Breakdown of the cross-Kerr scheme for photon counting...


Breakdown of the cross Kerr scheme for photon counting

The Chalmers SOLID group recently published an article in Physical Review Letters in which they show, in the context of single-photon detection, that an atomic three-level model for a transmon in a transmission line does not support the predictions of the nonlinear polarizability model known as the cross-Kerr effect. The group managed to demonstrate that the induced displacement of a probe in the presence or absence of a single photon in the signal field, cannot be resolved above the quantum noise in the probe. This strongly suggests that cross-Kerr media are not suitable for photon counting or related single-photon applications, a conclusion that also applies to optical systems.