This research presents a breakthrough in quantum communication through the implementation of high-dimensional quantum superdense coding on an integrated photonic chip. The work addresses a fundamental challenge in quantum networks: increasing channel capacity beyond classical limitations.
The researchers have successfully demonstrated an eight-dimensional quantum superdense coding protocol using a 16-mode quantum photonic chip. At its core, the achievement rests on generating a degenerate eight-dimensional quDit entangled state with high fidelity—a crucial requirement that had previously proven difficult to achieve. This high-quality entangled state serves as the foundation for the protocol’s enhanced capacity.
A key innovation is the development of an efficient Bell state measurement technique capable of distinguishing eleven orthogonal Bell states in the eight-dimensional space. This measurement capability is essential for decoding the quantum information transmitted through the protocol.
The experimental results are impressive, achieving an unprecedented channel capacity of over 3 bits—the highest reported to date. This represents a significant quantum advantage over classical communication schemes, which are fundamentally limited to 3 bits in an eight-dimensional space under ideal, noise-free conditions.
The silicon-based photonic chip implementation offers several advantages over traditional optical setups, including improved stability, compatibility, and programmability. The chip’s precise thermal control enables accurate high-fidelity qubit operations, making complex quantum protocols feasible in a compact form factor.
The work demonstrates how increasing the dimensionality of quantum states provides an effective pathway to enhance channel capacity in quantum communication. By utilizing photons—which are particularly well-suited for communication due to their high transmission speed and low loss in optical fibers—the research addresses practical concerns for long-distance quantum networks.
This proof-of-principle demonstration opens new avenues for integrated quantum information processing and contributes significantly to the advancement of high-dimensional quantum technologies. The research has important implications for the development of practical, high-capacity quantum networks and communications systems that can surpass classical limits.
Reference: Li, Y., Zhu, H., Luo, W. et al. Realizing ultrahigh capacity quantum superdense coding on quantum photonic chip. npj Quantum Inf 11, 49 (2025). doi:10.1038/s41534-025-01007-y
