Regensburg 2010 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 9: SC: Poster Session

TT 9.46: Poster

Monday, March 22, 2010, 14:00–18:00, Poster A

Microwave Fluxon Readout for Superconducting Qubits — •Kirill G. Fedorov and Alexey V. Ustinov — Physikalisches Institut, Karlsruhe Institute of Technology, Karlsruhe, Germany

We are experimentally investigating a new type of detector for very fast and weakly perturbing readout of superconducting qubits. The detection principle is based on measuring the delay time of a ballistic magnetic fluxon moving in a Josephson transmission line when passing by a qubit [1,2]. Due to magnetic perturbation the fluxon propagation delay depends on the state of the qubit. On the way towards experimental realization of fluxon detector, we report measurements of such fluxon radiation from annular Josephson junctions using a cryogenic microwave amplifier. We have measured fine structure of fluxon step on current-voltage characteristic by detecting fluxon radiation frequency. The fluxon delay by an external magnetic perturbation of 0.1 nT induces fluxon oscillations frequency shift of 1.9 MHz. This suggest that a phase shift of fluxon oscillator can be used for non-destructive repetitive measurements of the qubit state.

[1] D.V. Averin, K. Rabenstein, and V. K. Semenov, Phys. Rev. B 73, 094504 (2006).

[2] A. Fedorov, A. Shnirman, G. Schön, and A. Kidiyarova-Shevchenko, Phys. Rev. B 75, 224504 (2007).