Regensburg 2004 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 25: FV-internes Symposium ”Superconducting Qubits and π-junctions”

TT 25.1: Fachvortrag

Donnerstag, 11. März 2004, 09:30–10:00, H20

Charge-phase Josephson qubit with radio frequency readout — •Alexander Zorin — PTB, Bundesallee 100, 38116 Braunschweig

A solid state qubit presenting a macroscopic superconducting ring including two small tunnel Josephson junctions is considered. A pulsed gate voltage polarizing a small island between the junctions and a variable magnetic flux applied to the ring make it possible quantum manipulations of the system state. Readout of the state is performed by probing the effective Josephson inductance of the qubit. This is done by inducing low-frequency harmonic oscillations in inductively coupled tank circuit and measuring the resonance frequency shift. On one hand, this narrow-band readout system requires sufficiently long time for a single measurement. On the other hand, due to the qubit symmetry and its disconnection from dc bias lines and, presumably, from microwave-frequency noise sources it should be safely decoupled from environment and exhibit rather long coherence and relaxation times. The issues related to optimization of the qubit characteristics and regime of its operation will be addressed in the talk. The results of first experiments will be also reported.