Weblog Yuli Nazarov
Quantum phase slips in superconducting wires with weak links
is the topic of another cond-mat submission today, please follow the
LINK. This is the outcome of post-doc term of Mihajlo Vanevic, who worked two last days voluntary to accomplish this submission. It was a hard project, results of which are more interesting, and – forgive me this expression – elegant then we expected in the beginning. Mihajlo does not want to stay in West anymore: he gets reseach position in Belgrado.
Here’s the abstract:
Quantum phase slips are traditionally considered in homogeneous diffusive wires. We argue that even in realistic, apparently homogeneous wires, the phase slips can occur at weak links where the local resistivity is slightly higher. We model the weak link as a general coherent conductor and obtain accurate estimate of the quantum phase-slip amplitude. We speculate on a better estimation of the amplitude for homogeneous wires as well.
Re-flows on arxiv
,finally. I’m quite proud of and excited by the paper. The excitement was so high that I’ve been working yesterday the whole day on the text, fixing small things, but, quite embarassingly, have completely forgotten to run it through a spell-checker… Oh.
Here’s the LINK.
The abstract is rather long:
We demonstrate that the condensed matter quantum systems encompassing two
reservoirs connected by a junction permit a natural definition of flows of
conserved measures, Renyi entropies. Such flows are similar to the flows of
physical conserved quantities such as charge and energy. We develop a
perturbation technique that permits efficient computation of Renyi entropy
flows and analyze second- and fourth order contributions. Second-order
approximation was shown to correspond directly to the transition events in the
system and thereby to posess a set of “intuitive” features. The analysis of
fourth-order corrections reveals a more complicated picture: the “intuitive”
relations do not hold anymore, and the corrections exhibit divergencies in
low-temperature limit manifesting an intriguing non-analytical dependence of
the flows on coupling strength in the limit of weak couplings and vanishing
temperatures.
Unphysics of quantum information
rocks. I’ve just finished my major contibution to the field: paper on flows of Renyi entropies.Will put in on cond/mat in several days.
111
My grandfather Aleksei Ivanovich Nazarov would turn 111 years old today. He has lived 82 years. I always admired the degree of change that took place in society in the course of his life span. He’s born in a poor peasant family. He and his brothers and sisters did not get any shoes till they got ten years old. He died in postindustrial society where the first personal computers just become accessible. If I project the change during my life span, I find it bigger than pleasant, yet much smaller than he has experienced. Or perhaps the projection is just wrong? Or perhaps I’m yet to see my grand(grand)children walking barefoot.
Gerwin Koolstra
made a record on Friday, 5.8.2011 by sucsessfully passing the examination in Fairly Tales of Theoretical Physics. He’s the first student ever to pass the examination!(And the first to attempt this action
.) It’s my sincere hope that he won’t be last one. We had a bunch of good motivated students during the course.
The threshold that made the examination less popular than we want is the requirement to make three problems from the home work and document the solution. This is indeed a little time investment. I believe that Gerwin Koolstra has proven that this investment pays back soon.
FQMT11
that is “Frontiers of Quantum and Mesoscopic Thermodynamics” was a relatively large conference in Prague where diverse aspects of quantum mechanics have been discussed. It has been organized (mainly) by Theo Nieuwenhuizen and Václav Špička. It’s been long I was at such broad yet interesting conference that covered everything from black holes to biomotors and I enjoyed much. Ciprian and Frans were also there. Many talks (hopefully, including mine) were inspiring and I was able to get new ideas and finish some hard calculations.
The plot of the organizers was to habituate us to everyday portion of classical music so that we get use to it, develop an addiction and will attend further conferencies in series. This has worked quite well, I must admit. Being a Slav, I could appreciate typical Slavonic hospitality that stems from the deep of the heart, may look clusmy and eccentric, yet leads to unusual and memorable experience. To give an example, we have been welcomed by His Eminence Dominique Duka, Archbishop of Prague, in his seat cathedral and were allowed to get intoxicated in Senat of Check Republic.
Many thanks, Theo and Václav, we look forward to the next conference like this.
Renyi Entropy Flows
capture my mind these days. I was busy with this research last summer, yet I still have to pack it and write down an article. There were several little things remaining to do: upon close inspection, they appear very interesting and require time investment. Next Wednesday I’ll give a talk in Prague about it.
Lesbos
is where I came from after a week of vacation with my yongest son. I’m positively charmed with the island that is still pretty wild and hardly inhabitant just in a mile or two from standard touristic places. Swinning is unpleasant and may be dangerous: yet the beaches are natural. We tramped dusty paths in hills, soaked in hot springs, broke shoes in narrow streets of traditional and less traditional villages, went to barren part of the island to venerate petrified trees and Sappho birth place…
All usual, yet natural.
Half-Josephson Laser
has finally been accepted for publication in Physical Review Letters: congratulations to Frans! The consideration took eight months.
Hans Schumacher
from Physikalisch-Technische Bundesanstalt Braunschweig, German metrology center, gave a talk today. The main direction of his research is to make a practical electric-current standard that uses electron counting in Coulomb blockade regime. Many teams, including that in Delft, have attempted this 20-15 years ago but have to stop. Hans Schumacher boldly took the road that has considered to be a dead end and has demonstrated to us a significant progress as well as a hope for even further progress. I like his strive very much and wish him best sucsess.
That was positive and encouraging part of the talk. There was also a negative and dissapoinig part. It appears that the physical factor that stopped the research 15 years ago – undesired co-tunneling processes – has been completely forgotten today. At least the speaker could not give correct esimations of the precision limitations owing to this factor, and I suspect that people helping him did not think about it too. Find this outrageous since the factor has been discussed in the literature in quite some detail and presents common knowledge in quantum transport. I suggest that the authors, invoved editors and especially anonymous referees of
Phys. Rev. Lett. 104, 186805 (2010)should immediately attend my master course in quantum transport. This seems the only way to restore the continuity of scientific progress:)