Quantum Counterfactual Communication is the recently-proposed idea of using quantum physics to send messages between two parties, without any matter/energy transfer associated with the bits sent. While this has excited massive interest, both for potential ‘unhackable’ communication, and insight into the foundations of quantum mechanics, it has been asked whether this process is essentially quantum, or could be performed classically. We examine counterfactual communication, both classical and quantum, and show that the protocols proposed so far for sending signals that don’t involve matter/energy transfer associated with the bits sent must be quantum, insofar as they require wave-particle duality.

量子反事实通信是最近提出的想法，即使用量子物理学在两方之间发送消息，而无需与所发送的位相关联的任何物质/能量传输。尽管这引起了巨大的兴趣，包括对潜在的“无法破解的”通信以及对量子力学基础的洞察力，但有人问这个过程本质上是量子的，还是可以经典地进行的。我们研究了反事实通信，包括经典通信和量子通信，并表明，到目前为止，所提出的用于发送不涉及与所发送比特相关的物质/能量转移的信号的协议必须是量子的，因为它们需要波粒对偶。