Erbium implanted silicon for solid state quantum technologies

基于硅的信息技术已经彻底改变了现代世界。随着器件特征尺寸的减小，集成电路（IC）已经变得受制于量子力学现象。量子技术旨在利用这些量子力学现象来执行传统技术难以或不可能完成的任务。发展量子技术的主要障碍之一是在一个称为退相干的过程中，由于与环境的干扰而导致量子叠加态的快速破坏。最近，已经证明了使用少量具有“备用”电子（施主杂质）的硅添加剂的极长的相干时间（小时）。虽然原子在真空中可以获得更长的时间，但永久捕获在固体晶体（如硅）中的原子更容易处理。固体中退相干的一个主要来源是构成主晶体的原子的核自旋，因为它们经常不受控制地四处跳动。这已经通过同位素纯化硅（通常含有同位素的混合物，其中只有少数具有核自旋）来消除。即便如此，施主杂质不会与电信波长的光相互作用，这对许多量子技术，特别是量子通信方案至关重要。目前还没有具有长相干时间和光纤电信兼容性的固态量子技术平台。然而，稀土原子铒的光学跃迁与电信兼容。稀土离子也是量子技术的理想系统，因为其电子的屏蔽为退相干提供了原子尺度的屏障。当掺杂到相对高的核自旋金属氧化物晶体中时，稀土显示出与天然硅中的施主杂质相当的相干时间，但在硅本身中还有待研究。离子注入是当今硅IC制造中使用的一种众所周知的技术，历史表明，对新技术的商业兴趣有利于那些依赖于已建立的制造平台和技术的技术。考虑到使用铒注入同位素纯硅的相干时间的预期改善，应该可以开发具有长相干时间的量子技术平台，并且是电信和传统IC工具兼容的。量子计算方案需要量子比特（量子比特）的纠缠，这在硅基量子比特中仍然具有挑战性，但已在超导电路量子比特中得到证明。由于后者具有短的相干时间和缺乏光学寻址能力，我设想一种混合方案，其中处理与超导谐振器和铒注入硅量子比特被用作量子存储器元件和作为电信和微波波长光子之间的量子换能器。通过这个项目，我将向研究界介绍一个新的量子技术平台：铒注入硅。该平台结合了铒的电信能力和硅的集成电路能力，使其对量子计算和量子通信应用都很有价值。

Silicon based information technology has revolutionized the modern world. As device features have decreased in size, integrated circuits (ICs) have become subject to quantum mechanical phenomena. Quantum technologies aim to exploit these quantum mechanical phenomena to perform tasks that are difficult or impossible with conventional technologies. One of the main obstacles in developing quantum technologies is the rapid destruction of quantum superposition states caused by interference with the environment in a process called decoherence. Recently, extremely long coherence times (hours) have been demonstrated using small amounts of additives to silicon that have a "spare" electron (donor impurities). Although even longer times can be obtained for atoms in vacuum, an atom trapped permanently in a solid crystal such as silicon is much easier to handle. A major source of decoherence in solids is the nuclear spin of the atoms that make up the host crystals, as they often flop around uncontrollably. This has been eliminated by isotopically purifying the silicon (which normally contains a mix of isotopes, only a small number of which have nuclear spin). Even so, the donor impurities don't interact with telecoms wavelength light, and this is critical for many quantum technologies, quantum communication schemes in particular. There are currently no solid-state quantum technology platforms with long coherence times and optical fibre telecommunications compatibility. The optical transitions of the rare-earth atom erbium are, however, telecommunications compatible. Rare-earth ions are also ideal systems for quantum technologies because the shielding of their electrons offers an atomic scale barrier to decoherence. When doped into relatively high nuclear spin metal oxide crystals, rare-earths show coherence times comparable to donor impurities in natural silicon, but are yet to be investigated in silicon themselves. Ion implantation is a well understood technology used in today's silicon IC manufacture and history has shown that commercial interest in new technologies favours those relying on established fabrication platforms and techniques. Given the expected improvement in coherence time from using erbium implanted isotopically pure silicon, it should be possible to develop a quantum technology platform that has a long coherence time, and is telecommunications and conventional IC tooling compatible.Quantum computation schemes require the entanglement of quantum bits (qubits), this remains challenging in silicon based qubits but has been demonstrated in superconducting circuit qubits. As the latter has short coherence times and lacks optical addressability, I envisage a hybrid scheme where processing is performed with the superconducting resonators and erbium implanted silicon qubits are used as the quantum memory element and as a quantum transducer between telecommunications and microwave wavelength photons. Through this project I will introduce a new quantum technology platform to the research community: erbium implanted silicon. This platform combines the telecommunication capability of erbium and integrated circuit capability of silicon, making it valuable for both quantum computing and quantum communication applications.