Hilbert space engineering in 4f single-molecule magnets on superconducting sur- faces

单个磁性离子的电子自旋具有用作量子比特（qubit）的潜力。特别是，4f离子在单分子磁体（SMM）已显示出非常长的弛豫时间接近小时的时间尺度在低温下。在以电子方式访问的固态器件中，电子自旋需要耦合到引线的传导电子，以便允许准备和读出自旋状态。然而，与接触的电子气的相互作用可能导致自旋的弛豫、退相干甚至近藤屏蔽。最近，晶体场对称性和超精细相互作用对4f离子核的作用已经被研究，以避免弛豫。在这个提议中，这种方法的下一个逻辑步骤不仅要抑制弛豫，还要防止退相干并提高潜在量子位的相干时间。我们将设计和合成同位素纯金属有机分子与稀土离子在配位场的四重或更高的对称性，以保护磁化隧穿和存款这些单晶和超导表面。晶体场的对称性将被用来设计希尔伯特空间，以禁止电子自旋翻转散射以及核自旋翻转。此外，超导间隙将抑制电子在差距内的弹性散射。在第一步中，弛豫时间将研究预期的磁电报噪声与自旋极化扫描隧道显微镜在25 mK测量。由超精细相互作用驱动的跃迁可以导致在特定的外加磁场下的磁化隧穿，如电报噪声中所证明的。 相干时间将通过耦合两个磁性离子进行研究，这样拉比振荡应该出现。

The electronic spins of single magnetic ions have the potential to be used as quantum bits (qubits). Especially, 4f ions in single molecular magnets (SMMs) have shown very long relaxation times approaching time scales of hours at low temperatures. In solid state devices that are accessed electronically, the electronic spins need to be coupled to the conduction electrons of the leads in order to allow preparation and read out of the spin state. The interaction with the electron gas of the contacts, however, may lead to relaxation, decoherence or even Kondo screening of the spin. Recently, the role of crystal field symmetries and the hyperfine interaction to the nucleus of the 4f ions has been studied in ways to avoid relaxation. In this proposal, the next logical step in this approach will be taken to not only suppress relaxation but also to prevent decoherence and boost coherence times of the potential qubits. We will design and synthesize isotopologically pure metal-organic molecules with rare earth ions in ligand fields of four-fold or higher symmetries in order to protect magnetization tunneling and deposit these onto single crystalline and superconducting surfaces. The symmetry of the crystal field will be used to design the Hilbert space in order to forbid electron spin-flip scattering as well as nuclear spin flips. In addition, the superconducting gap will inhibit elastic scattering of electrons within the gap. In a first step, relaxation times times will be studied by the expected magnetic telegraph noise as measured with spin-polarized scanning tunneling microscopy at 25 mK. Transitions driven by hyperfine interaction can lead to magnetization tunneling at specific applied magnetic fields as evidenced in the telegraph noise. Coherence times will be investigated by coupling two magnetic ions such that Rabi oscillations should appear.