Proposed optical data link whose propagation delay is distance invariant
Gregory A. Konesky · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 2001
Recent advances in bright sources of entangled photons are combined with demonstrations of Electromagnetically Induced Transparency (EIT) to suggest a design model for an optical data link whose propagation delay is distance invariant. Intense entangled photon streams P and P' are directed into a transmitting telescope and an optical delay line respectively. The optical delay line is constructed of an extended region of EIT to reduce the local velocity of light many orders of magnitude, while experiencing no loss. A design example employing Rubidium vapor is presented. The delay line is adjusted so that as the entangled photon stream P is about to arrive at the receiver, the first photon of stream P' emerges from the delay line. A second entanglement operation on P' imposes a polarization on this photon which simultaneously appears as the compliment on the remote entangled photon of stream P. The process continues on remaining photons of both streams. An optical link budget approach is used to calculate required intensities, conversion efficiencies, apertures and received irradiances. Polarization modulation sequences are used in a transponder mode to measure the varying distance between transmitter and receiver iteratively and is used to adjust and track the optical delay line. Application to astronomical distances is considered.