Photon energy entanglement characterization by electronic transition interference

We propose photon energy qubits and schemes for photon energy entanglement characterization. Bell inequality violation for energy qubits and complete Bell state analysis are demonstrated theoretically. Photon energy superposition state detection is performed by a two-photon absorption interferometer based on electron transition path interference. The scheme can be realized at room-temperature by two-level systems and semiconductor devices. (C) 2009 Optical Society of America