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.

Weblog Yuli Nazarov

Education, research and other funny things

Unveiling mysteries

with my Grenoble collaborators. Fresh submission.
How many quasiparticles can be in a superconductor?

Anton Bespalov, Manuel Houzet, Julia S. Meyer, Yuli V. Nazarov

Experimentally and mysteriously, the concentration of quasiparticles in a gapped superconductor at low temperatures always by far exceeds its equilibrium value. We study the dynamics of localized quasiparticles in superconductors with a spatially fluctuating gap edge. The competition between phonon-induced quasiparticle recombination and generation by a weak non-equilibrium agent results in an upper bound for the concentration that explains the mystery.

Sixth Lecture Advanced Quantum Mechanics 2016

was about classical stuff, representation of oscillators – rather technical and preparatory, but necessary, and, with several anecdotes, not boring.

The timing was good, though I could go faster in the first half of the lecture and slower in the second half. However, I’ve a bad feeling of not being understood completely. Perhaps next time I need to reserve time to make several simple calculations explicitly — you never know.

My question “Who does not know what vector potential is?” usually was answered positively by 20% of students. This time no single hand was risen. I wonder if the education has been improved or the question was not understood 🙂


Engineering topological materials

It’s been a while I’ve submitted something with experimentalists, yet it has happened, rather fast and unexpected. Volia!

The ω-SQUIPT: phase-engineering of Josephson topological materials

E. Strambini, S. D’Ambrosio, F. Vischi, F. S. Bergeret, Yu. V. Nazarov, F. Giazotto

Multi-terminal superconducting Josephson junctions based on the proximity effect offer the bright opportunity to tailor non trivial quantum states in nanoscale weak-links. These structures can realize exotic topologies in multidimensions as, for example, artificial topological superconductors able to support Majorana bound states, and pave the way to emerging quantum technologies and future quantum information schemes. Here, we report the first realization of a three-terminal Josephson interferometer based on a proximized nanosized weak-link. Our tunneling spectroscopy measurements reveal transitions between gapped (i.e., insulating) and gapless (i.e., conducting) states, those being controlled by the phase configuration of the three superconducting leads connected to the junction. We demonstrate the topological nature of these transitions: a gapless state necessarily occurs between two gapped states of different topological index, very much like the interface between two insulators of different topology is necessarily conducting. The topological numbers characterizing such gapped states are given by superconducting phase windings over the two loops forming the Josephson interferometer. Since these gapped states cannot be transformed to one another continuously withouth passing through a gapless condition, these are topologically protected. Our observation of the gapless state is pivotal for enabling phase engineering of more sophisticated artificial topological materials realizing Weyl points or the anomalous Josephson effect.

Tomohiro Yokoyama

has left us for further post-doc career in Japan. He stayed with me as a post-doc – eventually, a JSPS fellow, from 6.4.2014. We have worked on Andreev bound states in superconducting heterostructures, with and without spin-orbit interaction. We still have to finish a (very big) paper. Thank you, Tomohiro, with you I did the stuff I wouldn’t do otherwise. Best luck with your new job!

On blogging in general :)

I cannot blog on time. I cannot stop blogging at all: I have a feeling, most likely irrational , that the life passes by without a trace if I don’t do this. To balance between this, I’d like to use a rather dirty trick of back-dating. Please do not be surprised.

First lecture Advanced Quantum Mechanics: 2016

This year I got a very convenient lecture room, zaal E, that can house almost an infinite number of students and has a slanted floor. I gave the same course in this room yet 10 years ago. It took a bit of time to adjust: and I could enjoy again. An inconvenience is that the lectures take place on early Monday morning 🙁

Despite this, the audience was full – not unusual for the first lecture. I took time explaining the rules of the course (those I myself find rather complex). Not that I felt understood, but I said what I had to. The stuff went rather fast. Nobody has heard of Heisenberg picture, no single hand – all right, but with this it went only faster. Still I was very vague about qubits and had to skip the harmonic oscillator – too much time lost in the beginning.

I had like 4 minutes for density matrix – no preliminary knowledge as well. Looked enough, but I have discovered that the outlining of the partial trace is too abstract to be taught that quickly …

Fortunately, there was enough time on Thursday. The presentations were fine, including density matrix from thermodynamical point of view. And I told about partial trace, slowly and with details – that seemed to go into open ears. Fine!

PhD or post-doc position in theory of spin qubits in semiconducting heterostructures


In the framework of collaboration with experimental group of Lieven Vandersypen I would like to announce an opening that can be either on PhD (4 years) or post-doc (3 years) level, at the department of Quantum NanoScience at Delft University of Technology.

The successful candidate is expected to

  • have some research experience concerning theoretical spin and semiconductor physics
  • work in close and persistent interaction with experimentalists
  • be flexible with respect to short-term research planning
  • like the combination of analytical and numerical methods

The appointment can commence as early as 15-2-2016 while the starting date can be negotiated. The applications will be considered till the success of the search. The applicants are encouraged to send me their CV, motivation letters, and the list of referees. It is also very useful to make a short test and enclose the results.

Please do not hesitate to ask any questions!

Look forward to a good collaborator!

PhD position in condensed matter theory

I would like to announce a PhD opening with me at the department of Quantum NanoScience at Delft University of Technology. According to Dutch standards, this is a 4-year employment with gross salary up to 2,718 euro.

The project concerns superconducting junctions, topological effects and superconducting qubits. In its short form, it can be found here.

The preferable starting date is 1-1-2016 and can be negotiated. The applications will be considered till 10-11-2015. The applicants are encouraged to send me their CV, motivation letters, and the list of referees. It is also useful to make a test and enclose the results.

Please do not hesitate to ask any questions!

Look forward to a good collaborator!

Keldysh formalism for multiple parallel worlds

this paper with M. Ansari has appeared on arxiv today: see it here. This is our contribution to the forthcoming Special JETP issue dedicated to 85th anniversary of Prof. L. V. Keldysh.

We present here a compact and self-contained review of recently developed Keldysh formalism for multiple parallel worlds. The formalism has been applied to consistent quantum evaluation of the flows of informational quantities, in particular, to evaluation of Renyi and Shannon entropy flows. We start with the formulation of standard and extended Keldysh technique in single world in a form convenient for our presentation. We explain the use of Keldysh contours encompassing multiple parallel worlds In the end, we shortly summarize the concrete results obtained with the method.


Usually it is quite boring to write about the workshops and conferences, but not about this one. The long title is Frontiers of Quantum and Mesoscopic Thermodynamic and it was held in Prague, 27 July – 1 August 2015. The conference, as all other conferences in series, has been organized with a good care and a warm twist. Among usual things, like meeting many old friends and attending few interesting talks, my mind was rebooted by a plenty of impressions that are best described as surrealistic, almost out-of-world. Just some highlights:

– attended a concert of (well, mostly) classical musics every evening during a week

– heard the vice-president of Czech Academy of Science complaining about unjust separation of physics and musics in the structure of his establishment

– seen Gerard t’Hooft being publicly kissed by a mid-aged lady in an eye-catching garment. She had a medal for him, you see.

– listened to the same Gerard t’Hooft talking about super-determinism in gloomy theatrical environment so the cold horror of predestination grabbed my heart

– signing my book for Marlan Scully, a legend of my student times (have never met him before)

– had a too-much-wine dinner in an establishment that looked like a benedictine monastery from one side and a country-side restaurant from another side. We had a concert in their chapel, so that was the first option for sure

I could go on with the list. Many thanks to the organizers!

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