Quantop Optics Seminar by Mustafa Gündoğan – Niels Bohr Institute - University of Copenhagen

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Quantop Optics Seminar by Mustafa Gündoğan

In this talk I will summarize our experiments at ICFO towards the creation of long-lived solid-state optical quantum memories for single-photon level light fields. The optical memory is based on the atomic frequency comb (AFC) technique, which enables temporal multimode storage capability [1]. We use a praseodymium doped yttrium oxyorthosilicate (Pr3+:Y2SiO5) crystal at cryogenic temperatures. Pr3+ doped crystals have the appropriate energy levels that would allow spin-level storage and also have so far the best demonstrated properties in terms of light storage, including high efficiency [2] and long storage time of classical light [3]. 
We, first implement the full AFC scheme, where the excited state coherence is transferred to and from a spin-wave using control pulses. We achieved 5.6% efficiency, the highest reported so far [4]. Additionally, preservation of the phase in the spin states is demonstrated for the first time by performing time-bin interference experiments. Moreover temporal multimode storage capability is demonstrated by storing and recalling 5 temporal modes [4].
In order to reach quantum regime the quantum memory should operate well below 1 photon per pulse in average. However the noise created by the control pulses makes this task challenging. Sophisticated optical filtering is necessary as the relevant spin-levels lie just 10.2 MHz away from each other. Finally, I will present storage of weak coherent pulses down to 20 photons/pulse. I will then conclude by summarizing our current efforts on further decreasing the mean input photon number.

[1] M. Afzelius, C. Simon, H. de Riedmatten, and N. Gisin, Phys. Rev. A 79 (5), 052329 (2009)
[2] Georg HeinzeChristian Hubrich, and Thomas Halfmann, Phys. Rev. Lett. 111, 033601 (2013)
[3]  J. J. Longdell, E. Fraval, M. J. Sellars, and N. B. Manson,  Phys. Rev. Lett. 95, 063601 (2005)
[4] M. Gündoğan, M. Mazzera, P. M. Ledingham, M. Cristiani, and H. de Riedmatten, New J. Phys. 15 045012   (2013).