Berlin 2005 – scientific programme

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TT: Tiefe Temperaturen

TT 13: Transport - Quantum Coherence and Quantum Information Systems

TT 13.15: Talk

Saturday, March 5, 2005, 12:30–12:45, TU H3027

Spectroscopic Investigation of Dynamic Features of a Ring-Type Charge Qubit — •Thomas Wagner¹, Detlef Born², Vladimir Shnyrkov², Wolfram Krech², Evgeni Il’ichev¹, and Hans-Georg Meyer¹ — ¹IPHT Jena — ²Institut für Festkörperphysik, FSU Jena

We investigated dynamic properties of a special Josephson charge qubit consisting of a single-Cooper-pair transistor (with capacitive gate) closed by a superconductive loop. First, focussing the considerations on the term of the effective Josephson inductance, we sketch theoretically some quantum-dynamic features of the qubit depending on gate charge and total phase of the transistor within a two-level model. Second, we report on the experimental implementation of the ring-type charge qubit conception. For readout purposes, the interferometer loop is inductively coupled to a radio frequency tank circuit (e.g. in flip-chip configuration). In this arrangement, the tank serves as inductance detector or spectrometer, respectively. Applying external microwaves to the device, we obtained inductance alterations connected with redistributions of the energy level occupation. This way using methods of nonresonant and resonant spectroscopy, we demonstrated Landau-Zener transitions between ground and excited bands, single-photon and multiphoton absorptions, and measured the energy gap etc.