4 research outputs found
Quantum nondemolition detection of a propagating microwave photon
The ability to nondestructively detect the presence of a single, traveling
photon has been a long-standing goal in optics, with applications in quantum
information and measurement. Realising such a detector is complicated by the
fact that photon-photon interactions are typically very weak. At microwave
frequencies, very strong effective photon-photon interactions in a waveguide
have recently been demonstrated. Here we show how this type of interaction can
be used to realize a quantum nondemolition measurement of a single propagating
microwave photon. The scheme we propose uses a chain of solid-state 3-level
systems (transmons), cascaded through circulators which suppress photon
backscattering. Our theoretical analysis shows that microwave-photon detection
with fidelity around 90% can be realized with existing technologies
Giant Cross Kerr Effect for Propagating Microwaves Induced by an Artificial Atom
We have investigated the cross Kerr phase shift of propagating microwave
fields strongly coupled to an artificial atom. The artificial atom is a
superconducting transmon qubit in an open transmission line. We demonstrate
average phase shifts of 11 degrees per photon between two coherent microwave
fields both at the single-photon level. At high control power, we observe phase
shifts up to 30 degrees. Our results provide an important step towards quantum
gates with propagating photons in the microwave regime.Comment: 5 pages, 4 figure