Zadrozny Joseph M, Freedman Danna E
Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States.
Inorg Chem. 2015 Dec 21;54(24):12027-31. doi: 10.1021/acs.inorgchem.5b02429. Epub 2015 Dec 9.
High-spin transition metal complexes are of interest as candidates for quantum information processing owing to the tunability of the pairs of MS levels for use as quantum bits (qubits). Thus, the design of high-spin systems that afford qubits with stable superposition states is of primary importance. Nuclear spins are a potent instigator of superposition instability; thus, we probed the Ph4P(+) salt of the nuclear spin-free complex Fe(C5O5)3 (1) to see if long-lived superpositions were possible in such a system. Continuous-wave and pulsed electron paramagnetic resonance (EPR) spectroscopic measurements reveal a strong EPR transition at X-band that can be utilized as a qubit. However, at 5 K the coherent lifetime, T2, for this resonance is 721(3) ns and decreases rapidly with increasing temperature. Simultaneously, the spin-lattice relaxation time is extremely short, 11.33(1) μs, at 5 K, and also rapidly decreases with increasing temperature. The coincidence of these two temperature-dependent data sets suggests that T2 in 1 is strongly limited by the short T1. Importantly, these results highlight the need for new design parameters in pursuit of high-spin species with appreciable coherence times.
由于用作量子比特（qubit）的MS能级对具有可调谐性，高自旋过渡金属配合物作为量子信息处理的候选物备受关注。因此，设计能够为量子比特提供稳定叠加态的高自旋系统至关重要。核自旋是叠加态不稳定性的一个有力诱因；因此，我们对无核自旋配合物Fe(C5O5)3（1）的Ph4P(+)盐进行了探究，以考察在这样一个系统中是否可能存在长寿命叠加态。连续波和脉冲电子顺磁共振（EPR）光谱测量揭示了在X波段有一个强EPR跃迁，可将其用作量子比特。然而，在5 K时，该共振的相干寿命T2为721(3) ns，并随温度升高而迅速降低。同时，自旋晶格弛豫时间在5 K时极短，为11.33(1) μs，也随温度升高而迅速降低。这两个与温度相关的数据集的吻合表明，1中的T2受到短T1的强烈限制。重要的是，这些结果凸显了在寻求具有可观相干时间的高自旋物种时需要新的设计参数。
