On-demand antibunched photons from inelastic Cooper pair tunneling*

In most superconducting quantum circuits the Josephson junction is used in the superconducting state where it acts as a nonlinear inductor. But a small Josephson junction can be nonlinear and dissipationless also when a non-zero DC voltage below the gap is applied to it. In this case a Cooper pair current can flow through the junction when the energy 2eV of a tunneling Cooper pair can be dissipated in the linear circuit surrounding it, in the form of photons emitted into one or several of its modes [1-2]. In this inelastic Cooper-pair tunneling regime, the junction acts as a strongly nonlinear drive on the linear circuit. I will show experiments demonstrating that it can be used to generate strongly anti-bunched photons [3-4]. By replacing the Josephson junction with a DC SQUID and modulating the flux through it we can emit anti-bunched photons on demand at very high rates of the order of 100 MHz [5].
[1] T. Holst et al., PRL 73, 3455 (1994)
[2] M. Hofheinz et al., PRL 106, 217005 (2011)
[3] B. Kubala et al., Phys. Scr. T165, 014029 (2015)
[4] J. Leppäkangas et al., PRL 115, 027004 (2015)
[5] A. Grimm, PhD Thesis (UJF Grenoble, 2015)