Efficient quantum state tomography
Efficient quantum state tomography
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DOI：
10.1038/ncomms1147
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发表时间：
2010-12-01
影响因子：
16.6
通讯作者：
Liu, Yi-Kai
中科院分区：
文献类型：
--
作者：
Cramer, Marcus;Plenio, Martin B.;Liu, Yi-Kai
量子态层析——从测量数据中推断量子态——是量子器件验证和基准测试的黄金标准。它已经在组件较少的系统中实现，但对于较大的系统，它变得不可行，因为测量的数量和处理它们所需的计算量随着系统规模呈指数级增长。在这里，我们提出了两种断层扫描方案，它们比系统大小的直接断层扫描更有利。其中一种方法需要对恒定数量的子系统进行统一操作，而另一种方法只需要局部测量和更精细的后处理。两者都只依赖于线性数量的实验操作和系统大小的多项式的后处理。这些方案可以应用于广泛的量子态，特别是那些很好地近似矩阵积态。重构状态的准确性可以在没有任何先验假设的情况下得到严格证明。
Quantum state tomography-deducing quantum states from measured data-is the gold standard for verification and benchmarking of quantum devices. It has been realized in systems with few components, but for larger systems it becomes unfeasible because the number of measurements and the amount of computation required to process them grows exponentially in the system size. Here, we present two tomography schemes that scale much more favourably than direct tomography with system size. One of them requires unitary operations on a constant number of subsystems, whereas the other requires only local measurements together with more elaborate post-processing. Both rely only on a linear number of experimental operations and post-processing that is polynomial in the system size. These schemes can be applied to a wide range of quantum states, in particular those that are well approximated by matrix product states. The accuracy of the reconstructed states can be rigorously certified without any a priori assumptions.