Posts in category Education

was bad bad bad. Me bad. I have not given this lecture for two years: Yaroslav Blanter did it. When I gave it three years ago I sort of liked it. Indeed, the topic is hot (still):qubits. Most elements of the presentation were (and are) fine, the stucture is logical  and particular topics disscussed have been worth discussing. But perhaps I’ve changed too much in these three years: I did not fit the lecture, the lecture did not fit me, and that has been accumulating.

Shamefully,  I did not explain in time what  Rabi oscillation are, although they appeared on transparencies from time to time. Moreover, when a student dared to confront me with this natural question, I a. clearly indicated I did not like the question b.instead of answering, utter a short side-story c. finally, gave clusmy, long and incomprehensive answer. Bet I looked like an ambitious fool. Just appearence: my ambitions are modest.

The main problem was that I really hated the sheets. They did not contain what I needed, instead, they contained a lot of things I did not need. In the course of the preparation I recognized the problem, and went through the set three time to find a reconciliation between me and the lecture. It looked like we reached an agreement. However, the transparencies betrayed me somehow. 

Down with the set, will never use it again. Qubits is a rapidly developing topic anyhow, the lacture must be updated.

is one of few lectures in the course where calculational flow is being combined with flow of physics: the number of variuos situations we address is significantly bigger than in most of the lectures. There are also pictures. The material is such that a good presentation seems easy. There was a little time problem before the break and in the end of the lecture, I could use several more minutes. The overal timing was however OK. More serious problem is that I am still missing rhythm of the lecture: some pieces I give too slow and some too fast. There were aslo two many blackboard drawings, many of them were extremporized. They could have been at the sheets.

I think the audience appreciated an effort I made, the attention was not lower than for other lectures. There were quite some questions, they’ve also caught me with the hbar coefficients (no, I do not intentionally put incorrect coefficients in intermediate calculations. To confess, somethimes I intentionally do not correct then: proven to sharpen student’s attention). I’ve made a dramatic statement in the end (though did not have much time for that) to prepare the audience for the coherent state: topic of the next lecture.

was similar to the second one. I have decided to change something and
one change lead to another one and so on. I have finished changing only
at 23:30. I know what price is to pay: a student has caught me on the third transparency. What belong to the denominator has unfortunately appreared in the numerator. Just two days ago my youngest son got a very bad mark for this. Fortunately, my title protects me from such cruel punisment.

But it was not that bad after all. In fact, I think it was rather good lecture and interesting one – at least for me. I shall improve on the derivation of antilocalization: there must be a simpler and more convincing way to express this. The analysis of experimental curves I guess was comprehensive, at least the students seem to follow. Or is this just my impression?

Had time problem: needed 10 minutes for weak localization. Usually I do not do such things, but my desire not to postpone the topic (it will not fit qubits anyhow) was so great that I asked the students to remain in the class for 10 more minutes. They have agreed. Thank you for this, and I won’ t to it again.

was more sucsessful than I expected. The students came in big numbers and
good mood, they were attentive and active: perhaps most have had a nice flu-less vacation. The lecture is supposed to be rather technical giving a general introduction to transitions: Fermi Golden rule, relations between emission and absorption, black-body irradiation, all that. Next lecture is supposed to provide examples, be more interesting and contain more material. This is why in the beginning I make a proposal: let’s go a bit faster, so that in the end we can eventually start with the material of eighth lecture. Not only the proposal was accepted: we really managed to do this.

There was a nice discussion around Fermi Golden Rule. It turned out that nobody knew the rule, or at least could not readily recall. Strange: former generations have had at least a vague notion of it. More improvements in bachelor education? Anyway, we manage to have really nice discussion, I guess I could bring the message about the rule, that is in odds with pure quantum mechanics but is needed to make a bridge to real world.

Another interesting discussion concerned the material of the eitht lecture.Thin emission lines, thin absorption lines: They manifest atoms. We know that our Sun consists of atoms: why its emission spectrum is continuous? Well, several years of studying physics does not automatically provide the answer, but we have manage to find one.

