QUROPE Quantum Information Processing and Communication in Europe

The Chalmers team led by Chris Wilson recently published a paper in Physical Review Letters in which they investigated the effective interaction between two microwave fields, mediated by a transmon-type superconducting artificial atom that is strongly coupled to a coplanar transmission line. The interaction between the fields and atom produces an effective cross–Kerr coupling. The group demonstrated average cross–Kerr phase shifts of up to 20 degrees per photon with both coherent microwave fields at the single-photon level. Their results provide an important step toward quantum applications with propagating microwave photons.