Engineering propagating cat states with driving-assisted cavity QED

We propose a method for generating optical cat states in propagating pulses based on cavity quantum electrodynamics (QED). This scheme uses multiple four-level systems (4LSs) inside an optical cavity as a light source. Time-modulating driving stimulates it to produce a superposition of coherent states entangled with the 4LSs. The postselection of an appropriate state of the 4LSs leads to a multicomponent cat state in a propagating pulse. Taking atomic decay and cavity loss into account, we optimize the cavity external loss rate to maximize the fidelity. We find that its optimum value is formulated similarly to those of other generation methods for propagating states, suggesting a universal property of cavity-QED systems interacting with fields outside the cavity.