YQI Seminar - Olivier Buisson - Institut NÉEL

Event time: 
Tuesday, December 4, 2018 - 11:00am to 12:00pm
YQI Seminar Room - 4th Floor See map
17 Hillhouse Ave
Event description: 

Fast high fidelity qubit readout using cross-Kerr coupling

The most common technique of qubit readout in cQED relies on the transverse dispersive coupling between a qubit and a microwave cavity. However, despite important progresses, implementing fast high fidelity readout remains a major challenge. Indeed, inferring the qubit state is limited by the trade-off between speed and accuracy due to Purcell effect and unwanted transitions induced by readout photons in the cavity. To overcome this, we introduce a transmon molecule based on two transmons coupled by a large inductance, which is inserted inside a 3D-cavity. The full system presents one transmon –used as qubit– with an inherent cross-Kerr (longitudinal) coupling to a non-linear readout resonator, called polaron mode. This polaron mode results from the hybridization between the microwave cavity and the second mode of the transmon molecule circuit. The direct cross-Kerr coupling is a key point of our readout scheme since it protects the qubit from Purcell effect. We will present qubit readout performance with fidelity as high as 97% and discuss the quantum non-demolition properties of this novel readout.