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arXiv 1210.3085cond-mat.mes-hall
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碳纳米管中的谷自旋量子比特

A valley-spin qubit in a carbon nanotube

Edward A. Laird, Fei Pei, Leo. P. Kouwenhoven

摘要:

虽然III-V族半导体量子点中的电子自旋作为量子比特已经显示出很大的前景,但一个主要的挑战是这些材料中不可避免的超精细退相干。在IV族半导体中,主要的核物质是无自旋的,允许量子比特相干时间在金刚石和硅中延长到几秒。碳纳米管是一种特别有吸引力的主体材料,因为与谷自由度的自旋轨道相互作用允许量子位的电操纵。在这项工作中,我们实现了这样一个量子比特的纳米管双量子点。量子比特被编码在两个谷自旋态中,通过由纳米管中的弯曲介导的电驱动自旋共振(EDSR)进行相干操纵。通过测量泡利阻塞中的电流来执行读出。演示了任意量子比特的旋转,并通过哈恩回波测量了相干时间。虽然在我们目前的设备中测得的退相干时间仅为65 ns,但这项工作提供了创建量子位的可能性,可以几乎消除超精细相互作用。

英文摘要:

Although electron spins in III-V semiconductor quantum dots have shown great promise as qubits, a major challenge is the unavoidable hyperfine decoherence in these materials. In group IV semiconductors, the dominant nuclear species are spinless, allowing for qubit coherence times that have been extended up to seconds in diamond and silicon. Carbon nanotubes are a particularly attractive host material, because the spin-orbit interaction with the valley degree of freedom allows for electrical manipulation of the qubit. In this work, we realise such a qubit in a nanotube double quantum dot. The qubit is encoded in two valley-spin states, with coherent manipulation via electrically driven spin resonance (EDSR) mediated by a bend in the nanotube. Readout is performed by measuring the current in Pauli blockade. Arbitrary qubit rotations are demonstrated, and the coherence time is measured via Hahn echo. Although the measured decoherence time is only 65 ns in our current device, this work offers the possibility of creating a qubit for which hyperfine interaction can be virtually eliminated.

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