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非凡的努力。然而，潜在的难以克服的挑战可能迫在眉睫，例如，缺乏可伸缩性，缺乏可裁剪性，以及缺乏量子比特的定位能力。在OPTRIBITS中，我们将利用顺磁分子的基本优势，将其用作量子技术中基于自旋的量子比特。分子已被证明具有长达毫秒的系综相干时间，品质因数超过10,000。分子的大小是纳米级的，可以高密度地集成到设备中，从而实现量子设备的微型化。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，使它们能够适应特定的量子技术目标。由于在少数几个量子比特或有序排列中具有高度的量子比特可定位性，因此量子比特之间的相互作用可以被精确地控制，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一实体读出。因此，关于分子量子比特的绝大多数结果都是通过集合测量获得的，这些测量具有大量相同的量子比特副本。这一提议旨在通过发展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，光寻址已被充分证明允许单实体读出。为此，我们将设计、制备和研究健壮的分子量子比特，这种量子比特具有自旋态，可以通过光学泵浦来诱导自旋极化，并且具有很强的发光能力，可以进行光学读出。在第二步，我们将致力于通过将量子位结构固定在金表面上或通过创建与碳纳米材料的混合结构来实现设备集成。

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.