Entangled photons generated by nonlinear optical interaction can be used to
study the very fundamental issues in quantum mechanics such as nonlocality etc..
And entangled photons also play the key role in quantum computation and quantum
communications. Therefore the new generation nonlinear optical material must
greatly affect the development of quantum optics. As a type of newly developed
nonlinear optical material, the optical superlattice has attracted great
interest of researchers in quantum optics. It has been 20 years since our
research group began the research on the optical superlattice. We can fabricate
kinds of optical superlattice with unique optical properties which ensures
colorful phase-matching conditions and abundant nonlinear optical coupling
processes. All these advantages in nonlinear optics can be taken in the quantum
optics. In recent several years, we began to study the nonclassical optical
properties in this material including the entangled photons, continuous variable
entanglement and so on. The main research area concludes the following issues. |
Background:
The nonlinearity
can be modulated both longitudinally and transversely in optical superlattice.
It is equivalent that a nonlinear grating is written into the nonlinear crystal.
The will definitely reforms the mode function of entangled photons. According to
this basic principle, our research mainly focus on how to control and transform
the entangled properties by the ferroelectric domain engineering technique, how
to develop the new high-dimension entangled state and how these new state will
be applied in quantum computation and quantum communication. In addition, we
also theoretically studied the three-photon and multi-photon state generated
from the optical superlattice including multi-photon interference, multi-photon
lithography and multi-photon imaging.
Results:
We successfully controlled the entangled
photon’s wave front by domain engineering technique and nonlinear
Huygens-Fresnel principle. By a
multi-channel periodically poled lithium tantalate, a high-dimensional entangled
state was generated. The structure information of this superlattice was
successfully transferred to the spatial properties of the entangled photons. A
so-called subwavelength interference effect was experimentally verified. The
results offer a new way to generate the entangled photons and can be applied in
the quantum information. In the following figure, (a) is the coincidence
counting rate when only one single photon detector scans, (b) is the coincidence
counting rate when two detectors scan in-step and (c) is the diffraction pattern
when the pump laser incident on the mask template of the multi-channel
structure. The inset is the micrograph of the multi-channel periodically poled
lithium tantalate.
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Background:
The phase-matching is very flexible inside the optical
superlattice and this can be used to generate the continuous variable
entanglement with a unique color, two different colors and even multiple colors.
The multi-component continuous variables entanglement can be used for new type
of quantum dense coding and quantum communication.
Results 1:
We theoretically studied the three-mode continuous
variable entanglement which was generated from a quasi-periodic optical
superlattice. This multi-component continuous variables entanglement actually
contains 3 primary colors of the red, green and blue. This must have new
applications in quantum communication. The left part in the following figure
displays the structure of this sample and the right part is the RGB light
generated from this sample.
Reference:Y.
B. Yu, Z. D. Xie, X. Q. Yu, H. X. Li, P. Xu, H. M. Yao, and S. N. Zhu, Phys Rev.
A 74, 042332 (2006).
Results 2:
We theoretically studied the multi-pair continuous variables
entanglement generated through the enhanced Raman process inside the optical
superlattice. A frequency-comb continuous variable entanglement with tunable
frequency interval was successfully generated. This can be used to develop a
quantum WDM. The following is the quantum correlation between the stokes and
anti-stokes Raman fields of the same order. The inset is the hexagonally pole
lithium tantalate which generated the multi-order Raman scattering spectrum.
Reference:Y.
B. Yu, S. N. Zhu, X. Q. Yu, P. Xu, J. F. Wang, Z. D. Xie, and H. Y. Leng, Phys.
Rev. A 77, 032317 (2008)
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