Phys. Rev. Lett. 114, 096602 (2015)

Cooper pairs are two electrons bound together and are responsible for superconductivity. Breaking the pairs apart provides a source of entangled electrons whose quantum states cannot be described independently. Many efforts have been devoted to realize an efficient splitting process, which can be applied in quantum technologies. Now, Zhenbing Tan and colleagues report a device with efficiencies close to 10%. It consists of two graphene quantum dots electrically connected by a grounded lead of superconducting aluminium. The geometrical configuration used allows independent bias of the dots and their independent tuning with two side gates. When the energy levels of the decoupled dots are asymmetric a conductance correlation across them is detected, providing evidence of pair splitting. The efficiency obtained is larger than that predicted by current theoretical models (which therefore should be revised) and fosters expectations for quantum information solid-state-based devices.