Posts in category Research

I cannot believe it myself, and it is hardly thustworthy to write about it on April 1, but please take it for a fact. I have attempted to experimentally quantify entanglement of photon pairs today. I did not do any experiments for more than thirty years.

Val Zwiller is to blame. When asked to provide an experimental setup for undegraduate lab practice, he could not come with any fresh idea. So he’s just slightly modified a setup of pioneering experiment of Alian Aspect who has quantified the violation of Bell inequality in 1981. He has invited me and Leo Kouwenhoven to "inagurate" – that’s how he put it – the experimental setup. 

At 16:00 I was at his office. We brisky got to the measurement room. On the way Val asked me with soft heartfelt tone: " Do you believe in entanglement? Do you believe in non-locality?" This gave me a thrilling impression of being a part of important rite: he sounded like a priest asking faithful about their readiness. "I do. I do believe." I responded, trying to match the tone. I wanted to add that I believe in quantum mechanics, but, given the nature of the rite (where a participant should demonstrate a ritual doubt and sucsessfully overcome it by direct measurement) this would not sound polite. 

Me and Leo have been supervised by Julia Cramer and another young lady. The setup was placed in two large plastic boxes alike my children use to store old toys. One box housed a blue laser, non-linear crystal to chop a blue photon into an entangled pair of red ones. The two go by two fibers to the second box where their polarizations have been rotated by changeable angles and finally get to photon counters. The computer gave coincidence counts, those depending on the rotation angles. The math to be made afterwards, and its significance is explained in http://en.wikipedia.org/wiki/CHSH_inequality.

There were about twenty curious people in the room, all irradiating excess heat. Val has attibuted the chaotic work of the setup to this mere circumstance. He kept re-tuning the fibers in the production box. He did it quickly and efficiently. I was turning polarizers. Leo read data and wrote it up. One needs to measure at four different positions of the polarizers. So we got 16 readings. After the experiment everybody was cheering while I had to do the math.

We did not manage to prove (our faithful devotion to ) quantum mechanics this time. This would happen if the final answer would exceed classical boundary of 2. Yet we got 1.91: Almost. Not bad for the first time.

Thanks very much, Val, Julia and all others involved: this was a wonderful and entertaining experience for me, and it will be fun for many generations of students.

has received the title of Ph.D. today. I was in the commission. His research has been in the field of electron transport at interfaces of organic materials: it is an interesting and potentially important fact that such interfaces between practically insulating materials can provide electric conduction. His research has been supervised by Alberto Morpurgo, who has been in Delft for quite some time, has made much important research here, but has left for a better position in Geneve about a year and half ago. They say he did not fit well. They did not want to promote him to a full professor. Although the story is rather old, I still feel a pity – not that much for Alberto, rather for my colleagues and Dutch society in general that has an apparent difficulty in appreciating unusual, ambitious and not-always-agreeable personalities. 

Due to this, Hangxing Xie has been working in Delft as wel in Geneve, Huub Salemink was his promotor from the Delft side. His defence performance was very tough and to the point. Beside scientific question I have addressed one of his propositions: that went about online shopping and women. I was astonished by his serious studies of the question and brisk manner of presenting every detail of this subject. 

Since Thursday I’m in Grenoble. It’s my first time over here, so I thoroughly enjoy unbelieavbly scenic views the city and its neighbourhoods have to offer. I have had already a good long hike yesterday.

But for science have I come, and that they have in abundance too. There are two large scientific centers in the city where, among other things, nanoscience activities take place. Both are thoroughly fenced off any external disturbance: the heritage of cold-war era or something else. I am visiting CEA, and have to exchange my passport for a badge with ever-worst photo of mine: the price for gaining access to their latest scientific results. On Friday my curiosity has extended to CNRS. Phyisically, it’s 200 m away. Yet there are fences too high to jump over. My host directed me to an automated gate that would let me out: naturally enough, I would not be able to get back. Yet the host was too high of opinion about my general intellegence. Finally, he had to come along and personally push all necessary buttons. It is a wonderful integrating power of science that makes the scientists of both centers aware of their mutual presence: they know each other names and, reportedly, even meet in Grenoble (by the gate?) to discuss the research, not restricting personal communications to international conferences. To finish with the topic: we’ve no (visible) fences in Delft, but surprisingly much personal communication with my colleagues takes place during international conferences.

I have talked to Julia Meyer, Manuel Houzet, Xavier Waintal – energetic, talented scientists of younger generation, and to my old friend Frank Hekking. I will remain in Grenoble for ten more days.