Poster: NMR-like experiments in superconducting quantum systems

HÉCTOR H. SEGNORILE; GÖRAN JOHANSSON; VITALY S. SHUMEIKO

Alta Gracia (Córdoba)

Congreso; Magnetic Resonance in a Cordubensis Perspective VI: New Developments in NMR; 2011

A wide variety of systems, useful for application in quantum computation (or quantum processing of the information), are available by the design of qubits using superconducting Josephson junctions1. In those devices the handling of the qubit with microwave pulses is possible. The application of those pulses permits to study decoherence in the signals generated by the qubit, which is produced by the interaction with spurious two level systems (TLS), such as parasitic electric dipoles. In that way, using different NMR-like refocusing techniques2 we can mitigate the decay of the coherences, and also we can study the properties of the TLS-qubit coupling.      Other interesting system, of recent concern, is a superconducting coplanar waveguide (CPW) resonator coupled with spins embedded in a solid state matrix, for instance a crystal doped with rare-earth’s ions3. Integrating a qubit with the resonator allows transferring of the state of the qubit to spins coupled to the resonator, thus realizing a quantum memory of the qubit state.     In this work, we present a description of the dynamic of a qubit-TLS system.     The results obtained from a simulation of the polarization, show a remarkable enhancement of the coherence time by applying a pulse sequence (see Figure 1, in poster). In addition, we study the coupling between a CPW resonator and the spins in a crystal doped with rare-earth’s ions under a semi-classical approach that permits to identify a resistive effect of the spins over the resonator circuit under the resonance condition, which is important for a perfect absorption of the microwave photons. REFERENCES: G. Wendin; and V.S. Shumeiko, arXiv:cond-mat/0508729v1, 2005. J. Bylander; S. Gustavsson; F. Yan; F. Yoshihara; K. Harrabi; G. Fitch; D. G. Cory; Y. Nakamura; J.-S. Tsai; and W. D. Oliver, arXiv:1101.4707v1, 2011. P. Bushev;  A. K. Feofanov; H. Rotzinger; I. Protopopov; J. H. Cole; G. Fischer; A. Lukashenko; and A. V. Ustinov, arXiv:1102.3841v1, 2011.