Optically Addressable Trityl-Radical-Based Molecular Qubits

人们普遍认为，量子技术将在不久的将来从根本上改变社会，人们正在为实现这一目标付出巨大的努力。然而，潜在的无法克服的挑战可能隐约出现，例如，缺乏可扩展性、缺乏可定制性以及缺乏量子位定位性。在OPTRIBITS中，我们将利用顺磁分子的基本优势，将其应用于量子技术中的自旋量子位。分子已经被证明具有长的整体相干时间，达到毫秒级，品质因数超过10，000。分子的尺寸是纳米级的，允许以高密度集成到器件中，从而实现量子器件的小型化。分子在自旋值、自旋能级结构和激发态性质方面是高度可定制的，使得它们能够适应特定的量子技术目标。由于在少数量子位或有序排列中量子位的高度可定位性，量子位间的相互作用可以被精细地控制，从而导致定义良好的相互作用。阻碍分子量子比特广泛使用的主要问题是缺乏方便的单实体读出。因此，分子量子比特的绝大多数结果都是通过具有大量相同量子比特副本的系综测量获得的。该提案旨在通过开发光学可寻址的分子量子比特来消除这一缺点。由于光学探测器的单光子灵敏度，已经充分证明了光学寻址允许单实体读出。为此，我们将设计，制备和研究鲁棒的分子量子比特，其具有允许通过光泵浦诱导自旋极化的自旋状态，并且高度发光以允许光学读出。在第二步中，我们将通过将量子位架构固定在金表面上或通过使用碳纳米材料创建混合结构来实现器件集成。

Quantum technologies are widely believed to fundamentally change society in the near future and extraordinary effort is being expended towards this goal. However potentially insurmountable challenges may loom on the horizon, e.g., lack of scalability, lack of tailorability and lack of qubit positionability. In OPTRIBITS, we will exploit the fundamental advantages of paramagnetic molecules for application as spin-based qubits in quantum technologies. Molecules have been shown to possess long ensemble coherence times up to the millisecond regime, with figures of merit exceeding 10,000. Molecules are nanoscopic in size, allowing for integration into devices at high densities enabling miniaturization of quantum devices. Molecules are highly tailorable in terms of spin values, spin level structures, and excited state properties, enabling their adaptation to specific quantum technological objectives. Interqubit interactions can be exquisitely controlled, due to the high degree of qubit positionability in few-qubit or ordered arrangements, leading to well-defined interactions. The main issue preventing the widespread use of molecular qubits has been the lack of convenient single-entity readout. As a result, the vast majority of results on molecular qubits have been obtained by ensemble measurements featuring large numbers of identical qubit copies. This proposal aims to remove this drawback by developing optically addressable molecular qubits. Optical addressing has been amply demonstrated to allow single-entity readout because of the single-photon sensitivity of optical detectors. To this end, we will design, prepare and study robust molecular qubits, which have spin states that allow for inducing spin polarization by optical pumping and are highly luminescent to allow for optical readout. In a second step, we will work towards device integration by immobilizing the qubit architectures on gold surfaces or by creating hybrid structures with carbon nanomaterials.