Department of Computing and Mathematical Sciences, California Institute of Technology, 1200 E California Boulevard, Pasadena, California 91125, USA.
Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543, Singapore.
Nat Commun. 2017 May 26;8:15485. doi: 10.1038/ncomms15485.
Quantum technologies promise advantages over their classical counterparts in the fields of computation, security and sensing. It is thus desirable that classical users are able to obtain guarantees on quantum devices, even without any knowledge of their inner workings. That such classical certification is possible at all is remarkable: it is a consequence of the violation of Bell inequalities by entangled quantum systems. Device-independent self-testing refers to the most complete such certification: it enables a classical user to uniquely identify the quantum state shared by uncharacterized devices by simply inspecting the correlations of measurement outcomes. Self-testing was first demonstrated for the singlet state and a few other examples of self-testable states were reported in recent years. Here, we address the long-standing open question of whether every pure bipartite entangled state is self-testable. We answer it affirmatively by providing explicit self-testing correlations for all such states.
量子技术在计算、安全和传感等领域有望超越经典技术。因此，理想情况下，即使没有量子设备的内部工作原理的任何知识，经典用户也能够获得量子设备的保证。经典认证成为可能是非常显著的：这是由纠缠量子系统违反贝尔不等式的结果。设备无关的自我测试是指最完整的这种认证：它使经典用户通过简单地检查测量结果的相关性，就能够唯一地识别由未特征化的设备共享的量子态。自我测试首先在单重态中得到了证明，近年来还报道了一些其他自测试态的例子。在这里，我们解决了长期存在的一个开放性问题，即是否每个纯双粒子纠缠态都是可自我测试的。我们通过为所有此类状态提供明确的自我测试相关性，给出了肯定的回答。
