利用纯相位空间光调制器优化产生空间量子点
Optimized generation of spatial qudits by using a pure phase spatial light modulator
摘要：
本文提出了一种制备空间量子任意纯态的方法，即制备携带单光子横向动量和位置信息的D维（D > 2）量子系统。为此，一组具有复杂传输的D狭缝显示在空间光调制器（SLM）上。在最近的工作中，我们已经展示了一种方法，该方法需要单个纯相位SLM来独立地控制定义维度D的量子态的复系数。通过在每个狭缝内引入相位光栅编码振幅信息，并将复透射的相位值加到相位光栅上。在空间滤波过程之后，我们在图像平面中获得所需的量子态。虽然这种方法已被证明是一个很好的替代紧凑以前报告的架构，它提出了一些功能，可以改进。在本文中，我们提出了一种替代方案来编码所需的相位值，最大限度地减少与SLM相关的时间相位波动的影响，在此方案中，振幅由SLM寻址的适当相位光栅设置，而相对相位由这些相位光栅的横向位移获得。我们表明，这种方法提高了质量的准备状态，并提供了非常高的结晶度的任何状态的准备。该方案的另一个优点是通过将光栅移位一个周期来获得完整的2π调制，因此编码不受SLM实现的相位调制范围的限制。数值模拟，考虑到相位起伏，显示高的量子比特状态覆盖整个布洛赫球表面。对D = 3和D = 7的量子进行类似的分析。
英文摘要：
We present a method for preparing arbitrary pure states of spatial qudits, namely, D-dimensional (D > 2) quantum systems carrying information in the transverse momentum and position of single photons. For this purpose, a set of D slits with complex transmission are displayed on a spatial light modulator (SLM). In a recent work we have shown a method that requires a single phase-only SLM to control independently the complex coefficients which define the quantum state of dimension D. The amplitude information was codified by introducing phase gratings inside each slit and the phase value of the complex transmission was added to the phase gratings. After a spatial filtering process we obtained in the image plane the desired qudit state. Although this method has proven to be a good alternative to compact the previously reported architectures, it presents some features that could be improved. In this paper we present an alternative scheme to codify the required phase values that minimizes the effects of temporal phase fluctuations associated to the SLM where the codification is carried on. In this scheme the amplitudes are set by appropriate phase gratings addressed at the SLM while the relative phases are obtained by a lateral displacement of these phase gratings. We show that this method improves the quality of the prepared state and provides very high fidelities of preparation for any state. An additional advantage of this scheme is that a complete 2πmodulation is obtained by shifting the grating by one period, and hence the encoding is not limited by the phase modulation range achieved by the SLM. Numerical simulations, that take into account the phase fluctuations, show high fidelities for thousands of qubit states covering the whole Bloch sphere surface. Similar analysis are performed for qudits with D = 3 and D = 7.
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