Direct generation of time-energy-entangled W-triphotons in atomic vapor

Efficiently creating dependable triphotons with nonclassical correlations distributed across all three particles has long been a goal in quantum optics. Generating these triphotons directly through one-step high-order nonlinear optical process is crucial in nonlinear and quantum optics, with potential applications in quantum information science and technologies. Here, we conducted the first experiment demonstrating a new method to produce genuine time-energy-entangled W-class triphotons through spontaneous six-wave mixing. By inputting three classical continuous-wave lasers, we observed three spatially separated newborn photons with different colors. These triphotons exhibit strong spectral quantum correlations and can be manipulated to achieve versatile multi-frequency entangled states. Reliable triphoton sources are essential for various quantum information processing applications, providing a quantum advantage.