Quantum decay rates for dissipative systems at finite temperatures

Grabert, Hermann; Olschowski, Peter; Weiß, Ulrich

doi:10.1103/physrevb.36.1931

Cited by 236 publications

(206 citation statements)

References 53 publications

Supporting

Mentioning

193

Contrasting

Order By: Relevance

“…2 show that, in both the thermal (T > 2T co ) and quantum (T > T co =2) regimes, the distributions, including their shape, width, and position, agree very well with the theoretical predictions. Below 0.15 K the data were essentially the same, as expected for a system with very low damping [17,18]. Tunneling rates obtained from the switching current distributions are plotted as a function of barrier height in Fig.…”

Section: Volume 89 Number 9 P H Y S I C a L R E V I E W L E T T E R mentioning

confidence: 61%

“…2(b), in the crossover region the measured distributions deviate significantly from that of T 0 MQT theory (the dashed line). By taking into account the effects of thermal enhancement to MQT [17], the agreement between the data and theory (the solid line) improves. However, the remaining disagreement cannot be entirely accounted by the thermally enhanced MQT theory, indicating the need for further studies in this temperature range, where neither TA nor MQT is the dominant escape mechanism.…”

Section: Volume 89 Number 9 P H Y S I C a L R E V I E W L E T T E R mentioning

confidence: 76%

“…One mechanism that could result in a larger width is the thermal enhancement of MQT, which produces an improved, albeit still unsatisfactory, agreement with the data for 0:15 K < T < T co . For T co < T < 0:6 K, the theory of quantum correction [17] produced negligible improvement. In the crossover region, the shape of P x also significantly deviates from that calculated from Eq.…”

Section: Volume 89 Number 9 P H Y S I C a L R E V I E W L E T T E R mentioning

confidence: 99%

“…In our experiment, the capacitance of the dc SQUID, C 2C J 380 30 fF, was determined from resonant activation (RA) measurement [15] at 4.2 K. The RA data also yielded a quality factor, Q RC! 0 200, indicating that the effect of damping on tunneling at T T co was negligible [17,18]. The inductance of the dc SQUID loop, estimated from the modulation depth of critical current and loop geometry, is L 5 1 pH.…”

mentioning

confidence: 99%

See 3 more Smart Citations

Quantitative Study of Macroscopic Quantum Tunneling in a dc SQUID: A System with Two Degrees of Freedom

et al. 2002

Phys. Rev. Lett.

View full text Add to dashboard Cite

To test whether the theory of macroscopic quantum tunneling (MQT) is applicable to systems with 2 degrees of freedom, we experimentally investigated the switching current distribution of a dc SQUID. Using sample parameters determined from measurements at T 4:2 K, we are able to make quantitative comparison to the theories from 8 mK to 4.2 K. The excellent agreement between the data and the MQT theory demonstrates that tunneling from the zero-voltage state of the dc SQUID is well described by the quantum mechanics. DOI: 10.1103/PhysRevLett.89.098301 PACS numbers: 85.25.Dq, 03.65.-w, 74.50.+r Whether quantum mechanics is valid for macroscopic variables is one of the most fascinating issues of fundamental physics [1]. The experimental studies, especially quantitative tests of the theory for macroscopic variables in the quantum regime, provide important insights to our understanding of the physical world. In the past few years, devices based on the Josephson effect, such as the Josephson junction (JJ) and the superconducting quantum interference device (SQUID), have been proven effective systems to perform this test. For instance, in a JJ, the phase difference across the junction is a macroscopic variable and the dynamics of the junction is identical to a particle's motion in a one-dimensional (1D) washboard potential. Experiments in 1D systems, such as current biased JJs and rf SQUIDs, have yielded results in very good agreement with the theoretical predictions of macroscopic quantum tunneling (MQT) [2][3][4][5][6]. In contrast, experiments in systems with 2 degrees of freedom (2DF) have produced significant divergences. For example, using a dc SQUID, which contains two JJs and, hence, has two macroscopic degrees of freedom, Sharifi, Gavilano, and Harlingen (SGH) reported the observation of anomalous suppression of thermal activation (TA) from the two-dimensional (2D) potential well of a dc SQUID [7]. SGH suggested that the apparent suppression of TA rate may rise from an enhanced potential barrier caused by interaction between the two macroscopic degrees of freedom in the dc SQUID. On the other hand, experiments by Han, Lapointe, and Lukens (HLL) [8] and Lefevre-Seguin, Turlot, Urbina, Esteve, and Devoret (LTUED) [9] showed that, in the thermal regime, the activation energy of the 2D SQUIDs agreed very well with the potential barrier. More importantly, SGH's result in the quantum regime significantly disagreed with the theoretical prediction as the measured width of switching current distribution-at temperature well below the quantum-classical crossover temperature T co ÿ exceeded the theoretical prediction by more than 40%.Notice that this disagreement could not be accounted for by measurement uncertainties and the barrier enhancement suggested by SGH would actually make the matter much worse. However, the HLL and LTUED's experiments did not address the quantum regime so that the experimental evidence available thus far [7] seems to indicate that, despite its great success in describing 1D systems, MQT theory...

