Advanced Tests and Applications of Quantum Nonlocality

量子非局域性的高级测试和应用

• 批准号: 1205870
• 负责人: Paul Kwiat
• 金额: $ 40.03万
• 依托单位: University of Illinois at Urbana-Champaign
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-08-15 至 2015-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1205870&HistoricalAwards=false
• 关键词: Advanced; Tests; Applications; Quantum; Nonlocality

Nonlocal entanglement has long been of great fundamental interest in quantum mechanics, and is now seen as a cornerstone in the nascent field of quantum information. However, although nearly half a century has passed since John Bell first showed that it was possible to perform a true, unambiguous test of the nonlocal, non-realistic aspects of quantum mechanics, such an unambiguous test has never been performed. Experimental tests of this quintessential quantum phenomenon have thus far been incomplete, all of them plagued by one or more "loopholes". We are addressing three main topics in advanced tests of quantum nonlocality. First, we employ new very efficient, fast detectors to realize an unambiguous test of nonlocality, a major quantum physics milestone. In the first phase, the "detection loophole" can be closed, which has never been done in optics; in the second phase, the "timing loophole" will also be closed, leading to the first truly loophole-free test of the nonlocal nature of reality. Realizing a system that can perform such a test is relevant for "verified" quantum random number generation and "device-independent" ultra-secure quantum cryptography systems, advantageous over traditional implementations because they do not rely on extra assumptions about the equipment being used. The second activity capitalizes on our recent NSF-funded successes in producing and controlling hyperentanglement -- photons that are simultaneously entangled in multiple degrees of freedom -- to study novel features of quantum nonlocality in larger Hilbert spaces. Specifically, using polarization, spatial-mode and time-bin entanglement, we explore states that reside in an unprecedented ~37,000,000-dimensional Hilbert space. In collaboration with University of Illinois colleague Prof. Anthony Leggett, we study the nonlocal character and robustness of the complex hyperentanglement in the face of decoherence, and as the dimensionality of the Hilbert space increases. Finally, using techniques developed here, we address two applications in the realm of advanced quantum information processing: realization of a completely verifiable source of quantum random numbers, and first implementation of a "device independent" quantum cryptography protocol. This project should lead to a number of other interesting investigations at the boundary between foundations of quantum mechanics and quantum information processing.One can hardly discuss the nature of reality without the notion of quantum entanglement -- ultrastrong-correlations between separated quantum systems -- in fact, entanglement is now seen as a cornerstone in the nascent field of quantum information. Therefore, testing it thoroughly is essential, if challenging. Our experiments will, once and for all, exclude all models of nature that rely on the intuitive principles of locality (there are no actions at a distance) and realism (things we measure have values before we measure them), as well as testing for the presence of correlations beyond those predicted by quantum mechanics. Should a "positive result" (i.e., an apparent breakdown of QM predictions) be found and confirmed, the eventual implications for our view of the physical world itself would be truly revolutionary. Moreover, the ability to study nonlocal correlations in much more complex quantum systems than has heretofore been possible -- using hyperentanglement -- may reveal new features in the robustness/fragility of entanglement phenomena. Finally, as part of the project, nonlocality experiments for undergraduate laboratories are being developed in collaboration with colleagues at undergraduate institutions, bringing the realities of quantum information phenomena to students at an earlier age and in broader venues.

非定域纠缠长期以来一直是量子力学的重要基础，现在被视为量子信息新兴领域的基石。然而，尽管自约翰·贝尔首次证明可以对量子力学的非定域性、非实在性进行真正的、明确的检验以来，已经过去了将近半个世纪，但这样一个明确的检验从未被进行过。到目前为止，对这种典型量子现象的实验测试还不完整，所有这些都受到一个或多个“漏洞”的困扰。我们正在解决量子非定域性高级测试中的三个主要问题。首先，我们采用新的非常有效，快速的检测器来实现非定域性的明确测试，这是量子物理学的一个重要里程碑。在第一阶段，“检测漏洞”可以被关闭，这在光学中是从来没有做过的;在第二阶段，“定时漏洞”也将被关闭，导致第一个真正无漏洞的现实非局部性质的测试。 实现可以执行这种测试的系统与“验证”量子随机数生成和“设备无关”超安全量子密码系统相关，优于传统实现，因为它们不依赖于关于所使用设备的额外假设。 第二项活动利用了我们最近NSF资助的在产生和控制超纠缠方面的成功-光子同时在多个自由度上纠缠-研究更大希尔伯特空间中量子非局域性的新特征。具体而言，使用偏振，空间模式和时间仓纠缠，我们探索了前所未有的~ 37，000，000维希尔伯特空间中的状态。在与伊利诺伊大学的同事安东尼·莱格特教授的合作中，我们研究了复杂超纠缠在退相干面前的非局部特征和鲁棒性，以及随着希尔伯特空间维数的增加。最后，使用这里开发的技术，我们解决两个应用领域的先进量子信息处理：实现一个完全可验证的量子随机数源，并首次实现了“设备独立”的量子密码协议。这个项目应该会在量子力学基础和量子信息处理之间的边界上引发许多其他有趣的研究。如果没有量子纠缠的概念--分离的量子系统之间的超强相关性--人们就很难讨论现实的本质。事实上，纠缠现在被视为量子信息新兴领域的基石。因此，如果具有挑战性，则彻底测试它是必不可少的。我们的实验将一劳永逸地排除所有依赖于定域性（在一定距离上没有作用）和实在性（我们测量的东西在我们测量它们之前就有了值）的直观原则的自然模型，以及测试量子力学预测之外的相关性的存在。 如果“阳性结果”（即，如果量子力学的预言被发现并得到证实，那么对我们对物理世界本身的看法的最终影响将是真正革命性的。此外，在比迄今为止更复杂的量子系统中研究非局域相关性的能力-使用超纠缠-可能揭示纠缠现象的鲁棒性/脆弱性的新特征。最后，作为该项目的一部分，正在与本科院校的同事合作开发本科实验室的非定域性实验，将量子信息现象的现实带给更早年龄和更广泛场所的学生。