Optical control and readout of spins in enriched 28Si for applications in quantum information

虽然量子力学原理是在近一个世纪前发现的，但人们越来越认识到，它们可能导致新的“量子技术”，在通信、安全和计算领域具有全新的、在某些情况下具有颠覆性应用的惊人潜力。在量子计算机（QC）中，叠加允许传统的比特（0或1）被两个状态的无限范围的叠加所取代，从而产生一个量子比特或量子位。量子比特可以通过纠缠连接起来，这样对一个量子比特的测量就会影响另一个量子比特的测量结果，即使它们完全分开。这违背了我们的直觉，因为它是基于宏观现实的，但可以完全用量子力学来解释。现在大家都知道，对于某些类型的重要问题，使用这些特性的QC可以比可以想象到的最大的传统计算机更强大、更快。这种范式转换的潜力正在推动世界各地的激烈研究，以找到一种技术，使质量控制足够复杂，以解决这类广泛的问题。广泛的系统正在被研究，从光子到原子再到亚原子粒子，如电子和核自旋。许多活动都集中在基于半导体的方法上，特别是涉及硅（Si），这是我们目前计算和信息技术的基础。如果能够开发出合适的量子比特以及制备、耦合和测量它们的方法，希望利用现有的硅材料和纳米级器件技术来构建QC。加拿大在这些领域有实力，包括滑铁卢的量子计算研究所，但我们是唯一一个专注于基于si的QI的备受瞩目的项目。加拿大目前也有唯一一家销售QC技术的公司，位于BC省本拿比的D-Wave系统公司。虽然D-Wave计算机基于量子退火，而不是最初设想的构建“通用”QC的算法方法，但它代表了加拿大科学和技术的一个非常重要的机会。我们发现富集的28Si具有独特的性质，即28Si中各种光学跃迁的线宽比普通Si（或任何其他半导体）中的线宽要尖锐得多，这导致了新的光学方法来控制和测量杂质的电子和核自旋，这些杂质是Si中量子比特的主要候选者。这些技术使我们能够测量相干时间——量子信息可以保持的时间——远远超过任何其他固态系统。我们最近利用实验室开发的光学方法，证明了室温下相干存储时间超过39分钟，比之前的记录长1000多倍。我们的研究结果和新方法正受到广泛关注，并为实现基于硅的质量控制技术而努力。拟议的项目将利用我们的成就和合作，并继续在这一领域设定新的方向。我们将证明我们的光学方法可以用于硅中的新中心，允许更大的复杂性，并测试重要的QI概念。我们将探索选择的系统，以利用硅中的自旋进行长期的、可从超导量子比特电路中检索的相干信息存储。我们还将研究其他类型的缺陷，这些缺陷有可能导致Si中QI的全新方法。该项目将培养具有半导体、光学、低温学和量子信息理论专业知识的未来领导者，他们将为实现量子技术的承诺做出贡献。

While the principles of quantum mechanics were discovered almost a century ago, there is a new and growing appreciation that they could lead to new ‘quantum technologies’ having spectacular potential for completely new and in some cases disruptive applications in communications, security, and computing. In a quantum computer (QC), superposition allows the conventional bit (0 or 1) to be replaced by an infinite range of superpositions of two states, giving a quantum bit, or qubit. Qubits can be linked using entanglement so that a measurement on one affects the outcome of a measurement on the other, even when they are completely separated. This defies our intuition, based as it is on macroscopic reality, but can be completely accounted for by quantum mechanics. It is now well understood that for certain classes of important problems, a QC using these properties could be enormously more powerful, and faster, than the largest imaginable conventional computer. This paradigm-shifting potential is fueling intense research around the world to find a technology for making a QC of sufficient complexity to solve this broad class of problems. A wide range of systems is being investigated, from photons to atoms to subatomic particles such as electrons and nuclear spins. Much activity is focused on semiconductor-based approaches, especially involving silicon (Si), which is the basis for our present computing and information technologies. It is hoped that the existing Si materials and nanoscale device technology could be harnessed to build a QC, if suitable qubits and the means of preparing, coupling and measuring them can be developed. Canada has strength in these areas, including the Institute for Quantum Computing in Waterloo, but ours is the only high-profile program focused on Si-based QI. Canada also has the only company currently selling QC technology, D-Wave Systems, of Burnaby BC. While the D-Wave computer is based on quantum annealing, and not the algorithmic approach first envisioned for constructing a ‘universal’ QC, it represents a very significant opportunity for Canadian science and technology. Our discovery that enriched 28Si has a unique property, namely, the linewidths of various optical transitions are much sharper in 28Si than in ordinary Si (or in any other semiconductor) led to new optical methods for controlling and measuring the electron and nuclear spins of impurities which are prime candidates for qubits in Si. These techniques have allowed us to measure coherence times - the time for which quantum information can be maintained - far beyond those of any other solid state system. We have recently used the optical methods developed in our lab to demonstrate coherent storage at room temperature for over 39 minutes – more than one thousand times longer than the previous record. Our results and new methods are receiving wide attention, and energizing an intense effort to realize a Si-based QC technology. The proposed program will capitalize on our achievements and collaborations, and continue to set new directions in this field. We will demonstrate that our optical methods can be used to work with new centers in Si allowing for greater complexity, and the testing of important QI concepts. We will explore systems selected for the possibility of using spins in Si for long term, retrievable storage of coherent information from superconducting qubit circuitry. We will also investigate other classes of defects that have the potential to lead to completely new approaches to QI in Si. This program will train future leaders, equipped with expertise in semiconductors, optics, cryogenics and quantum information theory, who will contribute to making the promise of quantum technologies a reality.