Scaling Up quantum computation with Molecular spins

SUQMO旨在为量子计算和模拟的新架构奠定基础，其中信息被编码在捕获在分子中的自旋量子位中，这些分子通过与超导谐振器的耦合被读出和通信。该技术具有很高的鲁棒性和可扩展性潜力，基于分子构建块的微观和完全可再现的性质以及在每个构建块中包含多个量子位的可能性，这提供了额外的维度来增加计算资源并实现容错逻辑量子位。该提案侧重于两个具体目标，这是实现这种磁量子处理器的关键里程碑。第一个是在分子结构中实现量子纠错码。第二个是在单个分子自旋和被困在共振器中的单个光子之间实现强耦合或相干耦合。实现这些目标的进展涉及不同学科之间以及实验和理论方法之间的协调合作。将结合配位和超分子化学来设计和合成承载多个量子比特的分子结构。这些系统的自旋弛豫T1和相干T2时间将通过最先进的电子顺磁光谱测量，并通过化学方法优化到超过100微秒的值，这是克服纠错相干阈值和实现与超导谐振器的强耦合所需的。新一代的微波超导纳米谐振器，能够挤压微波磁场到纳米级区域，将通过铣削下的中心传输线与离子束纳米光刻或通过制造纳米桥与单壁碳纳米管或二维超导层。分子将通过蘸笔纳米光刻和使用表面反应分子配体的组合被纳米图案化到这些设备中。利用STM泵浦-探测实验，在低温下测定了单个分子与超导衬底的相干时间。最终目标是对单个分子自旋进行电路QED实验，以实现强耦合机制，提供基本量子操作的概念验证实现并读出它们的量子自旋态。

SUQMO aims to set the basis of a new architecture for quantum computation and simulation, in which information is encoded in spin qubits trapped in molecules that are read-out and communicate via their coupling to a superconducting resonator. This technology has a high potential for robustness and scalability, based on the microscopic and perfectly reproducible nature of the molecular building blocks and on the possibility of embodying multiple qubits in each of them, which provide an extra dimension to increase computational resources and to implement fault-tolerant logical qubits. The proposal focuses on two specific targets, which represent crucial milestones for the realization of such magnetic quantum processor. The first is the implementation of quantum error correction codes in molecular structures. The second is the attainment of strong, or coherent, coupling between an individual molecular spin and a single photon trapped in a resonator. Progress towards these targets involves a coordinated cooperation between diverse disciplines and between experimental and theoretical methods. Coordination and supramolecular chemistry will be combined to design and synthesize molecular structures hosting multiple qubits. Spin relaxation T1 and coherence T2 times of these systems will be measured by state-of-the-art electron paramagnetic spectroscopy and optimized, by means of chemical methods, to values exceeding 100 microseconds that are required both to overcome the error correction coherence thresholds and attain strong coupling to a superconducting resonator. A new generation of microwave superconducting nanoresonators, able to squeeze microwave magnetic fields into nanoscopic regions, will be developed by either milling down the central transmission line with ion-beam nanolithography or by fabricating nanobridges with single-wall carbon nanotubes or two-dimensional superconducting layers. Molecules will be nanopatterned into these devices by a combination of dip-pen nanolithography and the use of surface-reacting molecular ligands. Coherence times of individual molecules bond to superconducting substrates will be determined at low temperatures by STM-based pump-probe experiments. The final goal is to perform circuit QED experiments on individual molecular spins to achieve the strong coupling regime, provide proof-of-concept implementations of basic quantum operations and read-out their quantum spin states.