atoms

Quadripartite entanglement
• 4 atomic ensembles sharing 1 quantum of spin excitation
K. Choi, A. Goban, S. Papp, S. J. van Enk & H. J. Kimble, Nature 468, 412 (2010)
W ideal
= 1 2
⎡( 1000 + e iφ 1
0100 ) + e iφ 0010 + e iφ 2
⎣
0001
( )
⎤
⎦
exp
⇔ ˆρ atoms
exp
Inferred fidelity F atoms
exp
F atoms
for atomic W state at memory time τ 0
= 0.2µs:
exp
= W ideal
ˆρ atoms
W ideal
= 0.9 ± 0.1
Fluorescent image
from 4 ensembles