如何隐藏秘密方向
How to hide a secret direction
摘要：
我们提出了一个在没有公共参考系的情况下使用多体量子态共享秘密空间方向的过程。该过程保证各方可以确定的方向，如果他们对状态进行联合测量，但不能这样做，如果他们限制自己的本地操作和经典通信（LOCC）。我们计算联合测量的保真度，给出LOCC所能达到的保真度的界限，并证明了它们之间存在一个非零的差距，即使在无限多个副本的限制。粒子损失下的程序的鲁棒性进行了研究。作为一个副产品，我们发现的LOCC之间的不变子空间的总角动量N/2和N/2-1在一个系统的N个基本的自旋的歧视的概率的界限。
英文摘要：
We present a procedure to share a secret spatial direction in the absence of a common reference frame using a multipartite quantum state. The procedure guarantees that the parties can determine the direction if they perform joint measurements on the state, but fail to do so if they restrict themselves to local operations and classical communication (LOCC). We calculate the fidelity for joint measurements, give bounds on the fidelity achievable by LOCC, and prove that there is a non-vanishing gap between the two of them, even in the limit of infinitely many copies. The robustness of the procedure under particle loss is also studied. As a by-product we find bounds on the probability of discriminating by LOCC between the invariant subspaces of total angular momentum N/2 and N/2-1 in a system of N elementary spins.
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