\begin{frame}\frametitle{Summary}
	\begin{block}{Remote clock synchronisation using two SPDC sources\footnote{Appl. Phys. Lett. 114, 101102 (2019)}}
	\begin{itemize}
		
		\item Independent of separation
		\item Intrinsic Clock Instabilities can be resolved
		\item Does not require trustworthy estimate of separation
		\item Secure against Symmetric Delay Attacks
		% \item Secure against symmetric attacks
	\end{itemize}
	\end{block}

	% \begin{block}{Next:\\\vspace*{+15pt}Two polarisation-entangled sources for secure~synchronisation}
	% \begin{itemize}
	% 	\item Bell test authenticates pairs
	% 	\item Open problem: Detection of asymmetric delay attacks 
	% 	% \item Sufficient brightness for tracking time-dependent offsets
	% % 	\item Improve pair rates to track frequency drifts between clocks \\
	% % 		\item \textcolor{gray}{> 100 pairs / sec for clocks with \\frequency stability of  < $10^{-8}$ over 100 ms.}
	% \end{itemize}
	% \end{block}
	\note{
	In conclusion, we have demonstrated a symmetric clock synchronisation procedure with two SPDC sources where we have measured a clock error and found it to be independent of separation.
	We also achieved a precision that allowed us to resolve fluctuations arising from the intrinsic frequency instability of each clock.
	It is secure as far as symmetric attacks are considered.

	In the next iteration, we would like to implement the same scheme with two entangled photon sources so that the origin of the pairs can be authenticated.

	It remains an open problem as to whether the presence of the optical circulators can be detected via polarization correlation measurements, or via some other methods.

	Thank you.
	% The trustworthiness of the clock error that is being estimated 
	}
\end{frame}