Silicon carbide chip generates fast, high-quality entangled photon pairs

Cavity-enhanced photon-pair sources typically face a hard trade-off: higher quality factors boost generation efficiency but narrow the photon bandwidth, throttling data rates in quantum networks. By carefully engineering both the nonlinear properties of 4H-SiC and the microring geometry, this chip achieves a 1 GHz spectral bandwidth alongside a pair-generation rate of 1.35 × 10⁷ s⁻¹ mW⁻², with raw entanglement visibility of 95.6% and a Bell inequality violation exceeding 138 standard deviations. The result demonstrates that material and geometry co-optimization can break the efficiency–bandwidth constraint without sacrificing entanglement quality, pointing toward scalable, chip-integrated sources for high-speed quantum communication.