title: Two-photon interference of weak coherent laser pulses recalled from separate solid-state quantum memories.
abstract: Quantum memories allowing reversible transfer of quantum states between light and matter are central to quantum repeaters, quantum networks and linear optics quantum computing. Significant progress regarding the faithful transfer of quantum information has been reported in recent years. However, none of these demonstrations confirm that the re-emitted photons remain suitable for two-photon interference measurements, such as C-NOT gates and Bell-state measurements, which constitute another key ingredient for all aforementioned applications. Here, using pairs of laser pulses at the single-photon level, we demonstrate two-photon interference and Bell-state measurements after either none, one or both pulses have been reversibly mapped to separate thulium-doped lithium niobate waveguides. As the interference is always near the theoretical maximum, we conclude that our solid-state quantum memories, in addition to faithfully mapping quantum information, also preserve the entire photonic wavefunction. Hence, our memories are generally suitable for future applications of quantum information processing that require two-photon interference.
authors.affiliation: Institute for Quantum Science and Technology, Department of Physics & Astronomy, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada.
authors.forename: Jeongwan
authors.initials: J
authors.lastname: Jin
authors.forename: Joshua A
authors.initials: JA
authors.lastname: Slater
authors.forename: Erhan
authors.initials: E
authors.lastname: Saglamyurek
authors.forename: Neil
authors.initials: N
authors.lastname: Sinclair
authors.forename: Mathew
authors.initials: M
authors.lastname: George
authors.forename: Raimund
authors.initials: R
authors.lastname: Ricken
authors.forename: Daniel
authors.initials: D
authors.lastname: Oblak
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Sohler
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Tittel