论文标题
与LED泵的参数下转换中的极化纠缠
Polarization Entanglement from Parametric Down-Conversion with a LED Pump
论文作者
论文摘要
自发参数下转换（SPDC）是纠缠产生的可靠平台。通常，连贯的激光束是泵送非线性晶体的必要先决条件。在这里，我们通过使用商业发光二极管（LED）源用作泵束，从而打破了此障碍，以产生极化纠缠的光子对。这种效果是违反直觉的，因为LED源具有极低的空间连贯性，在下调过程中将其传递到Biphoton波函数。但是，II型相匹配条件自然会过滤LED光的特定频率和波长，以便参与SPDC，以便可以生成局部偏振状态，而不论整个横向平面上的全局不连贯性如何。在我们的实验中，我们表征了LED光诱导的极化纠缠的程度，这是违反贝尔不平等的标准框架。我们已经实现了铃铛值$ s = 2.33 \ pm 0.097 $，显然超过了经典的$ s = 2 $，因此见证了量子纠缠。我们的工作可以扩展以通过使用其他自然光源（例如阳光和生物灯）来制备极化纠缠，这有望有望在外层空间中无电量子通信。
Spontaneous parametric down-conversion (SPDC) is a reliable platform for entanglement generation. Routinely, a coherent laser beam is an essential prerequisite for pumping the nonlinear crystal. Here we break this barrier to generate polarization entangled photon pairs by using a commercial light-emitting diode (LED) source to serve as the pump beam. This effect is counterintuitive, as the LED source is of extremely low spatial coherence, which is transferred during the down-conversion process to the biphoton wavefunction. However, the type-II phase-matching condition naturally filters the specific frequency and wavelength of LED light exclusively to participate in SPDC such that localized polarization Bell states can be generated, regardless of the global incoherence over the full transverse plane. In our experiment, we characterize the degree of LED light-induced polarization entanglement in the standard framework of the violation of Bell inequality. We have achieved the Bell value $S=2.33\pm 0.097$, obviously surpassing the classical bound $S=2$ and thus witnessing the quantum entanglement. Our work can be extended to prepare polarization entanglement by using other natural light sources, such as sunlight and bio-light, which holds promise for electricity-free quantum communications in outer space.
