Photonic de Broglie Waves
Joseph M. Jacobson, Gunnar G. Bjork, Isaac L. Chuang, Y. Yamamoto · Physical Review Letters · 1995
In quantum optics an ensemble of photons is treated as a Bose condensate which has a de Broglie wavelength given by ${\ensuremath{\lambda}}_{0}/N$ where ${\ensuremath{\lambda}}_{0}$ and $N$ are the wavelength and average number of constituent photons, respectively. We describe an interferometer which is capable of measuring this de Broglie wavelength. We show specifically that a coherent state input has a de Broglie coherence length proportional to $1/\sqrt{N}$. Finally we show that the interferometer is Heisenberg limited in sensitivity ( $\ensuremath{\Delta}{\ensuremath{\varphi}}_{\mathrm{min}}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1/N$) and thus forms a new class of interferometers operating at the fundamental quantum limit.