Quantum entanglement is a phenomenon where pairs of photons become interconnected so that any change in the state of one photon instantaneously affects the other, regardless of the distance between them. Albert Einstein famously referred to this as “spooky action at a distance.”
Today, entanglement plays a crucial role in the creation of qubits, the fundamental unit of quantum information.
Traditionally, producing pairs of entangled photons required large crystals. However, researchers at Columbia Engineering have developed a more efficient method using smaller devices and less energy.
This advancement is a significant step in the field of nonlinear optics, which involves manipulating light properties for applications such as lasers, telecommunications, and laboratory equipment.
Professor P. James Schuck of Columbia Engineering believes that this breakthrough bridges the gap between large-scale and small-scale quantum optics, paving the way for highly efficient on-chip devices like tunable microscopic photon-pair generators.
The newly developed device is incredibly thin at only 3.4 micrometers, making it suitable for integration onto a silicon chip. This innovation promises to enhance the energy efficiency and technical sophistication of quantum devices.
Researchers utilized thin molybdenum disulfide crystals to create the device, stacking six of these crystals with each layer rotated by 180 degrees. As light passes through this stack, quasi-phase-matching alters the light properties, resulting in the generation of paired photons.
This groundbreaking method marks the first time quasi-phase-matching has been applied to van der Waals materials for generating photon pairs at wavelengths beneficial for telecommunications. The new approach boasts higher efficiency and lower error rates compared to previous techniques.
Professor P. James Schuck envisions that van der Waals materials will play a pivotal role in next-generation quantum technologies, impacting fields like satellite communication and quantum communication in mobile phones.
Built on previous work
Schuck and his team built upon their previous research to enhance the new device. In 2022, they demonstrated the suitability of materials like molybdenum disulfide for nonlinear optics, although performance was limited due to light wave interference in the material.
To address this issue, they employed periodic poling to improve phase matching. By alternating the direction of slabs in the stack, they achieved better control over the light, enabling efficient photon pair generation on a miniature scale.
Schuck explained, “Once we realized the potential of this material, we knew that periodic poling could efficiently generate photon pairs.”
Journal Reference:
- Chiara Trovatello, Carino Ferrante, Birui Yang, Josip Bajo, Benjamin Braun et al. Quasi-phase-matched up- and down-conversion in periodically poled layered semiconductors. Nat. Photon, 2025 DOI: 10.1038/s41566-024-01602-z
