Spatial and Spectral mode selection of heralded single photons from Parametric Down-Conversion in bulk and PPLN

Abstract not reproduced here by request of the publisher. The text is available from: http://dx.doi.org/10.1117/12.619426

Channel models for QKD at higher photon flux levels based on spatial entanglement of twin beams in PDC

One of the key issues in QKD is the rather limited data rate at which the secret key can be generated. This paper explores the use of quantum correlation associated with twin beams in Parametric Down Conversion (PDC) to in effect create a number of parallel channels for generation of secret keys, thus significantly boosting the achievable key rate. Such quantum correlations have been effectively used as a tool for many applications, including calibration of single photon detectors and QKD applications. 1 Within QKD applications, the natural setup of quantisation of Charge Coupled Device (CCD) detection areas and subsequent measurement of the correlation statistic needed to detect the presence of the eavesdropper Eve, leads to a set of QKD parallel channel models that are either binary or multilevel Discrete Memoryless Channels (DMC). This work explores the derivation of proper channel models for this application starting from measured data and the optimization of the secret key rate. Analytical results based on measurements performed on a 30 pixel image suggest that nearly an 8-fold increase in secret key rate may be achievable using this technique

The illusionist game and hidden correlations

We suggest and demonstrate a new protocol based on correlated beams of light: the \u2018optical illusionist game\u2019. An \u2018illusionist\u2019 at first shows that if two uncorrelated light beams excited in the same Gaussian state are mixed in a beam splitter, then no correlations arise between them, as it was not present. On the other hand, when correlations with an ancillary state are exploited, the presence of the beam splitter can be unveiled