KIM FOOK LEE |
RESEARCH |
Quantum Communication and Computing using Non-Classical Light
Entanglement and superposition are foundations for the emerging field of quantum communication and information processing. These two fundamental features of quantum mechanics have made (i) quantum computation faster than any known classical computation and (ii) quantum key distribution unconditionally secure compared to communication based on classical key distribution. The main challenge of developing a new entanglement photon source is to make sure the source could provide an efficient, scalable and unconditional-ness quantum information processor. Currently, implementation of an optical quantum information system is mainly based on two types of quantum variables; discrete variable and continuous variable. They are usually generated through nonlinear interaction process in χ(2) and χ(3) media. Discrete-variable qubit based implementations using polarization and time-bin entanglement are difficult to obtain unconditional-ness, and also usually have low optical data-rate because of post-selection technique with low probability of success in a low efficient single photon detector. Continuous-variable implementations using quadrature entanglement and polarization squeezing could have high efficiency and high optical data-rate because of available high speed and efficient homodyne detection, and hence usually obtain unconditional-ness in communication and information processing. However, the quality of quadrature entanglement is very much depended on the amount of squeezing which is very sensitive to loss, so the quadrature entanglement is imperfect for implementing any entanglement based quantum protocols over long distance. Continuous-variable protocols that do not rely on entanglement, for instance, coherent-state based quantum key distribution, is perfect for long distance quantum cryptography. Coherent states have never been used to implement entanglement based quantum protocols.
Coherent state is coherent light with low mean photon number. The inherent quantum noise of coherent state could provide secure communication and bipartite entanglement in a well-designed experiment.
Quantum Communication and Computing using Non-Classical Light |
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