Advanced Photonic Quantum Information Processing

先进光子量子信息处理

• 批准号: 1520991
• 负责人: Paul Kwiat
• 金额: $ 10万
• 依托单位: University of Illinois at Urbana-Champaign
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-08-01 至 2017-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1520991&HistoricalAwards=false
• 关键词: Advanced; Photonic; Quantum; Information; Processing

The nascent field of quantum information promises amazing and important capabilities, such as ultra-secure encryption, ultra-fast computation, and ultra-precise metrology. Photons are excellent carriers of quantum information, having been employed in numerous groundbreaking quantum information processing experiments. However, although many approaches to realizing a reliable periodic source of single photons - a critical resource for quantum applications - are being pursued, to date none operates at a level sufficient for realizing scalable optical quantum information processing. To date, nearly all experiments have been limited by inefficient photon-pair sources and detectors. Consequently, for example, a protocol needing five photons would be the equivalent of rolling five die and getting a "6" on each one, with the likelihood of only (1/6)(1/6)(1/6)(1/6)(1/6)= 0.00013. By incorporating time multiplexing of the photon source - making multiple attempts (~20) until we get a successful output, the success probability to create five photons is increased in principle to 88%. Large-scale quantum information processing also requires highly efficient detectors and high-fidelity photonic circuits. This project will solve these needs, combining advanced technologies for periodic single-/multi-photon sources, integrated photonic waveguide circuits, and highly efficient single-photon detectors. The net result will be a new capability for optical quantum information processing, greatly exceeding what has been possible until now.The realization of an efficient periodic source of indistinguishable photons is an enabling technology for many quantum information protocols, including one-way quantum computing, improved quantum cryptography, and quantum metrology. It would immediately enhance almost all existing quantum communication protocols, simultaneously increasing the possible rate while reducing the deleterious effects of multi-photon events. Spontaneous parametric downconversion is well known as a source of heralded single photons - detecting one of the daughter photons indicates the presence of the other one. However, the downconversion process itself is probabilistic, and therefore the resulting single photons are not on-demand; furthermore, using a brighter pump pulse to increase the likelihood of producing a pair automatically increases the unwanted probability of producing more than one pair. By employing temporal multiplexing, allowing photons created in any one of, e.g., 50 time slots to be mapped onto a single final time window, the net efficiency for single-photon creation can be greatly enhanced, while minimizing the likelihood of unwanted multi-photon events. The benefit becomes even greater when intentionally trying to create states with many photons: the methods developed here could enable rate enhancements over five orders of magnitude (and for one experiment up to 12 orders!). A similar improvement in optical circuitry (with regard to size and stability) is realized using custom-fabricated waveguides written into low-loss glass. One key feature of this work is the collaboration with Israeli researcher Yaron Silberberg, who will develop the required photonic waveguide circuitry, and work with the group on the final set of applications. The technology of 'integrating' a large number of waveguides and optics such as beamsplitters and phase shifters into a tiny glass substrate (approximately cross 5 centimeter area) will provide enhanced stability and interference between multiple photons. Thus, the unique bi-national connection in this proposal enables the development and implementation of sophisticated quantum photonic systems well beyond those that have been possible to date, until now limited to only a few photons. Combining the new source with optimized photonic waveguide circuitry, the project will then investigate several interesting photon-based quantum effects, including potentially scalable optical quantum logic and quantum walks.

新生的量子信息领域承诺提供令人惊叹和重要的能力，如超安全加密、超快计算和超精密计量。光子是量子信息的优秀载体，已被用于众多突破性的量子信息处理实验。然而，尽管人们正在寻求实现可靠的周期性单光子源--量子应用的关键资源--的许多方法，但到目前为止，没有一种方法的运行水平足以实现可扩展的光学量子信息处理。到目前为止，几乎所有的实验都受到效率低下的光子对光源和探测器的限制。因此，例如，一个需要五个光子的协议将等同于滚动五个骰子并在每个骰子上得到一个“6”，可能性仅为(1/6)(1/6)(1/6)(1/6)=0.00013。通过引入光子源的时分复用-进行多次尝试(~20)直到我们获得成功的输出，成功创建五个光子的概率原则上增加到88%。大规模的量子信息处理还需要高效的探测器和高保真的光子电路。该项目将结合周期性单/多光子源、集成光子波导电路和高效单光子探测器的先进技术来解决这些需求。最终的结果将是光学量子信息处理的新能力，远远超过目前的可能。实现高效的周期不可分辨光子源是许多量子信息协议的使能技术，包括单向量子计算、改进的量子密码学和量子计量学。它将立即增强几乎所有现有的量子通信协议，同时提高可能的速率，同时减少多光子事件的有害影响。自发的参数下转换是众所周知的预告单光子的来源--检测子光子中的一个表明另一个的存在。然而，下转换过程本身是概率的，因此产生的单光子不是按需产生的；此外，使用更亮的泵浦脉冲来增加产生对的可能性会自动增加产生多个对的不必要的概率。通过采用时间多路复用，允许在例如50个时隙中的任何一个中创建的光子被映射到单个最终时间窗口上，可以大大提高单光子创建的净效率，同时最小化不想要的多光子事件的可能性。当有意尝试创建具有多个光子的状态时，好处变得更大：这里开发的方法可以使速率提高超过5个数量级(对于一个实验，最高可达12个数量级！)。使用写入低损耗玻璃的定制波导，实现了光学电路的类似改进(关于尺寸和稳定性)。这项工作的一个关键特征是与以色列研究人员Yaron Silberberg的合作，Yaron Silberberg将开发所需的光子波导电路，并与该团队合作开发最后一套应用程序。将大量的波导和光学器件(如分束器和移相器)“集成”到一个微小的玻璃基板(大约横跨5厘米的面积)中的技术将提供增强的稳定性和多个光子之间的干涉。因此，这项提议中独特的两国联系使复杂的量子光子系统的开发和实施远远超出了迄今为止可能实现的系统，到目前为止仅限于少数几个光子。将新光源与优化的光子波导电路相结合，该项目将研究几种有趣的基于光子的量子效应，包括潜在的可扩展光学量子逻辑和量子行走。