Coherent manipulation of a three-dimensional maximally entangled state

Understand

Maximally entangled photon pairs with a spatial degree of freedom is a potential way for realizing high-capacity quantum computing and communication.

• However, methods to generate such entangled states with high quality, high brightness, and good controllability are needed.
• Here, a scheme is experimentally demonstrated that generates spatially maximally entangled photon pairs with an orbital angular momentum degree of freedom via spontaneous parametric down-conversion in a nonlinear crystal.
• Compared with existing methods using post-selection, the technique can directly modulate the spatial spectrum of down-converted photon pairs by engineering the input pump beam.