Measuring the frequency-time two-photon wavefunction of narrowband entangled photons from cold atoms via stimulated emission

Abstract

Cold atom based narrowband entangled photon sources are important for efficient atom - photon interaction, which is at the heart of long-distance quantum communication and quantum memory protocols. Complete characterization of the narrowband entangled photons requires acquiring the frequency-time two-photon wavefunction, involving both joint temporal intensity (JTI) and joint temporal phase (JTP) measurements. Here, we demonstrate stimulated emission tomography of the frequency-time two-photon wavefunction of narrowband entangled photons from cold atoms. We show more than six orders of magnitude (x106) improvement in the measurement time for obtaining JTI and JTP compared to the conventional direct photon counting method, thus paving the way toward ultrafast high-resolution quantum tomography of photonic quantum states.