Low-frequency voltage noise in mesa-shaped stacks of intrinsic high-Tc Josephson junctions

Scherbel, J.; Mans, Michael; Schmidl, F.; Schneidewind, H.; Seidel, P.

doi:10.1016/j.physc.2003.11.006

Cited by 6 publications

(6 citation statements)

References 14 publications

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“…͑27͒, characterizing telegraph ͑diachotomous͒ noise, was observed in intrinsic LJJ. 26 We note that the noise spectrum in a small tunnel junction is described by the Lorentzian function of Eq. ͑27͒, but the 1/-like noise spectrum in a larger junction may be obtained as a result of several superimposed Lorentzian features.…”

Section: Spin-boson Modelmentioning

confidence: 97%

Decoherence in Josephson vortex quantum bits: Long-Josephson-junction approach to a two-state system

2006

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We investigated decoherence of a Josephson vortex quantum bit ͑qubit͒ in dissipative and noisy environment. As the Josephson vortex qubit ͑JVQ͒ is fabricated by using a long Josephson junction ͑LJJ͒, we use the perturbed sine-Gordon equation to describe the phase dynamics representing a two-state system and estimate the effects of quasiparticle dissipation and weakly fluctuating critical and bias currents on the relaxation time T 1 and on the dephasing time T . We show that the critical current fluctuation does not contribute to dephasing of the qubit in the lowest order approximation. Modeling the weak current variation from magnetic field fluctuations in the LJJ by using the Gaussian colored noise with long correlation time, we show that the coherence time T 2 is limited by the low frequency current noise at very low temperatures. Also, we show that a ultra-long coherence time may be obtained from the JVQ by using experimentally accessible value of physical parameters.

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Section: Spin-boson Modelmentioning

confidence: 97%

Decoherence in Josephson vortex quantum bits: Long-Josephson-junction approach to a two-state system

2006

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“…( 27), characterizing telegraph (diachotomous) noise, was observed in intrinsic LJJ. 26 We note that the noise spectrum in a small tunnel junction is described by the Lorentzian function of Eq. ( 27), but the 1/ω-like noise spectrum in a larger junction may be obtained as a result of several superimposed Lorentzian features.…”

Section: Spin-boson Modelmentioning

confidence: 99%

Decoherence in Josephson vortex quantum bits

Kim

Dhungana

Park

2007

Physica C: Superconductivity and its Applications

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We investigated decoherence of a Josephson vortex quantum bit (qubit) in dissipative and noisy environment. As the Josephson vortex qubit (JVQ) is fabricated by using a long Josephson junction (LJJ), we use the perturbed sine-Gordon equation to describe the phase dynamics representing a two-state system and estimate the effects of quasiparticle dissipation and weakly fluctuating critical and bias currents on the relaxation time T_1 and on the dephasing time T_\phi. We show that the critical current fluctuation does not contribute to dephasing of the qubit in the lowest order approximation. Modeling the weak current variation from magnetic field fluctuations in the LJJ by using the Gaussian colored noise with long correlation time, we show that the coherence time T_2 is limited by the low frequency current noise at very low temperatures. Also, we show that an ultra-long coherence time may be obtained from the JVQ by using experimentally accessible value of physical parameters.Comment: 13 pages,8 figures,to be appeared in Phys.Rev.

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“…Furthermore, TLF can also be observed due to strong quasiparticle injection. 9 Because the external quasiparticle injection into the junctions is negligible due to the sample geometry which enables superconducting feed lines to the microbridge for the bias current this explanation is improbable. The only possibility for a stronger quasiparticle injection could be given by a rather weak junction into its neighbor cluster of Josephson junction.…”

Section: Cause Considerationsmentioning

confidence: 99%

“…To prevent a high contact resistance due to the interface between the normal conductor and the superconducting top layer of the mesas circumstantial technologies are necessary, too. [6][7][8] Furthermore the quasiparticle injection through the normal contacting electrode into the mesa leads to a quasiparticle under-ground in the current-voltage characteristics, distinct lowfrequency noise due to two-level fluctuations 9 and to charge imbalance effects 10 which hobble the applicability of such devices. For whisker structures complete superconducting electrodes are possible.…”

Section: Introductionmentioning

confidence: 99%

Texture and electrical dynamics of micrometer and submicrometer bridges in misalignedTl2Ba2CaCu2O

Scherbel¹,

Mans²,

Schneidewind³

et al. 2004

Phys. Rev. B

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Different thin Tl 2 Ba 2 CaCu 2 O 8 layers were grown on 20°vicinal cut LaAlO 3 substrates by means of a two-step process. SEM pictures showed that thin film layers with a thickness smaller than 150 nm grow completely in the 20°misalignment given by the substrate but they also show few holes in the films. Thicker layers showed areas of c-axis growth beneath the expected misaligned texture whereas the allotment and numbers of c-axis islands depend on the layer thickness. TEM investigations in the selected area of misaligned growth showed a clear epitaxial relationship between the substrate and the film but they also revealed a domain like growth of the layers with plain Tl 2 Ba 2 CaCu 2 O 8 grains and stacking faults. Furthermore, the films had a rather high surface roughness depending on the layer thickness. Thin films with a thickness of 120 nm were used to pattern micro-and sub-micrometer bridges. Because of the misaligned growth and the high anisotropy of the Tl 2 Ba 2 CaCu 2 O 8 the bridges formed serial arrays of intrinsic Josephson junctions. Electrical measurements on these bridges revealed very complex dynamics within such devices. The current-voltage characteristics showed the well known branch structure of intrinsic Josephson junction arrays but with a statistical distribution of the transition currents from measurement to measurement. The temperature dependencies of the smallest critical currents generally deviated from the Ambegaokar-Baratoff theory. There was no complete suppression of the super current in an effective B-field up to 4.2 T. The analysis of the current-voltage characteristics indicated a collective transition switching especially in the first few transitions. Those could be split up by the application of a magnetic field and by the irradiation of mm-waves but not by an increment of the operation temperature. Furthermore, distinct two level fluctuations and chaotic like behavior were observed.

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Low-frequency voltage noise in mesa-shaped stacks of intrinsic high-Tc Josephson junctions

Cited by 6 publications

References 14 publications

Decoherence in Josephson vortex quantum bits: Long-Josephson-junction approach to a two-state system

Decoherence in Josephson vortex quantum bits: Long-Josephson-junction approach to a two-state system

Decoherence in Josephson vortex quantum bits

Texture and electrical dynamics of micrometer and submicrometer bridges in misalignedTl2Ba2CaCu2O

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