Supercurrent decay in extremely underdamped Josephson junctions

Ruggiero, B.; Granata, C.; Palmieri, V.G.; Esposito, Aniello; Russo, M.; Silvestrini, P.

doi:10.1103/physrevb.57.134

Cited by 29 publications

(16 citation statements)

References 17 publications

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“…Thermal activation in a current biased Josephson junction has been studied both theoretically and experimentally for large damping 7,8 , intermediate to low damping 9,10,11 and extremely low damping 11,12 . At low temperatures the quantum mechanical properties of Josephson junctions have been investigated in relation to macroscopic quantum tunneling (MQT) 13,14,15 , energy level quantization (ELQ) 12,16 and macroscopic quantum coherence (MQC) 17 .…”

Section: Introductionmentioning

confidence: 99%

Switching current measurements of large area Josephson tunnel junctions

Wallraff

Lukashenko

Coqui

et al. 2003

Review of Scientific Instruments

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We have developed a scheme for a high resolution measurement of the switching current distribution of a current biased Josephson tunnel junction using a timing technique. The measurement setup is implemented such that the digital control and read-out electronics are optically decoupled from the analog bias electronics attached to the sample. We have successfully used this technique to measure the thermal activation and the macroscopic quantum tunneling of the phase in a small Josephson tunnel junction with a high experimental resolution. This technique may be employed to characterize current-biased Josephson tunnel junctions for applications in quantum information processing.

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Section: Introductionmentioning

confidence: 99%

Switching current measurements of large area Josephson tunnel junctions

Wallraff

Lukashenko

Coqui

et al. 2003

Review of Scientific Instruments

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“…The prefactor At depends on the damping 11 related, within the RSJ model, to a junction "effective" resistance R and capacitance C (11-R~ ) [3,14]. In 1 underdamped junctions «roRCr «1), At is responsible for two different damping regimes: the transition rate regime (TR) with At almost independent of 11, and the extremely low damping regime (LD) with At proportional to 11 [12,14,16].…”

Section: Theoretical Backgroundmentioning

confidence: 99%

Macroscopic Quantum Phenomena in Underdamped Josephson Junctions

Corato

Esposito

Granata

et al. 2001

Macroscopic Quantum Coherence and Quantum Computing

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We present an experimental study of the supercurrent decay in extremely underdamped Josephson junctions. In the thermal regime, we present data on the rate of escape from the supercurrent state as function of the external energy both in quasi-stationary and non-stationary conditions for the system. We evaluate the relevant junction parameters and the effective dissipation and we get experimental evidence of energy level quantization at temperatures well above the classical-quantum crossover one. In the quantum limit we show results on macroscopic quantum tunneling in different extremely underdamped Josephson junctions. All measurements employ low noise electronics, as well as different techniques to reduce the effective dissipation by filtering the lines wiring the junction. The extremely low value of dissipation obtained in the observation of incoherent effects in underdamped Josephson junctions, is encouraging in view of experiments of coherent tunneling between energy levels in an rf-squid system.

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“…3b shows the experimental dependence of the switching current distributions from the zero voltage state P(I) and the related escape rates Γ, as a function of the bias current I, at different temperatures measured using the standard fly technique [4,10] Theoretical curves are obtained using the thermal theory in the moderately damping limit. The fitting parameters are C=1 fF, I c0 =506 µA, R=50 Ω, Q=ω p RC=2 and T=4.2 K. As it is evident in Fig 3, the theoretical predictions are in good agreement with the experimental data indicating that the escape process from the metastable state in these devices can be reasonably described in the framework of a thermal theory in the moderately damping limit (Q≥1) [11].…”

Section: Supercurrent Decay Measurementsmentioning

confidence: 99%

NANO-SQUIDs based on niobium Dayem bridges for nanoscale applications

Granata

Vettoliere

Walke

et al. 2010

J. Phys.: Conf. Ser.

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Abstract. We report on the design, the fabrication and the performance of an integrated magnetic nano-sensor based on niobium dc-SQUID (Superconducting QUantum Interference Device) for nanoscale applications is presented. The nano-sensors are based on nanometric niobium constrictions (Dayem bridges) inserted in a square loop having a side length of 200 nm. Measurements of voltage-flux characteristic, flux to voltage transfer factor and noise performances are reported. In small signal mode, the sensors have shown a magnetic flux noise spectral density of 1.5 µΦ 0 /Hz 1/2 corresponding to a spin sensitivity in unit of Bohr magneton of 60 spin/Hz 1/2 . Supercurrent decay measurements of these devices are also reported. Such measurements provide useful information for applications which employ the SQUID as a trigger where the sensor works on the zero voltage state. The experimental data, have shown an intrinsic current fluctuation less than 0.2% of the critical current at liquid helium temperature, corresponding to an intrinsic sensor magnetic flux resolution of a few mΦ 0 . In view of the nano-SQUID employments in the detection of small spin populations, the authors calculated the spin sensitivity and the magnetic response relative to the single spin, as a function of its position within the SQUID hole. The results show that the SQUID response depends strongly on the spin position.

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Supercurrent decay in extremely underdamped Josephson junctions

Cited by 29 publications

References 17 publications

Switching current measurements of large area Josephson tunnel junctions

Switching current measurements of large area Josephson tunnel junctions

Macroscopic Quantum Phenomena in Underdamped Josephson Junctions

NANO-SQUIDs based on niobium Dayem bridges for nanoscale applications

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