Researchers have developed a new method to generate valuable pairs of photons that can interact over any distance, which could greatly impact computing, telecommunications, and sensing technologies in the future.
For more than 100 years, scientists have been studying the strange behaviors of photons, electrons, and other subatomic particles on a microscopic scale. Engineers have been working to utilize these intriguing interactions to create new technologies for several decades.
One intriguing effect, known as quantum entanglement, happens when two photons become linked such that the state of one photon instantly reflects the state of the other, regardless of the distance separating them.
Nearly 80 years ago, Albert Einstein referred to this effect as “spooky action at a distance.” Nowadays, quantum entanglement is a crucial area of research globally, especially as it relates to the key component of quantum information known as qubits.
At present, the most efficient way to produce photon pairs involves sending light through a visible crystal. A study released today in Nature Photonics by a team led by Columbia Engineering researchers reveals an innovative method for generating these photon pairs that improves performance using a significantly smaller device while consuming less energy. P. James Schuck, an associate professor of mechanical engineering at Columbia Engineering, was instrumental in leading this research effort.
This innovation represents a significant leap in nonlinear optics, a discipline focused on modifying the properties of light for applications such as lasers, telecommunications, and scientific instruments.
“This study exemplifies the long-sought ambition of bridging macroscopic and microscopic nonlinear and quantum optics,” says Schuck, co-director of Columbia’s Master’s program in Quantum Science and Technology. “It establishes the foundation for scalable, highly efficient devices that can be integrated on-chip, like adjustable microscopic generators for entangled photon pairs.”
How it works
The newly developed device, which measures just 3.4 micrometers in thickness, indicates a future where key parts of various quantum systems could be integrated into a silicon chip, leading to improved energy conservation and enhanced capabilities of quantum devices.
The researchers built the device using thin layers of a van der Waals semiconductor called molybdenum disulfide. They stacked six layers of these crystals, rotating each layer 180 degrees relative to the layers above and below it. As light travels through this arrangement, a technique called quasi-phase-matching alters the light’s properties, enabling the generation of paired photons.
This study is the first instance of using quasi-phase-matching in any van der Waals material to produce photon pairs at wavelengths suitable for telecommunications. This method is significantly more efficient than earlier approaches and is far less prone to errors.
“We believe that this discovery will place van der Waals materials at the forefront of future nonlinear and quantum photonic technologies, positioning them as prime candidates for all future on-chip technologies and potentially replacing existing bulk and periodically poled crystals,” Schuck states.
“These innovations will promptly influence various areas, including satellite-based distribution and mobile quantum communication.”
How it happened
Schuck and his team built upon previous studies to create the new device. In 2022, they showed that materials such as molybdenum disulfidehave helpful properties for nonlinear optics, although their performance was limited due to interference from light waves within the material.
To overcome this issue known as phase matching, the team adopted a technique called periodic poling. By alternating the orientation of the layers in the stack, the device alters light behavior, enabling photon pair generation at a remarkably small scale.
“Once we discovered the remarkable abilities of this material, we felt inclined to use periodic poling as it would allow the efficient creation of photon pairs,” mentions Schuck.
This research was conducted under the Programmable Quantum Materials initiative, an energy frontier research center (EFRC) supported by the Department of Energy at Columbia. It received contributions from the Baso, Delor, and Dean laboratories, with postdoctoral researcher Chiara Trovatello leading the project.
