Quantum entanglement is an important resource for quantum information. Polarization entangled Bell states are the most widely used entangled biphoton states in quantum optics experiments. Simple and reliable quantum light sources for polarization entangled Bell state generation are desired, especially at telecom-band for quantum communications over optical fibers.

In this work, frequency-degenerate biphoton states were generated in four silicon waveguides by spontaneous four-wave mixing. They were transformed to polarization entangled Bell states through on-chip quantum interference and quantum superposition, and then coupled to optical fibers. The chip can output two Bell states, which were demonstrated by the experiments of simplified Bell state measurement. It is shown that the chip supported a quantum state modulation rate of several tens of kHz. This function could be used as quantum information encoding based on the Bell states, which has important applications in quantum communications and quantum information processing.

This work has been accepted by the first issue of Chip (Volume 1, Issue 1, 100001; https://www.sciencedirect.com/science/article/pii/S2709472321000010; 

DOI: 10.1016/j.chip.2021.100001) and online published on 16th Feb. 2022. The co-first author of this paper are Dr. Lingjie yu, Ph.D. candidate Dongning Liu and Jingyuan Zheng. The corresponding author of this paper is Prof. Wei Zhang.