Berlin 2008 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 9: Transport: Quantum Coherence and Quantum Information Systems

TT 9.2: Talk

Monday, February 25, 2008, 14:15–14:30, H 2053

Probing the States of a High-T_c Intrinsic Phase Qubit — •X. Y. Jin, J. Lisenfeld, Y. Koval, A. V. Ustinov, and P. Müller — Institut für Physik der Kondensierten Materie, Universität Erlangen-Nürnberg

We report our results on fabricating and probing high-T_c intrinsic phase qubits. An intrinsic phase qubit is a superconducting ring made of a Bi₂Sr₂CaCu₂O_8+δ single crystal, intercepted by two intrinsic Josephson junction stacks. Macroscopic quantum tunneling was observed in these qubits, and the crossover temperature was around 600 mK. An intrinsic phase qubit is generally regarded as a multi-junction system, i.e. a system of many degrees of freedom in phase space. However, we discovered that as long as the two stacks are uniform, the intrinsic phase qubits behaves like a system with only two degrees of freedom, independent of the number of junctions in the stacks. Due to the large self-inductance, the potential of an intrinsic phase qubit has several minima in which the system can stay. In order to perform quantum operations, a technique using low-frequency microwaves is developed to assure that the system stays inside the chosen potential well.