Dresden 2003 – wissenschaftliches Programm
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SYQD: Quantum decoherence in solid state physics
SYQD 1: Quantum Decoherence in Solid State Physics I
SYQD 1.2: Hauptvortrag
Dienstag, 25. März 2003, 14:30–15:00, HSZ/01
Decoherence and 1/f Noise in Josephson Qubits — •Elisabetta Paladino1,2, L, Faoro3, A. D’Arrigo1, Rosario Fazio2,4, and G. Falci1 — 1Dipartimento di Metodologie Fisiche e Chimiche (DMFCI), Università di Catania,viale A. Doria 6, 95125 Catania, Italy — 2NEST-INMF & Scuola Normale Superiore, Pisa , Italy — 3Institute for Scientific Interchange (ISI), Viale Settimo Severo 65, 10133 Torino, & INFM, Unità del Politecnico di Torino, Italy — 4Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa, Italy
A high degree of quantum coherence is a crucial requirement for the implementation of quantum logic devices. Solid state nanodevices appear to be suited for large scale integrability and flexibility in the design, but suffer from decoherence due to the presence of many low energy excitations in the environment. In particular 1/f noise is a severe problem.
Here we study the decoherence due to an environment of bistable quantum fluctuators [1], thus modeling the decoherence in Josephson qubits induced by fluctuating background charges located close to the device. This environment has a discrete character and a very large low-frequency density of excitations. As a consequence it displays different physics for different kind of operations of the qubit. We performed a detailed investigation of various computation procedures (single shot measurements, repeated measurements), with no need of ad hoc assumptions about the low frequency cutoff of the 1/f noise. Although, in general, information beyond the power spectrum is needed, in many situations the knowledge of only one more microscopic parameter of the environment is sufficient. This allows us to determine which background charges are effective sources of decoherence in each different physical situation considered.
[1] E. Paladino, L. Faoro, G. Falci, and R. Fazio, Phys. Rev. Lett. 88, 228304 (2002).