23 research outputs found
Rare quantum metastable states in the strongly dispersive Jaynes-Cummings oscillator
We present evidence of metastable rare quantum-fluctuation switching for the
driven dissipative Jaynes-Cummings oscillator coupled to a zero-temperature
bath in the strongly dispersive regime. We show that single-atom complex
amplitude bistability is accompanied by the appearance of a low-amplitude
long-lived transient state, hereinafter called `dark state', having a
distribution with quasi-Poissonian statistics both for the coupled qubit and
cavity mode. We find that the dark state is linked to a spontaneous flipping of
the qubit state, detuning the cavity to a low-photon response. The appearance
of the dark state is correlated with the participation of the two metastable
states in the dispersive bistability, as evidenced by the solution of the
Master Equation and single quantum trajectories.Comment: Extensively revised text, 18 revised figures (16 in main and 2 in
appendix), 38(+1) references, appendi
Simultaneous bistability of qubit and resonator in circuit quantum electrodynamics
We explore the joint activated dynamics exhibited by two quantum degrees of
freedom: a cavity mode oscillator which is strongly coupled to a
superconducting qubit in the strongly coherently driven dispersive regime.
Dynamical simulations and complementary measurements show a range of parameters
where both the cavity and the qubit exhibit sudden simultaneous switching
between two metastable states. This manifests in ensemble averaged amplitudes
of both the cavity and qubit exhibiting a partial coherent cancellation.
Transmission measurements of driven microwave cavities coupled to transmon
qubits show detailed features which agree with the theory in the regime of
simultaneous switching
Quantum phase transitions in the driven dissipative Jaynes-Cummings oscillator: From the dispersive regime to resonance
We follow the passage from complex amplitude bistability to phase bistability in the driven dissipative Jaynes-Cummings oscillator. Quasi-distribution functions in the steady state are employed, for varying qubit-cavity detuning and drive parameters, in order to track a first-order dissipative quantum phase transition up to the critical point marking a second-order transition and spontaneous symmetry breaking. We demonstrate the photon blockade breakdown in the dispersive regime, and find that the coexistence of cavity states in the regime of quantum bistability is accompanied by pronounced qubit-cavity entanglement. Focusing on the effect of quantum-activated switching for both coupled degrees of freedom, we move from a region of minimal entanglement in the dispersive regime, where we derive analytical perturbative results, to the threshold behaviour of spontaneous dressed-state polarization at resonance