Data and codes for "Quantum jumps in amplitude bistability: Tracking a coherent and invertible state localization"

We investigate the nature of quantum jumps occurring between macroscopic metastable states of light in the open driven Jaynes-Cummings model. We find that, in the limit of zero spontaneous emission considered in Carmichael (2015), the jumps from a high-photon state to the vacuum state entail two stages. The first part is coherent and modelled by the localization of a state superposition, in the example of a null-measurement record predicted by quantum trajectory theory. The underlying evolution is mediated by an unstable state (which often splits to a complex of states), identified by the conditioned density matrix and the corresponding quasiprobability distribution of the cavity field. The unstable state subsequently decays to the vacuum to complete the jump. Coherence in the localization allows for inverting the null-measurement photon average about its initial value, to account for the full switch which typically lasts a small fraction of the average cavity lifetime; an asymptotic law for the jump time is established in high-amplitude bistability. This mechanism is contrasted to the jumps leading from the vacuum to the high-photon state in the bistable signal. Spontaneous emission degrades coherence in the localization, and prolongs the jumps. The datasets in the .mat files (MATLAB) correspond to the paper figure indicated in each filename. They are primarily generated from the code JCRK4_Amp_Bist.m (solving the matrix elements equations of motion by employing a 4th order Runge-Kutta method) as well as JCBist.ccÖppnas i en ny tabb (refer to the C++ library used for quantum trajectories in the main text). The code JCRK4_Amp_Bist_Kerr.mat is used only for generating data for Fig. 8, while for Fig. 6 a subset of data used for Fig. 5 has been deployed. The conditioned Q functions and density matrix barplots are generated using Qfunction.m, while steady-state results have been generated using Qfunc_bist.m (from Quantum Optics Toolbox). The code neoclassical.m generates the mean-field bistability curve pictured in Fig. 9.