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.
His thesis is available here:
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.