A novel \(2\) \& \(3\) player scheme for Quantum Direct Communication

This paper introduces two information-theoretically secure protocols that achieve quantum secure direct communication between Alice and Bob in the first case, and among Alice, Bod and Charlie in the second case. Both protocols use the same novel method to embed the secret information in the entangled compound system. The way of encoding the information is the main novelty of this paper and the distinguishing feature compared to previous works in this field. The most critical advantage of this method is that it is easily scalable and extensible because it can be seamlessly generalized to a setting involving three, or even more, players, as demonstrated with the second protocol. This trait can be extremely beneficial when many spatially separated players posses only part the secret information that must be combined and transmitted to Alice, so that she can obtain the complete secret. Using the three player protocol, this task can be achieved in one go, without the need to apply a typical QSDC protocol twice, where Alice first receives Bob's information and afterwards Charlie's information. The proposed protocol doesn't require pre-shared keys or quantum signatures, making it less complicated and more straightforward. Finally, by employing only standard CNOT and Hadamard gates, it offers the important practical advantage of being implementable on contemporary quantum computers, especially in view of the coming era of quantum distributed computing.