show abstract

Section: Volume 89 Number 9 P H Y S I C a L R E V I E W L E T T E R mentioning

confidence: 61%

Section: Volume 89 Number 9 P H Y S I C a L R E V I E W L E T T E R mentioning

confidence: 76%

Section: Volume 89 Number 9 P H Y S I C a L R E V I E W L E T T E R mentioning

confidence: 99%

mentioning

confidence: 99%

See 2 more Smart Citations

Quantitative Study of Macroscopic Quantum Tunneling in a dc SQUID: A System with Two Degrees of Freedom

et al. 2002

Phys. Rev. Lett.

View full text Add to dashboard Cite

show abstract

“…The MQT rate Γ can be calculated in the standard way [12,13] from the imaginary part of the free energy F , i.e.,…”

mentioning

confidence: 99%

How to Detect the Fourth-Order Cumulant of Electrical Noise

Ankerhold

Grabert

2005

Phys. Rev. Lett.

Self Cite

View full text Add to dashboard Cite

It is proposed to measure the current noise generated in a mesoscopic conductor by macroscopic quantum tunneling (MQT) in a current biased Josephson junction placed in parallel to the conductor. The theoretical description of this set-up takes into account the complete dynamics of detector and noise source. Explicit results are given for the specific case of current fluctuations in an oxide layer tunnel junction, and it is shown how the device allows to extract the fourth order cumulant of the noise from the MQT data for realistic experimental parameters. PACS numbers: 72.70.+m,74.50.+r, Within the last decade electrical noise has moved into the focus of research activities on electronic transport in nanostructures [1], since it provides information on microscopic mechanisms of the transport not available from the voltage dependence of the average current. Lately, attention has turned from the noise auto-correlation function to higher order cumulants of the current fluctuations characterizing non-Gaussian statistics [2,3]. While theoretical attempts to predict these cumulants for a variety of devices are quite numerous [3], experimental observation is hard because of small signals, large bandwidth detection, and strict filtering demands. A first pioneering measurement by Reulet et al. [4] of the third cumulant of the current noise from a tunnel junction has intensified efforts and several new proposals for experimental setups have been put forward very recently, some of which are based on Josephson junctions (JJ) as noise detectors. Lindell et al.[5] employed a Coulomb blockaded JJ to demonstrate that the conductance of the junction in the Coulomb gap region is sensitive to the non-Gaussian character of noise applied to the junction. A modification of this set-up was suggested by Heikkilä et al.[6] to get specific information on the third cumulant of the noise. Another recent experiment [7] has observed activatedover-the-barrier-jumps of a JJ biased by a noisy current. The data are consistent with resonant activation produced by the second cumulant of the noise at the plasma frequency of the junction. For a measurement of the full distribution of current fluctuations Tobiska and Nazarov [8] suggested to use an array of overdamped JJs acting as a threshold detector for rare current fluctuations triggering over-the-barrier jumps. Since in the overdamped limit retrapping spoils the built-up of a detectable voltage, it was argued by Pekola [9] that an experimentally more accessible detector would extract the noise characteristics from modifications of the macroscopic quantum tunneling (MQT) rate in an underdamped JJ.In all experimental set-ups to measure higher order cumulants realized and proposed so far, heating is one of the major experimental obstacles [10]. Thus, experiments have primarily attempted to establish just the unspecified non-Gaussian nature of the noise or to measure the third cumulant (skewness). The latter one is particularly accessible since it can be discriminated from purely Gaussian noise due...

show abstract

References

1994

Advances in Chemical Physics

View full text Add to dashboard Cite

Quantum decay rates for dissipative systems at finite temperatures

Cited by 236 publications

References 53 publications

Quantitative Study of Macroscopic Quantum Tunneling in a dc SQUID: A System with Two Degrees of Freedom

Quantitative Study of Macroscopic Quantum Tunneling in a dc SQUID: A System with Two Degrees of Freedom

How to Detect the Fourth-Order Cumulant of Electrical Noise

References

Contact Info

Product

Resources

About