We propose to perform quantum key distribution using quantum correlations
occurring within thermal states produced by low power sources such as LED's.
These correlations are exploited through the Hanbury Brown and Twiss effect. We
build an optical central broadcast protocol using a superluminescent diode
which allows switching between laser and thermal regimes, enabling us to
provide experimental key rates in both regimes. We provide a theoretical
analysis and show that quantum secrecy is possible, even in high noise
situations.Comment: This version includes revisions prompted by referees comments, and
some other small editorial comment
