Westlake News ACADEMICS

Chair Professor Alexey Kavokin received Prestigious Quantum Device Award

Xiaoqing ZHOU
19, 2020

Email: fengyi@westlake.edu.cn
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Professor Alexey Kavokin received the Quantum Devices Award for 2020 “for the prediction of room temperature Bose-Einstein condensation of exciton-polaritons, that led to the development of polariton lasers”.

Established in 2000, the Quantum Device Award annually confers scholars pioneering in the field of compound semiconductor devices and quantum nanostructure devices including physics and epitaxial growth. The award ceremony is usually held during the Compound Semiconductor Week (joint venue of ISCS and IPRM), which have either made a major scientific or technological impact in the past 20 years.

To understand the significance of polaritonics, we interviewed Professor Kavokin.


Well-deserved award


——You were awarded for your work on polaritonics. Can you tell us something about polaritons in general? What inspired you to choose the field of polaritonics in the first place?


Kavokin: Polaritonics offers an opportunity to test a wide range of physical theories in a laboratory of a millimeter size. We study processes that take place in black holes and remote galaxies by shining laser beams on small artificial crystal structures. Recently, we have studied experimentally an effect proposed 90 years ago by Erwin Schroedinger (the German Nobel prize winner, one of the fathers of quantum mechanics). Nobody could observe it before! It is very exciting to be able to discover, in a small artificial world, effects that may change the big world.


——To be more specific, you were awarded “for the prediction of room temperature Bose-Einstein condensation of exciton-polaritons, that led to the development of polariton lasers”. How can we get an understanding of what this condensation and the polariton lasers are?


Kavokin: Bose-Einstein condensation is a new phase state of matter predicted by Albert Einstein in 1924-1925 after the works of Satyendra Nath Bose from India. In this phase, a great number of quantum particles, named bosons, occupy a single quantum state. One can imagine millions of cars on a motorway that move with the same speed, accelerate and use breaks simultaneously. A Bose-Einstein condensate behaves like if it would be a single particle even if it is composed of millions of particles.

It may be formed at temperatures lower than a critical one. The effect was discovered experimentally in Li- and Rb-atoms at extremely low temperatures (about one hundred million times less than 1 °K). In the paper from 2003, we have predicted the Bose-Einstein condensation of light-matter quasiparticles named exciton-polaritons at the room temperature [1]. My co-authors of this work are prominent physicists: Guillaume Malpuech did his PhD in my former group in France, now he is a director of research at the centre national de la recherche scientifique (CNRS). Bernard Gil, who is now a director of research of an exceptional class and Honorary Professor at the Saint Petersburg State University, drew our attention to gallium nitride – a promising wide-band gap semiconductor material. Following his intuition, I initiated the research on GaN microcavities, which resulted in the breakthrough of 2007 [2]. We reported the first experimental evidence of the Bose-Einstein condensation at room temperature and demonstrated the world’s first room-temperature polariton laser. Since then, the effect was observed in many semiconductor systems.


[1]"Semiconductor microcavities: towards polariton lasers", Kavokin A, Malpuech G, Gil B, J. Nitride Semicond. Res. 8, 3, 3 (2003)

[2]"Room-temperature polariton lasing in semiconductor microcavities", Christopoulos S, von Hogersthal GBH, Grundy AJD, Lagoudakis PG, Kavokin AV, Baumberg JJ, Christmann G, Butte R, Feltin E, Carlin JF, Grandjean N, Phys. Rev. Lett. 98, 12, 126405 (2007)


——And I noticed that you emphasized this all happens at “room temperature”. Why we need room-temperature Bose-Einstein Condensate and polariton laser that you theoretically predicted and experimentally demonstrated? 


Kavokin: Before our work, it was only observed at extremely low temperatures. It was exotic physics. But now, as it is at room temperature, it comes to the everyday life. Now, polariton lasers are coming into play as important components of future quantum computers and quantum communication networks. There are thousands of research works published on this topic and tens of research laboratories are involved in studies of polaritons.

My early works on this topic were published about 20 years ago, but it takes time to confirm the theoretical prediction, demonstrate experimentally the predicted effect and develop a new generation of quantum devices – polariton lasers.Of course I was not alone doing these studies. The progress in polaritonics is a result of many years of research work of hundreds of scientists in Europe, USA, China, Russia, and Japan. 20 years of research on Bose-Einstein condensation and polariton lasing are summerized in our book “Microcavities” [3].

[3] "Microcavities”, Kavokin.A., Baumberg J.J., Malpuech G. and Laussy F.P., 2nd Edition, Oxford University Press (2017)

——You have founded an international research center for polaritonics at Westlake University. What do you want to further explore on polaritons?


Kavokin: I see two main application areas of polaritonics now:

One is for the realization of quantum computers and simulators based on semiconductor crystal structures. This is a new platform for quantum technologies that offers several significant advantages over the existing platforms. It is faster and it is expected to be flexible and cheap, compared to the superconducting platforms used by Google and IBM. Using the polariton platform, China may become a world leader in quantum computing.

Another important application area is the light-induced superconductivity. With the use of polariton condensates, we hope to be able to enhance the critical temperature of superconductivity up to the room temperature (now, it is less than -100 °C in the best cases). This would have a huge economic impact. Energy would be transferred without losses by superconducting cables.

In the next 3-5 years, we shall pursue two main goals: building the polariton platform for quantum computing and demonstrating the light-induced superconductivity. I believe, it is time to bridge the gap between the fundamental research discoveries and industrial applications. I am looking forward to establishing contacts with industrial partners in China.

Science is not all

——Interestingly,your drawings of cats appear in your seminar presentation, in many offices in your center. I heard that the next generation souvenirs of the University will have your cat as a symbol. Does your cat have a name?


Kavokin: I have published a series of books for children where the main character is Saladin, the Cat. The books have been published in various languages. I like drawing, in general; and, when I have lengthy and boring meetings, I always spend time drawing with a black pen on white paper. This is how the most part of my cats appeared.


——Can you tell us what they are about? When did you start the first book? What was your motivation? 


Kavokin: I started in 1998 when my first son Nikita was 3 years old. We were living in different countries, and to help him to learn reading I was sending him a page of a new book every day. This is how the first books about Saladin the Cat were written. This Cat likes history very much. He travels in time, visits medieval kingdoms, and solves mysteries of history. Saladin the Cat has a family: he lives in a castle together with a boy named Robin and the Grandma. They support the Cat during all of his adventures. These books are translated into many languages. My books are entertaining, but they also have an educational component. They explain complex things with simple words.

——Do your children love science? Could you give some advice to parents in general, how to inspire their children for science?


Kavokin: My first son is a scientist already. He is doing his PhD in physics in France. My other children study at school. I don’t know what they will become in the future. They like computer games, as many children do. There is a lot of science behind computer games. I hope that when they play they will be learning, too. When I am at home, I read my books to my children, and we like spending time together. When the children see that I am doing something interesting, they want to join, this is how they start learning.


——What are your hobbies? What do you enjoy doing during vacation or weekends?


Kavokin: I like reading very much. Mostly, books about history. I also like cooking, but I should not eat too much as I want to keep fit. I am doing some sports when I have time: cycling, swimming, mountain skiing. And I like drawing, writing stories, and playing board games.


We look forward to Professor Kavokin leading the international research center for polaritonics at Westlake University to further achievements. The labs will be fully functional soon. We also cannot wait to see the Cats on Westlake University souvenirs and his books for children about quantum computers and racing cars.