Quantum mechanics offers the possibility of unconditionally secure communication between multiple remote parties. Security proofs for such protocols typically rely on bounding the capacity of the quantum channel in use. In a similar manner, Cramér-Rao bounds in quantum metrology place limits on how much information can be extracted from a given quantum state about some unknown parameters of interest. In this work we establish a connection between these two areas. We first demonstrate a three-party sensing protocol, where the attainable precision is dependent on how many parties work together. This protocol is then mapped to a secure access protocol, where only by working together can the parties gain access to some high security asset. Finally, we map the same task to a communication protocol where we demonstrate that a higher mutual information can be achieved when the parties work collaboratively compared to any party working in isolation.

量子力学提供了多个远程方之间无条件安全通信的可能性。此类协议的安全证明通常依赖于限制所使用的量子通道的容量。以类似的方式，量子计量学中的克拉梅尔-饶界限限制了从给定量子态中可以提取有关某些未知感兴趣参数的信息量。在这项工作中，我们在这两个领域之间建立了联系。我们首先演示一个三方传感协议，其中可达到的精度取决于有多少方一起工作。然后，该协议被映射到安全访问协议，只有通过共同努力，各方才能访问某些高安全性资产。最后，我们将相同的任务映射到通信协议，在该协议中我们证明，与任何一方单独工作相比，当各方协作工作时可以实现更高的互信息。