Realizing ultrahigh capacity quantum superdense coding on quantum photonic chip
Yuan Li, Huihui Zhu, Wei Luo, Hong Nian Cai, Muhammad Faeyz Karim, Xianshu Luo, Feng Gao, Xiang Xia Wu, Xiaoqi Zhou, Qinghua Song, L. C. Kwek, A. Q. Liu · npj Quantum Information · 2025
Quantum superdense coding provides a compelling solution to enhance the channel capacity compared with classical coding, which plays a vital role in quantum networks. However, the realization of a degenerate high-dimensional entangled state with high fidelity has remained an elusive challenge, limiting improvement in channel capacity. Here, we have demonstrated a 16-mode quantum process photonic chip and experimentally validated a degenerate eight-dimensional quDit entangled state with a fidelity of $${{0.973}}\pm {{0.002}}$$ . Moreover, we propose an efficient Bell state measurement method to distinguish eleven orthogonal Bell states in eight-dimensional quantum superdense coding. Leveraging the high-quality features of our quantum photonic chip, we have achieved an unprecedented channel capacity of $${{3.021}}\pm {{0.003}}$$ bits, highlighting the largest channel capacity to date. Furthermore, our method presents a remarkable quantum advantage over classical schemes, the latter of which can only transmit a maximum of 3 bits in the environment without any noise. Our findings not only open up a new avenue for integrated quantum information processing, but also contribute significantly to the advancement of multidimensional technologies, facilitating the establishment of practical, high-capacity quantum networks.