Single photon detector for quantum key distribution, teleportation and computing

 

As the speed of computer and storage capacity continue to increase, the network security based on mathematical encryption theories becomes more of a concern. Worst of all, the moment a functional quantum computer is developed, the current encryption system will become completely insecure immediately. Quantum cryptography, or more precisely quantum key distribution (QKD), uses the principle of quantum mechanics to assure the confidence of the key and offers the ultimate security of information transmission. Three types of devices are needed to implement a QKD system and other quantum information systems such as quantum teleportation and computing: single-photon source or entangled photon source, quantum repeater, and single-photon detector. Among these three components, single-photon detector is the most challenging one and is the key bottleneck for the realization and deployment of any quantum information systems. This presentation will focus on the theoretical and technological aspect of solid-state single photon detectors.

The specific requirements of single photon detectors include (a) operation at telecommunication wavelengths (i.e. 1310nm and 1550nm), (b) low dark count, (c) low afterpulse rate, (d) high single-photon quantum efficiency, and finally (e) number resolving capability. Semiconductor avalanche photodetectors (APDs) are considered as the most promising single-photon detectors from both device performance and practicality points of view. However, the InGaAs/InP APDs used in fiber optic communications have many shortcomings and have failed to meet the requirements for QKD application. On the other hand, Si APD photon counters have shown far superior characteristics and been used for LIDAR and other military systems that require single photon level sensitivity. In this talk we will discuss the theory and technology of combining InGaAs and Si materials to make InGaAs-on-Si single photon APDs for QKD and other quantum information systems.

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Biography of Prof. Yu-Hwa Lo

Professor Yuhwa Lo received his PhD in electrical engineering from UC Berkeley in 1987. He worked at Bellcore (now Telcordia) from 1988-1990 and at Cornell from 1991-1999 before joining UCSD. He has done research on optoelectronic devices and materials for telecommunications. His recent research efforts are focused on devices for quantum communications, microfluidics, biosensors, biophotonics, and bio-nanosystems.

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