
\begin{center}
  {\bf \Large \textsf {High bandwidth quantum random number generators}}
\end{center}
Various quantum and classical communication schemes require a large number of
good random numbers. Homodyne measurements of optical vacuum fluctuations
serve such a purpose, and be detected with a high bandwidth.
\begin{figurehere}
  \begin{center}
    \includegraphics[width=0.4\columnwidth]{setup1}\hspace{3cm}
\raisebox{5cm}{\parbox{0.4\columnwidth} {
      \includegraphics[width=0.4\columnwidth]{extractor1}\hspace{-4cm}
      \includegraphics[width=0.35\columnwidth]{multiplot}
    }}
  \end{center}
  \figcaption{Quantum random number generation scheme based on optical
    homodyning of a vacum field $\mathsf{\ket{0}}$ with subsequent random number
    extraction. The resulting distribution is homogenous, and shows no
    correnlations in standard randomness tests.} 
\end{figurehere}
A randomness extractor based on a linear feedback shift register (LFSR) and
dropping of part of the bit sequence removes correlations in the bare digital
stream~[8].
\begin{figurehere}
  \begin{center}
\includegraphics[width=0.29\columnwidth]{new_implementation2.eps}\hspace{-1cm}
\raisebox{1cm}{\includegraphics[width=0.4\columnwidth]{qrng_compact_t.eps}}\hspace{-1.5cm}
    \includegraphics[width=0.3\columnwidth]{qrng_device.eps}
  \end{center}
  \figcaption{Compact CQT quantum random number generator prototype} 
\end{figurehere}
 Our technical implementation reaches a final random bit rate of
480\,MBit/sec, limited by the USB2 interface~[9]. A compact
device topology~[10] is currently explored for commercialization in
collaboration with an industry partner.



\begin{center}
  {\bf \Large \textsf {Stellar light sources \& Photocorrelation spectroscopy}}
\end{center}
Following up with narrowband photon pair correlation
measurements from stellar sources, we could reach another record in observed
photon bunching from stellar light sources, and exclude a major influence of
atmospheric effects on photon bunching measurements~[11].
\begin{figurehere}
  \begin{center}
\raisebox{7cm}{
  \parbox{0.45\columnwidth}{
    \includegraphics[width=0.35\columnwidth]{mnras_hbt}\vspace{1cm}
    \includegraphics[width=0.35\columnwidth]{g2sun.eps}
  }}\hspace{2cm}
     \includegraphics[width=0.35\columnwidth]{trendsun2.eps}
 
  \end{center}
  \figcaption{Photon bunching signature from sunlight, and dependency of
    elevation above horizon. The peak bunching signature seems unaffected by
    atmospheric influences.}
\end{figurehere}
Photocorrleation spectroscopy can also help determining very narrow spectral
lines found in some stellar objects. In a simulation, we are able to determine
the line width of a 20\,MHz wide spectral line on a thermal blackbody
background, an distinguish laser-like emission from pseudo-thermal light. This
may help to identify optical stellar lasers in the visible range.

\begin{figurehere}
  \begin{center}
    \includegraphics[width=0.42\columnwidth]{completesetup4}\hspace{2cm}
    \includegraphics[width=0.42\columnwidth]{g2_arclaser_6}
    % \raisebox{2cm}{\includegraphics[width=0.3\columnwidth]{blackbodysetup}} \hspace*{2cm}
    % \includegraphics[width=0.5\columnwidth]{g2_combined}
  \end{center}
  \figcaption{Left: preparation of a Doppler-widened laser line on top of a thermal
    background. Right: resultant photopair correlation, revealing a long tail
   in $\mathsf{g^{(2)}(\tau)}$ corresponding to a narrow spectral line on top
   of a thermal photon bunching signature.}
\end{figurehere}
