CAREER: Using Astronomy to Improve Tests of Quantum Mechanics

量子力学是一种理论，它支配着非常小的光，包括被称为光子的单个光粒子。一对光子可以以某种方式进行协调，因此，在某些情况下，测量它们中的每一个往往会得到相同的结果，而在另一些情况下，会得出相反的结果。光子可以表现出的这种无法用经典(非量子)方法模拟的高水平配位被称为纠缠。除了具有非常重要的基本意义外，这种协调还构成了量子密码学和量子计算等新兴技术的基础，因此在最极端的条件下探索这种协调的任何极限是很重要的(字面意思是)。该项目将使用首席研究员为早期量子测试开发的硬件来记录来自脉冲星的单个光子到达的时间，脉冲星是快速旋转的中子星，具有极强的磁场，在电磁光谱中产生辐射束。仔细的测量将揭示脉冲星发射背后的各种模型，并提供对爱因斯坦广义相对论某些方面的测量。所有这些实验都涉及与本科生一起定制电子产品，作为该项目的一部分，首席研究员将对学院理科专业的电子实验室课程教学方式进行现代化改造。学生每周都会主动参与设计，而不是被动地分析、构建、调试和记录标准电路的结果。这个角色将从小的、定义明确的设计任务开始，但将故意扩大到一个开放式的最终项目。许多研究小组将受益于新的或改进的仪器，从科学部门的研究人员那里征集的小型仪器项目将构成建议的最终项目清单的核心。在对量子力学纠缠粒子进行贝尔不等式测试时，以一种无法预测或受纠缠粒子的来源或其他粒子影响的方式为每个粒子选择测量基础是非常重要的。这位首席研究人员在该领域的独特贡献是利用天文来源改进了贝尔不等性的测试：既有我们银河系中的恒星，也有遥远星系中心的类星体，这些星系在宇宙只有今天十分之一的年龄时发出了自己的光。这个项目继续使用类星体作为测量设置的来源，如果不能访问这些类星体过去的光锥，就无法预测其序列。这将改进延迟选择实验和量子擦除测试，降低局部因果方案可以解释观察到的现象的可能性。这个项目包括建造一个萨格纳克干涉仪，作为一个明亮而纯粹的纠缠光子源。利用一种新的双旋转波片技术，将实时测量和优化产生的纠缠的质量。这个纠缠源将被带到天文天文台，并用于执行惠勒延迟选择实验的一个版本，其中来自遥远类星体的信息有效地插入或移除分束器。它还将被用作量子擦除测试的一部分，在量子擦除测试中，擦除或不擦除哪条路径信息的决定将不是由本地决定，而是由来自遥远类星体的光决定。这两个实验都会限制对观察到的量子现象的局部因果解释。同样的类星体记录硬件将被用于进行时间分辨偏振测量和亚纳秒精度的粗略光谱入库。与首席研究员在蟹状脉冲星上的工作类似，这个改进的装置将通过限制不同能量和偏振的光子之间的到达时间差异来限制爱因斯坦的弱等效原理。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Quantum Mechanics is the theory that governs the very small, including individual particles of light called photons. A pair of photons can coordinate in certain ways, such that measuring each of them tends to give the same result under some conditions and opposite results under others. This high level of coordination that photons can exhibit, which cannot be simulated by classical (non-quantum) means, is called entanglement. In addition to being of great fundamental importance, this coordination forms the basis for the emerging technologies of quantum cryptography and quantum computing, so it is important to probe for any limits of this coordination in the most extreme conditions over (literally) astronomical distances. This project will use the hardware developed by the principal investigator for earlier quantum tests to record the time of arrival of individual photons from pulsars, which are fast-spinning neutron stars with extremely strong magnetic fields that produce beams of radiation across the electromagnetic spectrum. Careful measurements will shed light on various models behind pulsar emission and provide measurements of certain aspects of Einstein’s General relativity. All of these experiments involve building custom electronics with undergraduates, and as part of this project, the principal investigator will modernize the way the electronics lab course is taught to the college’s science majors. Rather than passively analyzing, building, debugging, and recording results from standard circuits, students will take an active role in design each week. This role will start with small, well-defined design tasks, but will deliberately scale up to an open-ended final project. Many research groups would benefit from new or improved instrumentation, and small instrumentation projects solicited from researchers across the science departments will form the core of the list of suggested final projects.It is very important in performing tests of Bell’s Inequality on quantum-mechanically entangled particles to choose the measurement basis for each particle in a way that cannot be predicted or influenced by the source of entangled particles or by the other particle. The principal investigator’s unique contribution to the field has been to improve tests of Bell’s Inequality using astronomical sources: both stars in our own galaxy and quasars at the heart of distant galaxies that emitted their light when the universe was only a tenth as old as it is today. This project continues to use quasars as a source of measurement settings whose sequence cannot be predicted without having access to the past lightcones of those quasars. This will improve delayed-choice experiments and tests of quantum erasure, reducing the plausibility that locally-causal schemes can explain the observed phenomena. This project involves building a Sagnac interferometer as a bright and pure source of entangled photons. The quality of the resulting entanglement will be measured and optimized in real time with a novel dual rotating waveplate technique. This entanglement source will be brought to an astronomical observatory and used to perform a version of Wheeler’s delayed-choice experiment where information coming from a distant quasar effectively inserts or removes a beam splitter. It will also be used as part of a test of quantum erasure, where the decision to erase or not erase which-path information will be determined not locally, but by light from a distant quasar. Both of these experiments would put constraints on locally-causal explanations for the observed quantum phenomena. The same quasar-recording hardware will be used to do time-resolved polarimetry and coarse spectral binning with sub-nanosecond precision. Similar to the principal investigator’s work on the Crab pulsar, this improved device will set limits on Einstein’s Weak Equivalence Principle by constraining the difference in arrival times between photons of different energies and polarizations.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.