This groundbreaking research presents a fully integrated CMOS-fabricated silicon photonic circuit that combines critical quantum photonic functions on a single chip. The device employs a bidirectionally pumped microring resonator and polarization splitter-rotators specifically designed to generate broadband polarization-entangled photons across more than 9 THz with remarkable fidelity (90-98%).
Oak Ridge National Laboratory (ORNL) scientists have successfully demonstrated this innovative chip that spans the optical C+L-band, producing over 116 frequency-bin pairs on a 38.4-GHz-spaced grid. This achievement makes the device particularly suitable for flex-grid wavelength-multiplexed entanglement distribution in multiuser quantum networks.
The research, published in Optica Quantum, represents a significant advancement in quantum information science, particularly in photonic quantum computing which uses photons to create qubits for transmitting and storing information.
What distinguishes this achievement is the integration of multiple quantum photonic capabilities on a single chip. As Joe Lukens, senior author and associate professor at Purdue University with a joint appointment at ORNL, explains, “We’re not the first to put any one of these elements on a chip, but we’re the first to put these specific capabilities on a single one.” The standardized manufacturing specifications enable mass production at scale, moving quantum technology beyond laboratory demonstrations toward practical applications in a quantum internet.
The chip design incorporates essential components including a microring resonator for generating entangled photon pairs and polarization splitter-rotators that separate input light based on polarization. This integration enables direct generation of broadband polarization entanglement. Critically, the photonic qubits are compatible with existing fiber-optic infrastructure, potentially eliminating the need for costly new installations.
With more than 116 distinct channel pairs demonstrated and high fidelity across over 100 of these channels, the team has achieved what they describe as a “record number.” The use of microring resonators could eventually enable the creation of hyperentangled qubits—entangled in multiple ways such as by both polarization and color, potentially increasing information density.
This innovation represents a crucial step toward developing a practical, scalable quantum internet that can leverage existing telecommunications infrastructure while providing the enhanced security and computational power of quantum information systems.
Reference: “CMOS photonic integrated source of broadband polarization-entangled photons” by Karthik V. Myilswamy, Hsuan-Hao Lu, Saleha Fatema, Joseph M. Lukens, Alexander Miloshevsky, Andrew M. Weiner, Lucas M. Cohen and Muneer Alshowkan, 24 August 2024, Optica Quantum. DOI: doi:10.1364/OPTICAQ.521418