I enjoyed both the lecture and the audience.

was the last in the first half of the semester.  We looked at combination of Josephson junction and Coulomb blockade to understand how one can use it to make quantum devices at home. I like the topic very much and wish the students to share my feelings. I felt indeed a bit more attention from the audience than usual.

Number of things with my presentation went wrong. The introduction into home-made quantum mechanics was too hand-waving, I felt myself loosing the logics of the explanation. Though I listed the main points, they seemed rather unlinked. To circumvent this, we turn to the formulas, and here I went too formal I am afraid. Perhaps for the next time I will have to choose a more uniform style of the presentation. The beginning of the second lecture seemed OK, but I have slowly developed a time problem. As a matter of fact, I developed time problem and could not talk about arrays comprehensively.

Though I am happy I could talk about the vortices and even get some positive feedback from the audience: did not have it years past. Perhaps a student just knew what a vortex is and helped me with this. Thank you.

We agreed that we defy the vacation and meet in three weeks. Perfect.

was given in exceptional circumstances of fair weather. I could not recall this occasion for the last lecture before the semester break for all years of my service. Believe me or not, I managed to say more than I was going to. We have started with e.m. field as collection of classical oscillators, a debt from the weeks past. I gave the material in more or less reverse order: first explained the result of the activity, them the activity. Unexpectedly, this appeared to be rather convenient, and I moved reasonably fast. I wonder if the students liked it, yet they did not protest. So accelerated, we have accomplished our main task: field quantization – just before the semester break.

I expected the classical oscillators to be the most boring part of the lecture. Unfortunatelty, I was wrong. The most boring part appeared to be the last one where I talked about zero-point energy, uncertainty relations and vacuum fluctuations. I do not know why. Usually it’s rather interesting, since it goes over "fancy" subject the students have heard about but would like to hear more. Usually the audience is more interested so I also talk in more detail. Perhaps it was unwise to hurry up with this, I could have postponed the discussion till the second half of the semester. However, it’s done, and frankly I am happy to get over with.

There was an interesting discussion afterwards. The idea of a student was that the uniform mass background arising from the zero-point energy should lead to a uniform gravitational potential. So no gravitational field would have been felt. We had to write down an equation to figure out that it can not be true: the gravitational potential from a uniform mass distribution can not be uniform. Yet perhaps such reasoning is a step towards true solution of the problem?

was about Josephson effect in the context of quantum transport. Theoretically, it can be one of the best and useful lectures in the course. It combines information of general use (superconductivity, josephson relations) with something that the students can do with their "own hands", in our case, evaluate step by step, and some fascination about "unusual" processes discussed. This assumes students rady to work with "own hands" and teacher able to fascinate keeping things comprehensible and logical. To my estimation, both resourses were present but not abundant.

Right after the break we get a control question and concentrated on it. The answer has emerged, though slower than I would like it to happen. A "fascinating" introduction to superconductivity meant to provoke a discussion was listened to with attention but did not give rise to a sinlge question. Perhaps the mood was "he speaks riddles,  but may be I understand it later. In case it’s worth understanding". 

And I get to generation gap with both feet. The essence of Josephson dynamics is explained with two words: "pendulum" and "washboard". I’ve heard "washboard potential" from many young people but actually never checked if they think that Washboard is a family name of XIX century mathematician. Can somebody become a good physicist without trying to swing a pendulum with hand? Sometime ago I have tried to explain a non-linear second order differential equation to my phd student by saying "it’s like a pendulum, you know…" This did not work. Naively I thought there are some pendula left in physical practicum. It came out today that this does not seem to be the case anymore.

So let me finish this post with providing proper references for washboard

 www.nps.gov/fosc/forteachers/laundress8.htm

and pendulum (this is with equations:))

 en.wikipedia.org/wiki/Pendulum_(derivations)