Candidate
Jean-Luc Francois-Xavier Orgiazzi
Title
Experimental results on decoherence and readout of coupled super conducting flux qubits in a circuit-QED
Supervisors
Lupascu, Adrian (Physics-IQC) and Majedi, Amir Hamed
Abstract
We present the results of experiments with two superconducting flux qubits coupled to a high-quality factor aluminum coplanar waveguide resonator. The flux qubits have a loop area of about 24 micron squared. The coupling to the resonator is implemented using the inductance of a shared line. The qubits are independently controlled via on-chip fast flux bias lines. Readout is performed by homodyne detection at large resonator driving power. Readout contrast exceeds 70% for each qubit. We observed long relaxation times, approaching 10 microseconds. The coherence time at the symmetry point exceeds 1 microsecond. Away from the symmetry point, decoherence is due to 1/f flux noise, with a measured density of 2.6 x 10^-6 phi0/sqrt(Hz) at 1 Hz. We discuss the implementation of a two-qubit controlled-NOT gate using the selective darkening technique [1].
[1] P. C. de Groot, J. Lisenfeld, R. N. Schouten, S. Ashhab, A. Lupascu, C. J. P. M. Harmans, and J. E. Mooij. Nat. Phys., 6(10):763-766, October 2010.