True photon blockade effects with arbitrarily weak nonlinearities*

Photon blockade is a paradigmatic effect where strongly driving a nonlinear photonic cavity results in a highly non-classical state exhibiting a sharp cut-off in its photon number distribution. Such states are a resource for a variety of different quantum information processing tasks. Unfortunately, the standard blockade mechanism requires extremely strong nonlinearities: they must exceed loss rates even at the few photon level. Recently an unconventional photon-blockade effect was introduced that only requires weak nonlinearities [1]. However this mechanism does not result in a sharp photon-number cutoff, and is limited to producing Gaussian states [2]. Here, we discuss and analyze an alternate route to photon blockade that also requires very weak nonlinearities, but is capable of generating highly non-Gaussian states that have a sharp photon-number cut-off. We show how our scheme can be implemented using a rather generic setup of a driven cavity mode with a Kerr (i.e Hubbard-U) type nonlinearity. Our scheme is compatible both with a variety of quantum optics platforms, as well as circuit QED setups.

[1] Liew and Savona PRL 2010
[2] Lemonde, Didier, and Clerk PRA 2014