Weak measurements are universal.
Weak measurements are universal.
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DOI：
10.1103/physrevlett.95.110409
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发表时间：
2005-03
影响因子：
8.6
通讯作者：
O. Oreshkov;T. Brun
中科院分区：
文献类型：
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作者：
O. Oreshkov;T. Brun
众所周知，任何投影测量都可以分解为一系列弱测量，这些弱测量只会引起状态的微小变化。然而，用于广义测量的类似构造依赖于辅助系统的使用。我们证明了任何广义测量都可以分解成一个弱测量序列而不需要使用辅助，并给出了这些弱测量的显式构造。测量过程具有沿着状态空间中的曲线沿着随机游走的结构，其中当到达端点之一时测量结束。这表明任何测量都可以由弱测量产生，因此弱测量是普适的。这可能对纠缠理论有重要的应用。
It is well known that any projective measurement can be decomposed into a sequence of weak measurements, which cause only small changes to the state. Similar constructions for generalized measurements, however, have relied on the use of an ancilla system. We show that any generalized measurement can be decomposed into a sequence of weak measurements without the use of an ancilla, and give an explicit construction for these weak measurements. The measurement procedure has the structure of a random walk along a curve in state space, with the measurement ending when one of the end points is reached. This shows that any measurement can be generated by weak measurements, and hence that weak measurements are universal. This may have important applications to the theory of entanglement.