title: Temporal Purity and Quantum Interference of Single Photons from Two Independent Cold Atomic Ensembles.
abstract: The temporal purity of single photons is crucial to the indistinguishability of independent photon sources for the fundamental study of the quantum nature of light and the development of photonic technologies. Currently, the technique for single photons heralded from time-frequency entangled biphotons created in nonlinear crystals does not guarantee the temporal-quantum purity, except using spectral filtering. Nevertheless, an entirely different situation is anticipated for narrow-band biphotons with a coherence time far longer than the time resolution of a single-photon detector. Here we demonstrate temporally pure single photons with a coherence time of 100 ns, directly heralded from the time-frequency entangled biphotons generated by spontaneous four-wave mixing in cold atomic ensembles, without any supplemented filters or cavities. A near-perfect purity and indistinguishability are both verified through Hong-Ou-Mandel quantum interference using single photons from two independent cold atomic ensembles. The time-frequency entanglement provides a route to manipulate the pure temporal state of the single-photon source.
authors.affiliation: Quantum Institute of Light and Atoms, Department of Physics, East China Normal University, Shanghai 200241, People's Republic of China.
authors.forename: Peng
authors.initials: P
authors.lastname: Qian
authors.affiliation: Quantum Institute of Light and Atoms, Department of Physics, East China Normal University, Shanghai 200241, People's Republic of China.
authors.forename: Zhenjie
authors.initials: Z
authors.lastname: Gu
authors.affiliation: Quantum Institute of Light and Atoms, Department of Physics, East China Normal University, Shanghai 200241, People's Republic of China.
authors.forename: Rong
authors.initials: R
authors.lastname: Cao
authors.affiliation: Quantum Institute of Light and Atoms, Department of Physics, East China Normal University, Shanghai 200241, People's Republic of China.
authors.forename: Rong
authors.initials: R
authors.lastname: Wen
authors.affiliation: Quantum Institute of Light and Atoms, Department of Physics, East China Normal University, Shanghai 200241, People's Republic of China.|Department of Physics, Indiana University-Purdue University Indianapolis, 402 North Blackford Street, Indianapolis, Indiana 46202, USA.
authors.forename: Z Y
authors.initials: ZY
authors.lastname: Ou
authors.affiliation: Quantum Institute of Light and Atoms, Department of Physics, East China Normal University, Shanghai 200241, People's Republic of China.|Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi 030006, People's Republic of China.
authors.forename: J F
authors.initials: JF
authors.lastname: Chen
authors.affiliation: Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China.|Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi 030006, People's Republic of China.
authors.forename: Weiping
authors.initials: W
authors.lastname: Zhang