Abstract

Double quantum dots made from semiconductor nanowires and carbon nanotubes have previously enabled a supercurrent, which is composed of Cooper pairs in a spin singlet state, to be split into its two component electron currents. Such a process, known as Cooper pair splitting, may be a route to quantum mechanical electrical circuits in which entanglement of the split electronic state plays a role. In contrast with these previous experiments which deal with large ensembles of split Cooper pairs, we here demonstrate that in a superconducting aluminium double quantum dot it is possible to observe splitting of a single Cooper pair and its subsequent recombination. We measure the spectrum of background microwave light responsible for the splitting and find it to be consistent with background black‐body radiation. Furthermore, we are able to apply external microwave light and observe controlled Cooper pair splitting through the absorption of a single microwave photon. The detection of single microwave photons via single Cooper pair splitting may have application in the circuit quantum electrodynamics paradigm of quantum computing.

N. J. Lambert et al. arXiv:1304.5117