Time-to-digital converter for time-resolved multi-photon coincidence measurements

纠缠是标志着量子与经典世界最显著偏差的物理特性。从一个基本的观点来看，创造并将纠缠光子分布到遥远的地方的可能性是迷人的，因为它会导致基于局部现实理论的预测与基于量子力学的预测之间的可验证的矛盾（这种验证被称为“贝尔不等式”的测试）。另一方面，纠缠光子是量子隐形传态、量子中继器和量子网络的核心，它们允许使用量子密钥分发（QKD）进行加密密钥的可证明安全分发，并最终与未来的量子计算机之间进行量子通信。这种网络将确保政府部门内部和部门之间以及卫生和银行业、企业和个人之间的安全通信；允许一个人将一个计算任务发送到一个遥远的量子云计算机，而没有任何人——甚至计算机本身——能够学习这个任务；并产生真正令人难以置信的计算性能，例如快速找到“大海捞针”（例如在未排序的数据库中找到特定条目），用于机器学习（例如分析大数据），以及理解化学反应动力学（例如创建更好的药品和精炼石油产品）。我们的长期目标是建立一个全加拿大范围的量子网络。

Entanglement is the physical property that marks the most striking deviation of the quantum from the classical world. From a fundamental point-of-view, the possibility to create and distribute entangled photons to distant locations is fascinating because it leads to verifiable contradictions between predictions based on local realistic theories and those based on quantum mechanics (such verifications are known as tests of a “Bell-inequality”). On the other hand, entangled photons are at the heart of quantum teleportation, quantum repeaters and quantum networks, which allow the provably-secure distribution of encryption keys using quantum key distribution (QKD) and ultimately quantum communication with and between future quantum computers. Such a network will ensure secure communications within and between government departments and for the health and banking industries, businesses and individuals; allow one to send a computational task to a distant quantum cloud computer without anybody - not even the computer itself - being able to learn the task; and result in truly mind-boggling computational performance, e.g. for rapidly finding ‘a needle in a haystack’ (e.g. a specific entry in an unsorted database), for machine learning (e.g. for analyzing big data), and for understanding chemical reaction dynamics (e.g. to create better pharmaceuticals and refined petroleum products). Our long-term goal is the creation of a Canada-wide quantum network. This grant will allow purchasing a time-to-digital converter (TDC) for highly time-resolved coincidence measurements of detection signals created by up to eight single-photon detectors. The TDC is urgently required for near-future experiments with multiple entangled photon pairs that line the path towards a quantum network. Its timely acquisition will remove an important bottleneck that currently impacts further developments in the Tittel group: a limit in the maximum photon detection rate that our current TDCs can deal with; as well as the problem that our current devices start to deteriorate and may soon become dysfunctional. In addition to creating highly qualified personnel at various career levels and advancing the fields of quantum optics and quantum communication, our research, through the acquisition of this TDC, will ensure that Canada, after a lot of investment into quantum communication during the past decade, remains competitive in this important area.