  The transmission of strong laser light in nonlinear optical materials can
generate output photons sources that carry quantum entanglement in multiple
degrees of freedom, making this process a fundamentally important tool in
optical quantum technology. However, the availability of efficient optical
crystals for entangled light generation is severely limited in terms of
diversity, thus reducing the prospects for the implementation of
next-generation protocols in quantum sensing, communication and computing. To
overcome this, we developed and implemented a multi-scale first-principles
modeling technique for the computational discovery of novel nonlinear optical
devices based on metal-organic framework (MOF) materials that can efficiently
generate entangled light via spontaneous parametric down-conversion(SPDC).
Using collinear degenerate type-I SPDC as a case study, we computationally
screen a database of 114,373 synthesized MOF materials to establish
correlations between the structure and chemical composition of MOFs with the
brightness and coherence properties of entangled photon pairs. We identify a
subset of 49 non-centrosymmetric mono-ligand MOF crystals with high chemical
and optical stability that produce entangled photon pairs with intrinsic
$G^{(2)}$ correlation times $\tau_c\sim 10-30$ fs and pair generation rates in
the range $10^4-10^{8}$ s$^{-1}$mW$^{-1}$mm$^{-1}$ at 1064 nm. Conditions for
optimal type-I phase matching are given for each MOF and relationships between
pair brightness, crystal band gap and optical birefringence are discussed.
Correlations between the optical properties of crystals and their constituent
molecular ligands are also given. Our work paves the way for the computational
design of MOF-based devices for optical quantum technology.
