Regensburg 2007 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 3: Quantum Coherence and Quantum Information Systems I
TT 3.4: Talk
Monday, March 26, 2007, 10:30–10:45, H20
Reading-out the state of a flux qubit by Josephson transmission line solitons — •Arkady Fedorov1, Alexander Shnirman1, Gerd Schoen1, Andreas Poenicke1, and Anna Anna Kidiyarova-Shevchenko2 — 1Institut für Theoretische Festkörperphysik and DFG-Center for Functional Nanostructures (CFN), Universität Karlsruhe, D–76128 Karlsruhe, Germany — 2Microtechnology and Nanoscience Department, Chalmers University of Technology, 412 96 Gothenburg, Sweden
We describe the read-out process of the state of a Josephson flux qubit via solitons in a Josephson transmission line (JTL). We consider the situation where the qubit is inductively coupled to the JTL and the information about the state of the qubit is stored in the time delay of the soliton. To investigate the efficiency that can be achieved in the proposed measurement scheme for relevant experimental parameters we evaluate the delay time in three different setups: a) when the qubit is kept away from the symmetry point all the time; b) when the qubit is initially prepared at the symmetry point, but the approaching soliton pushes the qubit far from the symmetry point; c) when the qubit is near the symmetry point all the time. We analyze the relation between the delay time and the dissipation as well as the probability of errors introduced by the measurement. Finally, we compare the delay time with the characteristic time uncertainty due to jitter (thermal fluctuations) in the JTL, and we determine how many solitons are needed for a reliable measurement.