Linear-optical four-dimensional Bell state measurement with the two-photon interference
Zhi Zeng · Journal of the Optical Society of America B · 2025
We theoretically investigate the distinguishability of a set of mutually orthogonal four-dimensional Bell states of photon system in path degree of freedom using only linear optics, resorting to the two-photon interference. With quantum interference effect, we find that the 16 four-dimensional Bell states can be classified into seven groups, which can support the transmission of log 2 7=2.81bits classical information with just sending one photon in the quantum superdense coding protocol. When an auxiliary two-dimensional polarization entanglement is introduced, the 16 four-dimensional Bell states then can be classified into 12 groups, which can promote the channel capacity to log 2 12=3.58bits with encoding one photon. Moreover, both of these two approaches can be easily realized with the current technology. Our results are significant for photonic superdense coding and can be useful for other quantum information technologies involved in linear-optical high-dimensional Bell state measurement.