How is photon-blockade breakdown different from optical bistability? A neoclassical story

The photon-blockade breakdown bistability can be intuitively explained invoking the energy spectrum of the interacting qubit-mode system. Yet, the neoclassical solution of the driven-dissipative Jaynes-Cummings model has been shown to capture several key aspects of the phenomenon. In this paper, we set out to compare a fully quantum solution with the neo- and semiclassical solutions. Although the neoclassical theory is founded on the assumption of a pure partial state for the qubit, it is not simply the γ →0 limit of the semiclassical theory, the semi- versus neoclassical duality being a case of non-commutativity of limits. Furthermore, we show that the neoclassical predictions still hold in the case of a small qubit decay. Tracing the bistable behavior for different detunings, we show that it is robust over a significant range of Δ values. We demonstrate that the aptitude of the neoclassical description is founded on the high quantum purity of the bright state of the photon-blockade breakdown bistability, which sharply differentiates this phenomenology from conventional optical bistability. It is thereby demonstrated that driven-dissipative dynamics can produce closely separable pure steady states in an interacting bipartite.