Single photon detection for experimental quantum gravity

量子力学(QM)和广义相对论(GR)是20世纪最成功和最深刻的理论。除了对自然运作的洞察之外，它们还影响着我们的生活，从医学或智能手机的量子技术到GPS导航。然而，如何将广义相对论与量子力学结合起来，目前尚不清楚。在我们卡迪夫大学的实验室里，我们的目标是对量子力学(QM)和广义相对论(GR)之间的基本冲突进行首批经验探索之一。[1]自2019年以来，我们一直在调试一台仪器，使用最先进的量子技术增强的精密激光干涉仪来探测量子时空的对称性和基本原理。在接下来的几年里，我们将致力于一种新的设计，首次将来自相反系统的技术-LIGO和GEO600的高功率计量学-与超导纳米线单光子探测器(SNSPD)读出-结合在一起，以实现灵敏度的重大飞跃，超过可能探测量子化时空所需的理论预测水平。我们的新设计将使用光学滤光腔在载波光子的“干草堆”中找到几个“针”--信号光子，在受到量子时空涨落的扰动后具有不同的频率。你将致力于滤光腔的设计、建造和“工作”，滤光腔拒绝常规的载流子光子，但让罕见的信号光子通过，然后由单光子探测器进行计数。这是一个处于技术可能性边缘的项目，是学习光学工程技术、数字控制和噪声分析的一个令人兴奋的机会。您将在面向团队的环境中工作，但您有自己的项目，该项目嵌入到更大的实验设置中。所有相关技术在工业上都是高度适用的，但在这里用于令人兴奋的新物理探索。发现时空的颗粒性将为量子引力理论提供强有力的线索，并开辟实验量子引力的领域。

Quantum mechanics (QM) and general relativity (GR) are the most successful and profound theories of the 20th century. Beyond their insight into the workings of nature, they impact our lives from quantum technology in medicine or smartphones to GPS-guided navigation. It is not known though, how to combine General Relativity with quantum mechanics. In our laboratory at Cardiff University we aim to conduct one of the first empirical probes of the foundational conflict between quantum mechanics (QM) and general relativity (GR). [1]We have been commissioning an instrument since 2019 to probe the symmetries and foundational principles of quantum space-time using precision laser interferometers enhanced with state-of-the-art quantum technology. Over the next years, we will work on a new design that brings together for the first time technologies from opposite regimes - the high-power metrology of LIGO and GEO600 with superconducting nanowire single-photon detector (SNSPD) readout - to achieve a significant leap in sensitivity, surpassing the theoretically predicted levels necessary for a possible detection of quantized space-time. Our new design will use optical filter cavities to find a few "needles" - signal photons, which have different frequencies after being perturbed by quantum space-time fluctuations - in a "haystack" of carrier photons. You will work on the design, building, and "making to work" of optical filter cavities which reject the regular carrier photons, but let pass the rare signal photons which then get counted by the single-photon detectors.This is a project at the edge of technical possibility and an exciting opportunity to learn optical engineering techniques, digital controls, and noise analysis. You will work in a team-oriented environment but have your own project, which is embedded in a larger experimental setup. All the relevant techniques are highly applicable in industry, but are used here for the exciting search for new physics. Finding the graininess of space-time would give a powerful hint for a theory of quantum gravity and open up the field of experimental quantum gravity.