A novel source of quantum light: harnessing cascaded downconversion as a resource for quantum technologies

第一次量子革命是由量子物理的发现推动的，帮助我们了解了世界是如何运作的，并导致了计算机芯片和激光的发展。我们目前正处于第二次量子革命的边缘，这场革命将来自从根本上设计的直接利用量子现象的技术。这些技术有望通过量子处理器为某些任务提供相对于当今计算机的指数加速，从而改变计算。它们还将给计量和传感带来革命性的变化，传感器突破当前技术的灵敏度限制，以及密码学，量子协议能够提供绝对安全的通信。对几种量子技术的一个关键要求是有可用的实用方法来产生具有量子属性的光。光具有能够有效保存和传输量子数据的优势，使量子光源成为光学量子计算机的关键技术。光也是唯一真正可行的远距离快速传输量子数据的方法；因此，量子光源是量子通信和量子互联网发展的基本要求。在过去的几年里，我的团队探索了一种产生量子光的新方法--级联下转换--如何被用作各种量子信息应用的使能资源，并作为探索基本量子物理的工具。我们的努力卓有成效，取得了许多重大发现。虽然这些结果最终证明了级联下变频对基本和技术应用的相关性，但仍然存在一些障碍，阻碍了其广泛应用于实际用途。最重要的是，这种方法目前的效率很低，因为即使是最有效的非线性晶体，也只能转换一百万个光子中的一个。这限制了级联向下转换到不足以满足大多数真实世界场景的生产率。有了这项新的发现拨款，我提出了一个研究计划，旨在利用级联下转换的潜力进行量子信息处理。这将通过旨在解决与这一过程相关的当前挑战的技术开发，以及通过展示其在实施各种光学量子信息协议和应用方面的有用性来实现。这项研究计划将使加拿大人受益匪浅。首先，通过在加拿大蓬勃发展的量子部门产生与之直接相关的知识和新技术。其次，通过培训学生和其他高素质人员，为他们提供成为这一新的加拿大量子行业积极参与者所需的技能，该行业目前迫切需要熟练工人。

The first quantum revolution, spurred by the discovery of quantum physics, helped us understand how the world works and led to the development of computer chips and lasers. We are currently on the verge of a second quantum revolution, which will come from technologies designed from the ground up to directly exploit quantum phenomena. Such technologies are expected to transform computing, through quantum processors providing, for certain tasks, exponential speedups relative to today's computers. They will also revolutionize metrology and sensing, with sensors breaking through the sensitivity limits of current technologies, and cryptography, with quantum protocols able to provide absolutely secure communications. A critical requirement for several quantum technologies is the availability of practical methods to produce light possessing quantum properties. Light has the advantage of being able to hold and transfer quantum data effectively, making quantum light sources a key technology for optical quantum computers. Light is also the sole truly feasible method of transferring quantum data quickly over long distances; quantum light sources are therefore an essential requirement for quantum communication and for the development of the quantum internet. Over the last few years, my group has explored how a novel method of producing quantum light, cascaded downconversion, can be used as an enabling resource for various quantum information applications and as a tool to explore fundamental quantum physics. Our efforts have been extremely fruitful, leading to many significant discoveries. While these results conclusively demonstrate the relevance of cascaded downconversion for both fundamental and technological applications, certain roadblocks remain, preventing its widespread adoption for practical use. Most importantly, the method currently suffers from low efficiencies, as even the most efficient nonlinear crystals only convert one out of every million photons. This has limited cascaded downconversion to production rates insufficient for most real-world scenarios. With this new Discovery Grant, I propose a research program aimed at harnessing the potential of cascaded downconversion for quantum information processing. This will be done both through technical developments aimed at addressing the current challenges associated with the process, and by demonstrating its usefulness in implementing a variety of optical quantum information protocols and applications. This research program will be of significant benefit to Canadians. First, through the generation of knowledge and novel technologies of immediate relevance in the burgeoning Canadian quantum sector. Second, by training students and other highly qualified personnel to provide them with the skills required to be active participants in this new Canadian quantum industry which is currently in dire need of skilled workers.