Président du jury Cerf, Nicolas
Promoteur Phan Huy, Kien
;Merolla, Jean-Marc ;Emplit, Philippe ;Massar, Serge Publication Non publié, 2014-12-19
| Résumé : | In the twentieth century, the founding fathers of quantum mechanics explored the implications of their theory by designing gedanken experiments. In recent years, continuous improvement of the experimental manipulation of individual quantum systems has opened the way to exciting research, both on blackboards and in laboratories, and even towards field experiments. The manipulation of individual quantum systems is the basis for quantum information processing: when an information content is associated with transformations and measurements of quantum systems, it offers a new paradigm, full of potentialities, to information theory. This leads to quantum random number generation, quantum computing, quantum communication, including quantum teleportation and quantum cryptography, etc. One of the promises of quantum information is the realization of a quantum internet: quantum communication links would allow to share quantum states between the nodes (quantum computers) of the network. Our work lies in the context of experimental quantum optics in optical fibers at telecommunication wavelengths, in view of quantum communication applications. More particularly, we study photon pairs entangled in their energy-time degree of freedom. The traditional approach to manipulate energy-time entangled photons is based on the notion of time bin: quantum information is encoded in the relative phase between distinct spatio-temporal paths, which interfere via Mach-Zehnder interferometers. The aim of our work is to demonstrate an alternative approach to manipulate energy-time entangled photons in optical fibers at telecommunication wavelengths. We investigate and implement an original method for their manipulation by building on proven techniques for their production, transmission and detection (namely nonlinear waveguides, optical fibers and single-photon detectors, respectively). The photon pairs produced by a parametric down-conversion source are sent through independent electro-optic phase modulators, which act as high-dimensional frequency beam splitters, transforming the photonic states in the frequency domain. We then use frequency filters to discriminate the photons' frequencies. Such experimental methods, whose classical origin can be traced back to coherent communication, have been previously used with attenuated coherent states as approximations of single photons. In the present work, we aim to show that frequency-bin entanglement provides an interesting alternative platform for quantum communication. Our main experimental results towards this goal are the obtaining of high-visibility two-photon interference patterns allowing Bell inequality violations. Our method provides decisive advantages: high dimensionality, use of standard optical and optoelectronic components, inherent stability and robustness, no need for active stabilization in laboratory conditions, visibilities comparable to the highest obtained using other degrees of freedom, etc. It has however a few drawbacks, mainly high losses and the somewhat complexity of the radio-frequency system which is not standard in quantum optics. Exploiting the high dimensionality is also challenging. Overall, our method allows the implementation of traditional and original quantum optics experiments with interesting perspectives for quantum information and communication. |
