- Quantum Storage of Photonic Entanglement in Nd:Y2SiO5

- Towards a complete AFC quantum memory in Eu:Y2SiO5

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:Y2SiO5

But too few modes stored in Pr:Y2SiO5 ….

Solution in Eu:Y2SiO5

(?)

1/23/2

5/2

1/2

3/2

5/2

90 MHz

580

nm

7F0

5D0

119 MHz

194 MHz

260 MHz

Eu3+:Y2SiO5 basics

-2000 -1000 0 1000 20000

0.2

0.4

0.6

0.8

Frequency (MHz)

Tra

nsm

itted

inte

nsity

Inhomogeneous absorption spectrum(10 ppm 153Eu)

700 MHzd=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 151Eu (B=0)

153Eu

The 580 nm source

Another advantage – nice colour for photos…

Spectroscopy

1/23/2

5/2

1/2

3/2

5/2

90 MHz7F0

5D0

119 MHz

194 MHz

260 MHz

Relative transition strengths

Branching ratio measurements:

etc…

Our choice of wavelengths

0 1 2 3 4 50

0.5

1

1.5

2

Time (s)

Tra

nsm

issi

on (

au)

with combwithout comb

Two-level AFC echo

-4 -2 0 2 40

0.2

0.4

0.6

0.8

Readout frequency (MHz)

Abs

orpt

ion

(au)

Comb preparedon the 3/2-3/2

transition

AFC-echo2% Efficiency

… has a limited lifetime

1 2 3 4 5

0

0.1

0.2

0.3

Storage time (s)

Tra

nsm

isio

n au

= 140 kHz

Rabi frequency measurements

Rabi frequency measurement on the 3/2-3/2 transition

Rabipulse

Rabi freq = 600-700 kHz

1 2 3 4-1

-0.5

0

0.5

Pulse evolution s

r3 p

op

ula

tion

inve

rsio

n

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

AFC with spin wave storage in Eu:YSO

0 5 10 15

5

10

15

x 10-3

Time (s)

Tra

nsm

isio

n au

14% of the pulse area of the two level echo recovered

… inhomogeneous spin lifetime

8 10 12 14 16

0

0.02

0.04

0.06Inhomogeneous spin width: 36 kHz

Storage time (s)

Tra

nsm

isio

n au

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:Y2SiO5 at 36 kHz

Outlook: complete AFC storage in Eu:Y2SiO5 at single photon level

Nd experimentsImam Usmani (PhD)Christoph Clausen (PhD)Félix Bussières (post-doc)

Eu experimentsBjörn Lauritzen (post-doc)Nuala Timoney (post-doc)

Mikael Afzelius, Hugues de RiedmattenNicolas Sangouard, Nicolas Gisin

Thank you!