npj Quantum Information (Mar 2025)

Realizing ultrahigh capacity quantum superdense coding on quantum photonic chip

  • Yuan Li,
  • Huihui Zhu,
  • Wei Luo,
  • Hong Cai,
  • Muhammad Faeyz Karim,
  • Xianshu Luo,
  • Feng Gao,
  • Xiang Wu,
  • Xiaoqi Zhou,
  • Qinghua Song,
  • Leong Chuan Kwek,
  • Ai Qun Liu

DOI
https://doi.org/10.1038/s41534-025-01007-y
Journal volume & issue
Vol. 11, no. 1
pp. 1 – 6

Abstract

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Abstract 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 $${{0.973}}\pm {{0.002}}$$ 0.973 ± 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 $${{3.021}}\pm {{0.003}}$$ 3.021 ± 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.