Timur Sh. Iskhakov, Ivan N. Agafonov, Maria V. Chekhova, Gerd Leuchs
Entanglement is the signature of the quantum world. One part of an entangled
system has its properties fully undefined yet fully correlated with the
properties of its counterpart [1]. Can this behavior be observed for large
objects? Recently, entanglement was discovered for macroscopic material systems
[2, 3]. It is very tempting to observe it for bright photonic states [4, 5]
because light interacts the more efficiently the more photons it contains. For
bright squeezed vacuum, very different from usual squeezed light, entanglement
was discussed theoretically [6-10] but never tested experimentally. Coincidence
measurements could only reveal entanglement for up to 12 photons [11]. Here we
experimentally demonstrate entanglement for squeezed vacuum pulses containing
more than 10^5 photons. We also calculate their Schmidt number and measure its
operational counterpart [12]. Theoretically, our pulses are the more entangled
the brighter they are. This promises important applications in quantum
technologies, especially photonic quantum gates and quantum memories [13].
View original:
http://arxiv.org/abs/1111.2073
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