Quantum dynamics of superconducting nano-circuits: phase qubit, charge qubit and rhombi chains

Buisson, Olivier; Guichard, Wiebke; Hekking, F. W. J.; Lévy, Laurent; Pannetier, B.; Dolata, R.; Zorin, A. B.; Didier, Nicolas; Fay, Aurélien; Hoskinson, Emile; Lecocq, Florent; Peng, Zhihui; Pop, I.

doi:10.1007/s11128-009-0094-0

Cited by 9 publications

(10 citation statements)

References 35 publications

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“…The existence of chiral states in the mapped arrays reflect the frustration induced by the sign-reversed two-band superconducting elements and therefore may be used has a probe of the relative phase of the superconducting gaps in TBSs. The classical behavior of the one-band rhombi chain has been experimentally observed [5,6,22] and we suggest that the results presented in this paper should also be experimentally observed in a rhombi chain with pnictide superconductors at the spinal positions if indeed a sign-reversed superconducting state occurs in these systems [20].…”

Section: Discussionsupporting

confidence: 74%

“…The JJ rhombi chain of OBSs in the high-capacitance limit has been studied in detail in Refs. [4,5,8,22]. One of the most distinct properties of the rhombi chain is the halving of the period of the supercurrent sawtoothlike profile which occurs when magnetic flux approaches half-flux quantum per rhombus plaquette.…”

Section: Symmetric Rhombi Chain Of One-band Superconductorsmentioning

confidence: 99%

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Chiral classical states in a rhombus and a rhombi chain of Josephson junctions with two-band superconducting elements

et al. 2014

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We present a study of Josephson junctions arrays with two-band superconducting elements in the highcapacitance limit. We consider two particular geometries for these arrays: a single rhombus and a rhombi chain with two-band superconducting elements at the spinal positions. We show that the rhombus shaped JJ circuit and the rhombi chain can be mapped onto a triangular JJ circuit and a JJ two-leg ladder, respectively, with zero effective magnetic flux, but with Josephson couplings that are magnetic flux dependent. If the two-band superconductors are in a sign-reversed pairing state, one observes transitions to or from chiral phase configurations in the mapped superconducting arrays when magnetic flux or temperature are varied. The phase diagram for these chiral configurations is discussed. When half-flux quantum threads each rhombus plaquette, new phase configurations of the rhombi chain appear that are characterized by the doubling of the periodicity of the energy density along the chain, with every other two-band superconductor locked in a sign-reversed state. In the case of identical Josephson couplings, the energy of these phase configurations becomes independent of the inner flux in the rhombi chain and the supercurrent along the rhombi chain is zero.

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Section: Discussionsupporting

confidence: 74%

Section: Symmetric Rhombi Chain Of One-band Superconductorsmentioning

confidence: 99%

Chiral classical states in a rhombus and a rhombi chain of Josephson junctions with two-band superconducting elements

et al. 2014

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“…At low temperatures, the junctions have critical current densities in the range of ∼ 1 µA/µm 2 . This class of Al/AlO x /Al junctions is widely used in superconducting quantum electronics 11 .…”

mentioning

confidence: 99%

Fabrication of stable and reproducible submicron tunnel junctions

Pop¹,

Fournier²,

Crozes³

et al. 2012

Journal of Vacuum Science &Amp; Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phen

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We have performed a detailed study of the time stability and reproducibility of sub-micron Al/AlOx/Al tunnel junctions, fabricated using standard double angle shadow evaporations. We have found that by aggressively cleaning the substrate before the evaporations, thus preventing any contamination of the junction, we obtained perfectly stable oxide barriers. We also present measurements on large ensembles of junctions which prove the reproducibility of the fabrication process. The measured tunnel resistance variance in large ensembles of identically fabricated junctions is in the range of only a few percents. Finally, we have studied the effect of different thermal treatments on the junction barrier. This is especially important for multiple step fabrication processes which imply annealing the junction.Sub-micron sized metal/AlO x /metal tunnel junctions are used in a wide range of applications in many fields, from superconducting and single charge electronics to calorimetry, nanomagnetism and spintronics. However, the time instability of the AlO x barrier is a frequently reported drawback. Systematic measurements of junction aging showed that the resistance of the tunnel barrier could double its value within a period of days 1 . Similarly, a reduction of the capacitance C of the junctions was also observed 2 . The junction aging is usually associated with two types of phenomena. Either (i) the diffusion of oxygen atoms from the oxide barrier to the electrodes 3 or (ii) the change of the chemical composition of the barrier, by absorption or desorption of atoms or molecules other than oxygen 4 . It has been shown that mechanism (i) plays a secondary role in the aging of the barrier, only accounting for the slow drift of the junction parameters at long time scales. Moreover, this slow diffusion of oxygen atoms can be suppressed by surface nitridation of the electrodes 5 . Mechanism (ii) is believed to play the dominant role in the aging of the junction barrier. Vacuum anneals at temperatures between 200 o C and 450 o C will accelerate the relaxation processes in the AlO x barrier and the resulting junctions show improved characteristics 1,6 .The origin of the junction contamination, which leads to the chemical relaxation in mechanism (ii), has been up to now subject of speculation. Using a standard bilayer double angle evaporation technique 7 , Koppinen et al. 1 observed a decrease in the junction aging when the substrate was cleaned with an oxygen plasma just before the electrodes evaporation. This observation suggests that the aging of the barrier is linked to the existence of resist residues in the vicinity of the junction during the deposition. Indeed, by using fabrication methods which avoid the direct contact between the photoresist and the insulating layer, it is possible to obtain perfectly stable junctions 8,9 . In the following we will show that by aggressively cleaning the substrate before the Al deposition, we could obtain perfectly stable Al/AlO x /Al junctions, using the standard bilayer double angle ev...

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“…In all these experiments, quantum measurements were based on escape or switching processes from a metastable state of a dc SQUID [68]. Quantum measurements in the Camelback phase qubit constitute a novel macroscopic quantum tunneling effect.…”

Section: Quantum Dynamics In Superconducting Circuitsmentioning

confidence: 99%

Mesoscopic electron transport and atomic gases, a review of Frank W. J. Hekking's scientific work

et al. 2018

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Quantum dynamics of superconducting nano-circuits: phase qubit, charge qubit and rhombi chains

Abstract: International audienc

Cited by 9 publications

References 35 publications

Chiral classical states in a rhombus and a rhombi chain of Josephson junctions with two-band superconducting elements

Chiral classical states in a rhombus and a rhombi chain of Josephson junctions with two-band superconducting elements

Fabrication of stable and reproducible submicron tunnel junctions

Mesoscopic electron transport and atomic gases, a review of Frank W. J. Hekking's scientific work

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