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1 June 2005 Quantum coherent dynamics of two coupled superconducting charge qubits
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Proceedings Volume 5833, Quantum Informatics 2004; (2005)
Event: 18th International Conference on Photoelectronics and Night Vision Devices and Quantum Informatics 2004, 2004, Moscow, Russian Federation
We have analyzed and measured the quantum coherent dynamics of a circuit containing two coupled superconducting charge qubits. Each qubit is based on a Cooper pair box connected to a reservoir electrode through a Josephson junction. Two qubits are coupled electrostatically by a small island overlapping both Cooper pair boxes. Quantum state manipulation ofthe qubit circuit is done by applying non-adiabatic voltage pulses to the common gate. We read out each qubit by means of probe electrodes connected to Cooper pair boxes through high-Ohmic tunnel junctions. With such a setup the measured pulse-induced probe currents are proportional to the probability for each qubit to have an extra Cooper pai1r after the manipulation. As expected from theory and observed experimentally the measured pulse-induced current in each probe has two frequency components whose position on the frequency axis can be externally controlled. This is a result ofthe inter-qubit coupling which is also responsible for the avoided level crossing that we observed in the qubits' spectra. Our simulations show that in the absence of decoherence and with a rectangular pulse shape the system remains entangled most ofthe time reaching maximally entangled states at certain instances.
© (2005) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Yu. A. Pashkin, O. Astafiev, T. Yamamoto, Y. Nakamura, D. V. Averin, T. Tilma, F. Nori, and J. S. Tsai "Quantum coherent dynamics of two coupled superconducting charge qubits", Proc. SPIE 5833, Quantum Informatics 2004, (1 June 2005);


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