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SUMMARY:The Coulomb drag effect induced by the third cumulant of current
DTSTART;VALUE=DATE-TIME:20190621T080000Z
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DTSTAMP;VALUE=DATE-TIME:20240809T211140Z
UID:indico-contribution-37-218@cern.ch
DESCRIPTION:Speakers: Eugene Sukhorukov (University of Geneva\, Switzerlan
d)\nThe Coulomb drag effect arises due to electron-electron interactions\,
when two metallic conductors are placed in close vicinity to each other.
It manifests itself as a charge current or voltage drop induced in one of
the conductors\, if the current flows through the second one. Often it can
be interpreted as an effect of rectification of the non-equilibrium quant
um noise of current. Here\, we investigate the Coulomb drag effect in meso
scopic electrical circuits and show that it can be mediated by classical f
luctuations of the circuit collective mode. Moreover\, by considering this
phenomenon in the context of the full counting statistics of charge trans
port we demonstrate that not only the noise power\, but also the third cum
ulant of current may contribute to the drag current. We discuss the situat
ions\, where this contribution becomes dominant.\n\nhttps://indico.unina.i
t/event/18/contributions/218/
LOCATION:Strand Hotel Terme Delfini
URL:https://indico.unina.it/event/18/contributions/218/
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SUMMARY:Full counting statistics of quantum phase slips
DTSTART;VALUE=DATE-TIME:20190621T073000Z
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UID:indico-contribution-37-219@cern.ch
DESCRIPTION:Speakers: Andrew G. Semenov (P.N.Lebedev Physical Institute)\n
In our talk we present a microscopic theory describing complete statistics
of voltage fluctuations generated by quantum phase slips (QPS) in superco
nducting nanowires. We evaluate the cumulant generating function and demon
strate that shot noise of the voltage as well as the third and all higher
voltage cumulants differ from zero only due to the presence of QPS. In the
zero-frequency limit voltage fluctuations in superconducting nanowires ar
e described by Poisson statistics just as in a number of other tunneling-l
ike problems. However\, at non-zero frequencies quantum voltage fluctuatio
ns in superconducting nanowires become much more complicated and are not a
nymore accounted for by Poisson statistics. In the case of short supercond
ucting nanowires we explicitly evaluate all finite-frequency voltage cumul
ants and establish a non-trivial relation between these cumulants and the
current-voltage characteristics of our system.\n\nhttps://indico.unina.it/
event/18/contributions/219/
LOCATION:Strand Hotel Terme Delfini
URL:https://indico.unina.it/event/18/contributions/219/
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SUMMARY:Quantum Interference in Phase Slip Devices
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UID:indico-contribution-37-238@cern.ch
DESCRIPTION:Speakers: Oleg Astafiev (National Physical Laboratory\, Teddi
ngton\, UK \, Department of Physics\, Royal Holloway University of London\
, Egham\, UK\, Moscow Institute of Physics and Technology\, Dolgoprudny\,
Russia\, Skolkovo Institute of Science and Technology\, Moscow\, Russia)\n
The Coherent Quantum Phase Slip (CQPS) effect in superconducting nanowires
is exactly dual to the Josephson effect – tunneling of Cooper pairs thr
ough a thin dielectric layer. CQPS has been experimentally proven for the
first time in Ref. [1] and since then reproduced in different materials [2
\, 3]. CQPS is interesting from the fundamental point of view as well as f
or practical applications\, particularly\, for quantum metrology as it pro
mises to build quantum current standards dual to voltage standards on the
Josephson effect. An important milestone in this direction is the demonstr
ation of interference of a pair of flux tunneling amplitudes similarly to
charge tunneling amplitudes in SQUIDs. \n We demonstrate a device exactly
dual to SQUID\, which we call a charge quantum interference device (CQUID)
[4]. The two nominally identical nanowires with constrictions separated b
y a superconducting island are fabricated to observe the quantum interfere
nce of two flux tunneling amplitudes. The effective tunneling energy depen
ds on the gate induced charge on the island. In our experiment\, the CQUID
is incorporated into a superconducting loop\, forming a phase-slip qubit
with tunable energy. Such a circuit allows to measure the CQPS energy usin
g spectroscopic methods. This is exactly dual to the charge qubit with a S
QUID\, where the effective Josephson energy is tuned by an external magnet
ic flux. \n Figure 1 demonstrates observed oscillations of energies of CQP
S qubit with two junctions (nanowires with constrictions) as a function of
gate induced charge. The oscillations are not harmonic and well described
by the interference effect of two CQPS amplitudes. \n![Energy oscillati
ons in CQUID due to interference of two tunneling amplitudes.][1]\n\n\n [
1]: https://indico.unina.it/event/18/attachments/43/175/Untitled1.png\n[1]
O. V. Astafiev\, et. al. Nature 484\, 355 (2012). \n[2] J. T. Peltonen\,
et. al. Phys. Rev. B 88\, 220506 (2013). \n[3] J. T. Peltonen\, et. al. Ph
ys. Rev. B 94\, 180508(R) (2016). \n[4] S. E. de Graaf\, et. al. Nature Ph
ysics 14\, 590 (2018).\n\nhttps://indico.unina.it/event/18/contributions/2
38/
LOCATION:Strand Hotel Terme Delfini
URL:https://indico.unina.it/event/18/contributions/238/
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