De meningen ge-uit door medewerkers en studenten van de TU Delft en de commentaren die zijn gegeven reflecteren niet perse de mening(en) van de TU Delft. De TU Delft is dan ook niet verantwoordelijk voor de inhoud van hetgeen op de TU Delft weblogs zichtbaar is. Wel vindt de TU Delft het belangrijk - en ook waarde toevoegend - dat medewerkers en studenten op deze, door de TU Delft gefaciliteerde, omgeving hun mening kunnen geven.

Posted in July 2011


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.


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:)

Exam Quantum Transport: results

I will leave for vacations soon. In order not to dissappoint the sudents with the delay of the marks, I had to check the exam papers of quantum transport quickly. I’ve worked over the weekend and finally done the job today.

The exam consisted of two parts: the problem and multiple-choice questions (mcq). Roughly, problem checks the attendance of problem-solving sessions, while mcq check if a student has re-read the lecture material before the exam:) The mcq are very accurate tool: in many cases, I can see at which lecture a student stopped re-reading of the lecture material.

The distribution of the answers to mcq was rather standart, perhaps with the maximum slightly larger than expected. However, there was a problem with the problem.

Let me explain the problem without formulas. There are two ways to solve scattering problems considered in the course. Way 1 employes summation of elementary scattering trajectories, is easy and constructive for elementary setups, but is too complicated for just a bit more complex situations. Way 2 is more formal: it requires to make a system of linear equations for amplitudes of reflected and transmitted waves that has to be solved subsequently. Both ways, the difference between them and their formal mathematical similarity have been explicitly explained in course of the lectures and problem sessions. The formulation of the exam problem clearly suggested: do it in way 2.

Oh. Vast majority of the students did it in way 1. The success to follow the way has been varying while the suffering remained rather invariant. Now I understand why the students looked so gloomy. Now it’s my turn to look so: I’ve so carefully paved way 2 to lead to examination sucsess, and almost nobody took it.

Besides a point in the problem that we regarded as ultimately trivial appeared to be an almost universal stumbling block for both strong and weak. Oh. These apparent misunderstandings made the evaluation a complicated and painful procedure. The results could be better, but, after all, they are not so bad.

© 2011 TU Delft