- Quantum Storage of Photonic Entanglement in Nd:Y 2 SiO 5 - Towards a complete AFC quantum memory in Eu:Y 2 SiO 5 Imam Usmani, Christoph Clausen, Félix Bussières, Björn Lauritzen, Nuala Timoney, Mikael Afzelius, Hugues de Riedmatten, Nicolas Sangouard, Nicolas Gisin Group of Applied Physics, University of Geneva - Switzerland

Motivation: Succesful demonstration of complete AFC memory in Pr:Y 2 SiO 5 But too few modes stored in Pr:Y 2 SiO 5 …. Solution in Eu:Y 2 SiO 5 (?)

 1/2  3/2  5/2  1/2  3/2  5/2 90 MHz 580 nm 7F07F0 5D05D0 119 MHz 194 MHz 260 MHz Eu 3+ :Y 2 SiO 5 basics Inhomogeneous absorption spectrum (10 ppm 153 Eu)  700 MHz d=1.3 - Excited state life time 2 ms - Homogeneous line width 250 Hz (T=2 K, B=0) - Max. absorption coefficient 3-4 cm -1 - Spin coherence time 15 ms for 151 Eu (B=0) 153 Eu

The 580 nm source Another advantage – nice colour for photos…

Spectroscopy

 1/2  3/2  5/2  1/2  3/2  5/2 90 MHz 7F07F0 5D05D0 119 MHz 194 MHz 260 MHz Relative transition strengths Branching ratio measurements: etc… Our choice of wavelengths

Two-level AFC echo Comb prepared on the 3/2-3/2 transition AFC-echo 2% Efficiency

… has a limited lifetime

Rabi frequency measurements Rabi frequency measurement on the 3/2-3/2 transition Rabi pulse Rabi freq = kHz

On 5/2-3/2 transition a π pulse takes 1.7 microseconds

AFC with spin wave storage in Eu:YSO 14% of the pulse area of the two level echo recovered

… inhomogeneous spin lifetime

Conclusion of second part Solid-state 580 nm laser source, 110 mW maximum power so far… Branching ratios between the 9 transitions measured, 3 transitions chosen for experiments Two-level AFC echo, albeit low efficiency (~2 %) so far, more highly doped crystals needed (multipass?,cavity?) Spin wave storage with bright input pulses. Measure the inhomogeneous spin linewidth of Eu:Y 2 SiO 5 at 36 kHz Outlook: complete AFC storage in Eu:Y 2 SiO 5 at single photon level

Nd experiments Imam Usmani (PhD) Christoph Clausen (PhD) Félix Bussières (post-doc) Eu experiments Björn Lauritzen (post-doc) Nuala Timoney (post-doc) Mikael Afzelius, Hugues de Riedmatten Nicolas Sangouard, Nicolas Gisin Thank you!