Department of Physics, University of Konstanz, D-78457 Konstanz, Germany.
Department of Physics, Princeton University, Princeton, New Jersey 08544, USA.
Phys Rev Lett. 2018 Oct 26;121(17):177701. doi: 10.1103/PhysRevLett.121.177701.
We propose a quadrupolar exchange-only spin qubit that is highly robust against charge noise and nuclear spin dephasing, the dominant decoherence mechanisms in quantum dots. The qubit consists of four electrons trapped in three quantum dots, and operates in a decoherence-free subspace to mitigate dephasing due to nuclear spins. To reduce sensitivity to charge noise, the qubit can be completely operated at an extended charge noise sweet spot that is first-order insensitive to electrical fluctuations. Because of on-site exchange mediated by the Coulomb interaction, the qubit energy splitting is electrically controllable and can amount to several GHz even in the "off" configuration, making it compatible with conventional microwave cavities.
我们提出了一种仅由四极交换作用产生的自旋量子比特，它对量子点中主要的退相干机制——电荷噪声和核自旋退相具有高度的鲁棒性。该量子比特由四个电子囚禁在三个量子点中组成，工作在一个无退相子空间中，以减轻由于核自旋引起的退相。为了降低对电荷噪声的敏感性，该量子比特可以完全在一个扩展的电荷噪声“甜蜜点”中操作，这个“甜蜜点”对电波动的一阶不敏感。由于库仑相互作用介导的局域交换作用，量子比特的能量分裂是电可控的，即使在“关闭”状态下也可以达到几 GHz，这使其与传统的微波腔兼容。
