Columbia Engineering researchers have taken another step toward shrinking quantum hardware.<\/p>\n
The team has created an ultrathin metasurface device that boosts nonlinear optical effects at the nanoscale.<\/p>\n
The advance builds on work published earlier this year, when the group showed that a crystalline device just 3.4 micrometers thick could generate entangled photon pairs.<\/p>\n
The new study shows how the team cut that scale down to only 160 nanometers.<\/p>\n
They achieved this by introducing metasurfaces. These structures rely on artificial patterns etched into ultrathin crystals to unlock optical behaviors not found in nature.<\/p>\n
Corresponding author Chiara Trovatello said the group found a reliable approach to engineer these materials.<\/p>\n
\u201cWe\u2019ve established a successful recipe to pattern ultrathin crystals at the nanoscale to enhance nonlinearity while maintaining their sub-wavelength-thickness,\u201d she said. Trovatello is now an assistant professor at Politecnico di Milano.<\/p>\n
The Schuck lab works with transition metal dichalcogenides. These crystals can be peeled into layers only atoms thick.<\/p>\n
Researchers stack them to create optical properties suited for quantum systems. But the layers remained too thin to generate photons efficiently. That limited the material\u2019s usefulness.<\/p>\n
Trovatello said quantum hardware demands compact components. She noted that current qubit sources occupy several centimeters and require large equipment rooms.<\/p>\n
\u201cTo make quantum technologies scalable, we need to shrink the size of our qubit sources,\u201d she said.<\/p>\n
Earlier this year, the group used periodic poling to generate photons<\/a> by arranging layers of molybdenum disulfide in alternating directions. That alignment ensured proper phase matching.<\/p>\n The new work takes a different route. PhD student Zhi Hao Peng etched repeating nanoscale lines into a molybdenum disulfide flake. The pattern created strong nonlinear effects beyond what traditional tuning could achieve.<\/p>\n \u201cOur design enhances the nonlinear effects much more than traditional linear optical optimization techniques, and therefore achieves strong enhancement not previously possible,\u201d Peng said.<\/p>\n The metasurface increased second harmonic generation by nearly 150 times relative to unpatterned samples. In that process, two photons merge into one with double the frequency.<\/p>\n The team now aims to reverse the conversion and split one photon into two entangled photons.<\/p>\n Peng\u2019s method also reduces fabrication complexity. Jim Schuck, the senior investigator, highlighted that benefit.<\/p>\n \u201cNonlinear crystals have been key to a lot of photonic technologies, but these materials can be brittle and have been notoriously difficult to shape and fabricate,\u201d he said.<\/p>\n He added that Peng created a simple approach that works with standard cleanroom tools.<\/p>\n Toward on-chip quantum systems<\/p>\n Theoretical collaborators helped identify the best pattern for large nonlinear responses. Michele Cortufo said the structure relied on alternating line widths to achieve \u201cnontrivial behavior\u201d in flakes this thin.<\/p>\n Andrea Alu noted that the work shows how engineered nonlocalities in metasurfaces can enable \u201ccompact, integrable platforms\u201d for nonlinear optics.<\/p>\n The device operates at telecom wavelengths, which makes future integration easier. Schuck said the footprint points toward fully on-chip quantum<\/a> photonics.<\/p>\n