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His work on "High-performance single-photon detectors and applications in quantum communication", under the direction of Prof. Hugo Zbinden, has received the J. Wurth Award, which rewards the best PhD thesis in physics.

Every year, the physics Faculty of the University of Geneva rewards the best PhD thesis in physics with the J. Wurth Award. The decision has been officially taken in November.

Official website:

http://cms.unige.ch/sciences/physique/la-section/p...

His thesis is available here:

http://archive-ouverte.unige.ch/unige:88979

Abstract:

During this thesis two approaches to single-photon detection at telecom wavelengths have been investigated, using semiconductor and superconductor technologies. On the application side, quantum key distribution (QKD) was implemented. In the first part of the thesis I studied the operation of free-running InGaAs/InP negative feedback avalanche diodes (NFADs). Through extensive study of the low temperature behavior of these detectors, insights into the fundamental characteristics such as the efficiency, dark count rate (DCR), afterpulsing and jitter, were found. The key finding is that these detectors can operate with an extremely low dark count rate, which opens up a host of new applications. The second part of the thesis concentrated on the development, fabrication and characterization of superconducting nanowire single-photon detectors (SNSPDs). These detectors are highly attractive because they can achieve excellent attributes simultaneously, such as high efficiency, low noise, good temporal resolution, no afterpulsing and high count rates. The main attribute of the developed devices is the material of choice, being amorphous MoSi. This is a relatively new material to be used for SNSPDs and shows great promise due to its highly uniform nature, which yields good fabrication yields and favorable attributes such as saturated internal efficiency. The final part of the thesis looks at the application of these detectors to QKD. It is demonstrated that the use of NFADs can enable record distance QKD over 307 km of optical fiber. Crucially, this experiment is the first long distance QKD demonstration which could provide a quantitative measure of the security parameter. Finally, a proposal and numerical analysis of a QKD experiment which can further improve the performance of QKD through the use of SNSPDs, is outlined. In particular two scenarios are analyzed, namely long distance operation which could extend the record distance by an additional 100 km and high rate operation which could increase the state-of-the-art secret key rate by over an order of magnitude.


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