Free-space optical communication based on photonic orbital angular momentum (OAM), including OAM multiplexing and OAM modulation schemes, has the potential to greatly increase information transfer capacity. However, the presence of atmospheric turbulence can severely distort the spatial modes of OAM beams, resulting in modal scattering and distortions. In this study, we theoretically develop a method to control the total OAM of a superimposed OAM beam (total OAM in a superposition state but not the OAM eigenstate in general)—coherent superposition of $N$ OAM eigenstates—propagating through the time-varying atmospheric turbulence by dynamically modulating the complex coefficient of each OAM eigenstate and experimentally demonstrate the total OAM control strategy. Our experimental results show that the control error of total average OAM per photon is around $0.1\hslash$ in a turbulent channel with a scintillation index of 1.03, and the control strategy is effective even in nonunitary turbulent systems. Furthermore, we successfully receive a data packet using two-OAM-eigenstate-superposition beams for two bits per pulse in unitary and nonunitary turbulent channels. Our study offers an effective way to control the OAM of light beams propagating in turbulent media, which will find potential applications in free-space optical communication and remote sensing.

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• Optical quantum information processing
• Optical vortices
• Quantum communication
• Spatial profiles of optical beams
• Turbulence
• Earth's atmosphere
• Quantum networks
• Wireless communication networks