virtue of the strong counter-rotating interaction between the resonator modes and the qutrit. Based on these crucial effective Hamiltonians, our protocol simplifies the previous ones using the single-photon resonance and consequently reduces the number of operations for state preparation. To test the robustness of this protocol, we analyze the effects from both the decoherence including dissipation and dephasing and the crosstalk of resonator modes on the state fidelity through a Lindblad master equation in the eigenstates of the full Hamiltonian.
arxiv pdf

Controllable coupling between a nanomechanical resonator and a coplanar-waveguide resonator via a superconducting flux qubit

  1. Wei Xiong,
  2. Da-Yu Jin,
  3. Jun Jing,
  4. Chi-Hang Lam,
  5. and J. Q. You
We study a tripartite quantum system consisting of a coplanar-waveguide (CPW) resonator and a nanomechanical resonator (NAMR) connected by a flux qubit, where the flux qubit has a large
detuning from both resonators. By a unitray transformation and a second-order approximation, we obtain a strong and controllable (i.e., magnetic-field-dependent) effective coupling between the NAMR and the CPW resonator. Due to the strong coupling, vacuum Rabi splitting can be observed from the voltage-fluctuation spectrum of the CPW resonator. We further study the properties of single photon transport as inferred from the reflectance or equivalently the transmittance. We show that the reflectance and the corresponding phase shift spectra both exhibit doublet of narrow spectral features due to vacuum Rabi splitting. By tuning the external magnetic field, the reflectance and the phase shift can be varied from 0 to 1 and −π to π, respectively. The results indicate that this hybrid quantum system can act as a quantum router.
arxiv pdf