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Multipartite entanglement and Multipartite entanglement and
sudden death in Quantum Optics: sudden death in Quantum Optics:
continuous variables domaincontinuous variables domain
Part IV Part IV –– Multicolor entanglementMulticolor entanglement
Marcelo Martinelli
Entangled fields- Vacuum (P0 < Pth, maximum entanglement)- Intense beams (P0 > Pth)
Squeezed vacuum (P0 < Pth, degenerate)Twin beams (P0 > Pth)
Pump Squeezing (P0 > Pth)
Set up
Direct Production of Tripartite Entanglement in the Above-Threshold OPO A. S. Villar et al. PRL 97, 140504 (2006)
Tripartite entanglement?
Quantum Correlations between pump, signal and idler for P0 > Pth
K. N. Cassemiro et al. Opt. Lett. 32, 695 (2007)
K. N. Cassemiro et al. Opt. Exp. 15, 18326 (2007)
N. B. Grosse et al. PRL 100, 243601 (2008) (degenerate case)
Three-color quantum correlationsK. N. Cassemiro et al. Opt. Lett. 32, 695 (2007)
The quest for three-color entanglement…K. N. Cassemiro et al. Opt. Exp. 15, 18326 (2007)
Noise in the reflected pump!
An open question: What is the source of the noise in the crystal?
Noise is everywhere!
0 5 10 15 20 25 30 35 40
1.0
1.5
2.0
2.5
3.0N
oise
(nor
mal
ized
to S
QL)
Reflected Power (mW)
-8 -4 0 4 8
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
Cavity Detuning (normalized to bandwidth)
-1
0
1
Ana
lisys
Cav
ity R
efle
ctan
ce
N
oise
(nor
mal
ized
to S
QL)
0 1 2 3 4 5 6 7
1.0
1.2
1.4
1.6
1.8
Noi
se (n
orm
aliz
ed to
SQ
L)
Transmitted Power (mW)
∆2p1
∆2q1
∆2p2
∆2q2
0 5 10 15 20 250.0
0.2
0.4
0.6
0.8
Transmitted Power - mode 1 (1064 nm) 13.5mW 8.3mW
Cov
aria
nce
(SQ
L un
its)
Reflected Power - mode 0 (mW)0 1 2 3 4 5 6 7
0.0
0.2
0.4
0.6
0.8
Cor
rela
tion
(nor
mal
ized
to S
QL)
Reflected Power - mode 0 (532 nm) 62 mW 39 mW
Transmitted Power - mode 1 (mW)
ω0
Is the noise inside the crystal… as a random modulationof the refractive index?
X
Y
φ
|α |
ω0 ω0
Grosse et al. PRL 100 243601(2008)
GAWBS?
Or phonon scattering?
260 280 300 320 340 360 3800.0
0.2
0.4
0.6
0.8
1.0
Cou
plin
g co
effic
ient
η00
(1/W
)
Temperature (K)
Way to go
1.0 1.1 1.2 1.3 1.4 1.5 1.6
-1
0
1
2
3
4
Cov
aria
nce
(SQ
L un
its)
Pin/Pth
q0q0 q1q1 q2q2 q0q1 q1q2 q2q0
1.0 1.1 1.2 1.3 1.4 1.5 1.6
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
Cov
aria
nce
(SQ
L un
its)
Pin/Pth
p0p0 p1p1 p2p2 p0p1 p1p2 p2p0
1.0 1.1 1.2 1.3 1.4 1.5 1.6
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
Cov
aria
nce
(SQ
L)
Pin/Pth
p0p0 p1p1 p2p2 p0p1 p1p2 p2p0
1.0 1.1 1.2 1.3 1.4 1.5 1.6
-1
0
1
2
3
4
Cov
aria
nce
(SQ
L)
Pin/Pth
q0q0 q1q1 q2q2 q0q1 q1q2 q2q0
The effect of losses
The problem of decoherenceIs the main problem for an eventual quantum computer, operating over many entangled qubits.
What is the limit for this entanglement?
Interaction with the environment!
Why producing and keeping them is a hard task?
Decoherence: as if the environment where continuously measuring the system!
Famous example: Schrödinger Cat Paradox (1935).
Also an entangled state
No more “surprises”?Disentanglement for a Bipartite & Gaussian state
Scenario (1): robust entanglement
Scenario (2):disentanglement
Disentanglement for a simpler model:Attenuation on a single beam
Tighter conditions for transmission of quantum entanglement!
Duan (optimized)
More to More to followfollow: use : use thethe OPO as a OPO as a coloredcolored entanglingentangling tooltool
Felippe Barbosa Antônio Sales Jonatas César
Alencar Faria Luciano Cruz Paulo Valente
Mikael Lassen (MPI) Alessandro Villar
Katiúscia Cassemiro Kaled Dechoum A. Zelaquett Khoury
Claude Fabre (LKB) Marcelo Martinelli Paulo Nussenzveig
Raiders of the Lost Entanglement
Paulo Nussenzveig (1996)
Marcelo Martinelli (2004)
Alessandro Villar (Post-doc)
Márcio Heráclyto (Post-doc)
Antônio Sales (PhD – MSc 2008)
Felippe Barbosa (PhD – MSc 2008)
Hans Marin Torres (MSc)
Flávio Moraes (MSc)
Paula Meirelles (PhD)
Laboratório de Manipulação Coerente de Átomos e Luz
Muchas Gracias
Los invito a visitarnos!
Y quién sabe quedarse un poco por allá!
