论文标题
量子测量理论的指针
Pointers for Quantum Measurement Theory
论文作者
论文摘要
在原子自旋-1/2或光子极化的标志性测量中，一种采用了两个空间分离和非相互作用的检测器。每个检测器是二进制的，记录了原子或光子的存在或不存在。对于$ D $状态粒子的测量，我们通过用一系列此类探测器替换熟悉的指针变量来重塑标准的Von Neumann测量形式主义，每个探测器的每一个都可能结果。我们表明，预生产过程的统一动力学将检测器输出限制为单个结果的子空间，因此指针从设备中出现。我们提出了该设备的物理扩展，该设备将每个检测器替换为辅助设备的Ancilla量子量子。这明确将指针分为不同的量子和（有效）经典部分，并将量子延迟到经典过渡。结果，人们不仅恢复了普通设备的崩溃情景，而且还可以观察到量子指针状态的叠加。
In the iconic measurements of atomic spin-1/2 or photon polarization, one employs two spatially separated and noninteracting detectors. Each detector is binary, registering the presence or absence of the atom or the photon. For measurements on a $d$-state particle we recast the standard von Neumann measurement formalism by replacing the familiar pointer variable with an array of such detectors, one for each of the $d$ possible outcomes. We show that the unitary dynamics of the premeasurement process restricts the detector outputs to the subspace of single outcomes, so that the pointer emerges from the apparatus. We propose a physical extension of this apparatus which replaces each detector with an ancilla qubit coupled to a readout device. This explicitly separates the pointer into distinct quantum and (effectively) classical parts, and delays the quantum to classical transition. As a result, one not only recovers the collapse scenario of an ordinary apparatus, but one can also observe a superposition of the quantum pointer states.
