Researchers at Heilongjiang University have created a quantum gate using a single-layer gradient metasurface, a development published in Quantum Science and Technology on September 7, 2026. The team achieved a high-fidelity optical controlled-Y (CY) gate, an essential component for universal quantum computation, with their design. This metasurface, composed of 26 amorphous-silicon pillars, performs parallel beam splitting, diffraction routing, and two-photon interference to realize both controlled bit-flips and precise phase factors.
After fixed local polarization encoding/analysis transformations and coincidence post-selection, the reconstructed two-photon gate matrix matches the ideal CY unitary with a matrix fidelity of 0.9885. The results establish a compact platform for phase-sensitive controlled quantum logic and entangled-state manipulation.
Pancharatnam-Berry Metasurface Enables Optical Controlled-Y Gate
A single-layer metasurface achieved a matrix fidelity of 0.9885. This performance is notable because the CY gate is a fundamental component required for universal quantum computation, demanding both controlled bit-flips and precise phase manipulation. Researchers from Heilongjiang University detail how polarization-encoded photons interact with the metasurface to create the necessary quantum effects. Computational tests of the gate’s performance reveal high fidelity across multiple measurement bases; ZZ- and XY-basis truth tables yielded fidelities of 0.9902 and 0.9924, respectively.
Further analysis demonstrated an average fidelity of 0.9902 for the four phase-type Bell states generated by the gate, indicating a strong capacity for entangled-state manipulation. The design operates at a wavelength of 1550 nm, a standard in optical communications, and simulations suggest a bandwidth of approximately 26.5 nm, indicating potential for integration with existing photonic infrastructure.
The work establishes a monolithic platform for phase-sensitive controlled quantum logic, with an average post-selection success probability of 0.0976 extracted from full-wave simulations. Dongyan Li, Weihao Zhang, Yaru Li, and Guoqiang Lan of the School of Electronic Engineering, Heilongjiang University, conducted the research and are also affiliated with the Heilongjiang Provincial Key Laboratory of Micro-nano Sensitive Devices and Systems.
See today’s quantum computing news on Quantum Zeitgeist for the latest breakthroughs in qubits, hardware, algorithms, and industry deals.
