Direct counterfactual quantum-communication protocol beyond a single-photon source
Zheng-Hong Li, Shang-Yue Feng, M. Al-Amri, M. Suhail Zubairy
Abstract
The direct counterfactual quantum-communication protocol involving double-chained Mach-Zehnder interferometers requires a single-photon input. Here, we show that even with multiphoton light sources, including a strong coherent light source as input, the counterfactual communication can be achieved with success probability approaching unity in the ideal asymptotic limit. The path evolution of multiple photons is nonlocally controlled. Thus, information is transmitted without any photons, or any other auxiliary information carriers, appearing in the public transmission channel. The effect is quantum since quantum measurements are an essential requirement for this protocol. Furthermore, a modified scheme is proposed in which the number of interferometers is reduced.