THURSDAY, Feb 14 , 12 p.m. 11 FLOOR OF THE GAMOW TOWER
François Nguyen
Quantronics group, CEA-Saclay France
Towards charge-phase multi quantum bit circuits
The Cooper pair box (CPB) is a simple superconducting circuit that provides a two level system suitable for making a quantum bit (qubit). The Quantronium, a modified CPB developed in our group [1], has demonstrated good quantum coherence and operability, thanks to a generic strategy for making a qubit insensitive to noise. My thesis work has consisted in designing, fabricating and characterising an iSWAP gate based on two capacitively coupled Quantroniums. Spectroscopic data and swapping oscillations between the |01> and |10> states of the two qubits have been obtained, but low readout fidelity and short T1 hindered the full characterisation of the gate. We furthermore demonstrated that charging effects are detrimental for multiqubit operation, and we moved to CPBs operated almost in the phase regime embedded in microwave resonators, as developed at Yale[2].
[1] D. Vion et al., Science 296, 886 (2003)
[2] A. Wallraff et al., Nature 431, 162 (2004)
