De Novo Design of a Non-Cryogenic Quantum Interface: Tuning Erbium Emission to the Telecom C-Band within a Synthetic Protein Scaffold

The development of scalable quantum networks is fundamentally limited by the cryogenic infrastructure required by current solid-state quantum emitters, restricting deployment beyond laboratory settings. Here, we present a computational demonstration of non-cryogenic (277 K) quantum-compatible emission at telecommunication wavelengths from erbium(III) ions embedded in a de novo designed protein scaffold. Building upon our previously proposed "Biological Anchor" architecture for hybrid bio-quantum communication systems ³ ¹, we designed and computationally characterized a chimeric protein, which we term Teledrybin, featuring a modified EF-hand motif optimized for asymmetric 9-coordinate Er³⁺ binding. Using complete active space self-consistent field (CASSCF) calculations with N-electron valence state perturbation theory (NEVPT2) and spin-orbit coupling (SOC), we predict optical transitions at 1554 nm, precisely within the telecommunications C-band (1530–1565 nm). Molecular dynamics simulations at 277 K in H₂O (to be replaced by D₂O on field) demonstrate structural stability over 140 ns, with the Er³⁺ coordination geometry converging to average Er–O distances of 2.34–2.36 Å and angular deviations below 2° across independent AlphaFold3 models. The low-symmetry (C₁) coordination environment enables the otherwise Laporte-forbidden 4f-4f transitions, while the engineered hydrophobic barrier suppresses vibrational quenching by excluding bulk solvent from the binding site—only a single structural D₂O molecule remains coordinated. These results validate the feasibility of protein-based quantum emitters operating under non-cryogenic conditions in the telecom band, offering a biologically-producible, scalable alternative to solid-state quantum light sources for edge-node applications in quantum networks.