Recent experiments in circuit QED setups have demonstrated the high probability splitting of single-photons, a phenomenon rarely observed in nature. This exotic effect is enabled by a high-impedance Josephson transmission line which increases the effective coupling of the microwave photons to an artificial atom, and provides a useful tool to probe fundamental phenomena in many-body systems.
I will a discuss a collaboration with the Manucharyan group, in which we observed the Schmid-Bulgadaev quantum phase transition, whose lack of clear evidence has sparked a recent debate, through the lens of single-photon splitting. The experimental system realizes the boundary sine-Gordon model, which is known to be integrable and is characterized by purely elastic scattering of elementary excitations, that seems at odds with photon splitting. I will show that a nonlinear relation between these excitations and the photons not only allows for inelastic decay of the latter, but also that integrability provides powerful analytical tools yielding exact results for the total inelastic decay rate and the spectrum of the resulting photons. Our results shed light on the Schmid-Bulgadaev transition, and compare nicely with measurements by the Manucharyan group.
Host: Benjamin Remez