Experimental Observation of Simultaneous Wave and Particle Behaviors in   a Narrowband Single Photon's Wave Packe
  Light's wave-particle duality is at the heart of quantum mechanics and can be well illustrated by Wheeler's delayed-choice experiment. The choice of inserting or removing the second classical (quantum) beam splitter in a Mach-Zehnder interferometer determines the classical (quantum) wave-particle behaviors of a photon. In this paper, we report our experiment using the classical beam splitter to observe the simultaneous wave-particle behaviors in the wave-packet of a narrowband single photon. This observation suggests that it is necessary to generalize the current quantum wave-particle duality theory. Our experiment demonstrates that the produced wave-particle state can be considered an additional degree of freedom and can be utilized in encoding quantum information. 
H. Yan, K. Liao, Z. Deng, J. He, Z. Y. Xue, Z. M. Zhang, and S. L. Zhu
quant-ph