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Posted in December 2009

Quantum NanoScience

rules and ,as rumour has, will become an official name of our department from January 1st. In principle, I like the name: it adequately reflects ambitions, arrogance and to put it frankly, certain callowness of our team. My only concern is that this name would provoke jokes. If you think you can make a good joke using this name, please do not hesitate to put it here as a comment: I am sure we can find means to award the winner!

Superconducting spin qubits

are best qubits ever combining natural representation of two-level system in terms of electron spin with all advantages of superconducting qubits. This is discussed in our paper with Ciprian Padurariu submitted on cond-mat today. You will see it on Monday at

For Ciprian, this is the first submission. It was difficult to work on the text, especially in last days. Anyway, we’ve this job done.

Phase-slip oscillator: few-photon non-linearities

is a fascinating proposal of a superconducting device where phase-slips, topological instantons of superconducting order parameter, influence driven oscillations in a resonator.
If you are in resonance of any kind, and Lorentian shape of it have already become a boring habit for you, you must see our paper. As a matter of fact, we make a fascinating corkscrew out of the Lorentian, this promises some interesting applications. Read it tomorrow at

This is the first submission of Alina Hriscu, my PhD student. To make it done, we had to work against the clock for last several days. I hope that she still catches her plane in the evening.

Katja Carola Nowack

has been promoted in Delft yesterday. She has been student of Lieven Vandersypen and got several spectacular accomplisments in the field of spin qubits. She’s got this doctor title with cum laude. Despite being accomplished scientist, Katja is very pleasant person and reliable collaborator. We have co-authored three publications. Besides, Katja is my scientific grandchild: she graduated in Aken in theoretical physics, and my former student has supervised her diploma thesis.

Naturally, I was in her promotion commission. Katja is a sharp and quick thinker, it was a pleasure to see how she answered questions, even those without an answer. My secret pleasure was that nobody in the commission has adressed her rather provocative proposition number 8. Katja sometimes has very strong opinions. While I respect her right for that I was afraid that public discussion of this proposition would make me nauseatic …

Twelfth lecture aqvanced quantum mechanics

was a detour to relativistic world, a world which is not completely detached from ours. Yet it has special (relativity) rules, it has a special look and feel: in full accordance with pre-Chirstmas feelings we all have. We talk about Minkowski and his sudden death, we’ve derived plenties of physical laws from Lorentz invariance, got quantum-mechanical and reached Dirac equation. We have second-quantized it and filled Dirac cellar with electrons. That’s it, we would be able to proceed with quantum electrodymanics if it was an intention of the course.

The relativistic mechanics is the most ancient part of the course. At some stage I wanted to scrap it for the sake of more practical things but I was stopped by more practical colleagues who remembered a pre-Christmas feeling of the topic. So I use to gave it.

That has been the last lecture, and I have to say good-bye to the course. I will not read it at least for a number of years. Will miss it. Thanks to all students attending!

Anyway the semester is over, I could enjoy this if I did not have to finish some papers before Christmas… No time to relax yet.

Fully overheated single-electron transistor

this work in collaboration with my Finnish colleagues Matti Laakso and Tero will appear tomorrow at
We looked at one of the most studied nanodevices, SE transistor. To our surprise, we have discovered a set of new effects related to temperature fluctations in the device core while it is overheated. Those are reflected in the current through the device.

There is a detail of special significance for me. I got to Delft for the first time about twenty years ago and talk to experimentalists, Bart Geerligs and Hans Mooij. They listed questions I could help them with. One was a little puzzle with freshly observed co-tunneling transport. There was a factor of two discrepancy between experiment and theory. It looks like finally we managed to resolve this puzzle: overheating must be the reason.

Concluding nolecture quantum transport

was an attempt to summarize the course read in a less formal manner. So I started with blackboard presentation about powers of ten, Epicurus, nanoscience and, of course, the conductance quantum. I sketched all the field in a two-axis plot. Upon request, gave a list of lectures. Explained the exam and even advertised the groups related to quantum transport.

Then the students asked questions. Frankly, I expected more. I got just two from the same student: so he got an extra point for examination without much of competition.

That was it for this year. Ciprian will give the problem-solving session and we will begin to think about the examination.

Eleventh lectrure advanced quantum mechanics

went surprisingly smooth despite the fact it was the last and most difficult lecture in the course. Or at least I managed to do it better than in years past. The pace was unform during the whole lecture, I could have been on time: just was slow during last three minutes so I had to take a minute of students time, sorry for that. There were questions, although I did not really provoked those. I mentioned several times my emotional envolvment with the topic.

So I enjoyed, and it’s a pity that I will not give this lecture at least for a number of years. I will miss it. There’s a new geneal policy taken from Germany that a professor should not give a course for too long. So I will swap the courses with Jos Thijssen and will give Advanced Statistical Mechanics starting winter 2011. Still have to figure out how mechanics could be statistical.

Job Cohen in orthodox parish

So the rumour had it right: Job Cohen has visited our parish. There’s the official press-release:
“To begin the celebration of its 35th anniversary, on 4 Decemeber 2009 the parish of St. Nicolas of Myra in Amsterdam hosted a symposium on the role of the Russian Orthodox parish in the city of Amsterdam. Participants included Mayor Job Cohen, journalist Hubert Smeets (during part of his career he was based in Moscow), Jurjen Beumer, director of “Stem in de Stad” (Voice in the City) in Haarlem, and Archimandrite Meletious Webber, abbot of St. John of Shanghai Monastery in California, who formerly was a guest priest assisting the Amsterdam parish.”

You can find an excellent foto-set, a must-see for all PvDA’ers and Orhodox, at

Spin-dependent boundary conditions for isotropic superconducting Green’s functions

is quite a long title. From the other hand, the paper is also quite long. Click here to have a look.

As to research, it took more than eight years to accomplish the project. We have started it with my that time phd student Daniel Huertas-Hernando in hope to complete it quickly. However, it did not want to go that way. Wolfgang Belzig has helped us so we got a preliminary write-up in april 2002. Wolfgang has become a professor, moved to Konstanz, was having students: finally, his that time student Audrey Cottet took a banner from the hands of fallen. Without her persistance we’ve never been done.

So it’s all about spintronics and superconductors…

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