Silicon-Nitride Integrated Source of Narrowband Entangled Photon-Pairs

15 06/2015

Monday, 15 Jun. 2015, 15:00 - 16:30

Workgroup Zeilinger Group

Presenter: Sven Ramelow; Applied and Engineering Physics, Cornell University, Ithaca, USA Faculty of Physics, University of Vienna, Austria
Host: Caslav Brukner
Where: IQOQI Seminar Room, 2nd Floor, Boltzmanngasse 3, 1090 Vienna

Narrowband entangled photons are essential for future quantum communication networks based on quantum memories and become increasingly relevant for single photon cavity quantum-optomechanics. They have so far been generated with bulk cavity-enhancement or narrow spectral filtering, which entails large sizes, high complexity and stabilization requirements and thus prohibits real scalability.
Using integrated optics based on the CMOS-compatible silicon nitride platform, here we realize an ultra-compact, very bright, entangled pair source with selectable bandwidths down to 30 MHz, which is unprecedented for any fully integrated source. It is based on spontaneous four-wave mixing in fully integrated, high-Qmicroring-resonators and can generate more than 107 pairs/s with only mWs of pump power. Utilizing the intrinsic advantages of integrated Si3N4 we show robust tunability and precise wavelength stabilization. By measuring an autocorrelation of the generated photons of g(2)(0) = 2.1(1) we demonstrate their high purity and single-modeness. Moreover, as in any parametric pair source, there is time-bin entanglement, which we experimentally verify for the generated photon pairs.

a) Microscope images of high-Q Si3N4 micro-ring resonators b) principle of cavity-enhanced spontaneous four-wave mixing (SFWM) generating photon pairs in adjacent resonances from the central pump wavelength c) measured cross-correlation of the generated pairs with fitted double exponential yielding the photon’s 1/e coherence time ? and their corresponding bandwidth ??=1/(2π ?) = 30 MHz with a Q factor ??/? = 6.4 million. d) using an unbalanced interferometer time-bin entanglement results in constructive/destructive interference in the central coincidence peak with > 80% visibility.

Silicon-Nitride Integrated Source of Narrowband Entangled Photon-Pairs