Physikalisches Institut and Research Center SCOPE, University of Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany.
Phys Rev Lett. 2012 Nov 2;109(18):180501. doi: 10.1103/PhysRevLett.109.180501.
An important task for quantum-information processing is optimal discrimination between two nonorthogonal quantum states, which until now has been realized only optically. Here, we present and compare experimental realizations of optimal quantum measurements for distinguishing between two nonorthogonal quantum states encoded in a single (14)N nuclear spin at a nitrogen-vacancy defect in diamond. Implemented measurement schemes are the minimum-error measurement (known as Helstrom measurement), unambiguous state discrimination using a standard projective measurement, and optimal unambiguous state discrimination [known as Ivanovic-Dieks-Peres (IDP) measurement], which utilizes a three-dimensional Hilbert space. This allows us to benchmark the IDP measurement against the standard projective measurements. Measurement efficiencies are found to be above 80% for all schemes and reach a value of 90% for the IDP measurement.
量子信息处理的一个重要任务是对两个非正交量子态进行最佳区分，到目前为止，这仅在光学上实现。在这里，我们展示并比较了在钻石中氮空位缺陷处单个 (14)N 核自旋中编码的两个非正交量子态的最佳量子测量的实验实现。所实现的测量方案是最小误差测量（称为赫尔斯特姆测量）、使用标准投影测量进行的明确状态区分，以及最佳明确状态区分[称为伊万诺维奇-迪克-佩雷斯（IDP）测量]，它利用了一个三维希尔伯特空间。这使我们能够将 IDP 测量与标准投影测量进行基准测试。对于所有方案，测量效率都高于 80%，对于 IDP 测量，效率达到 90%。
