Decoherence spectroscopy with individual two-level tunneling defects.
Decoherence spectroscopy with individual two-level tunneling defects.
复制标题
DOI：
10.1038/srep23786
复制
发表时间：
2016-03-31
影响因子：
4.6
通讯作者：
Ustinov AV
中科院分区：
文献类型：
--
作者：
Lisenfeld J;Bilmes A;Matityahu S;Zanker S;Marthaler M;Schechter M;Schön G;Shnirman A;Weiss G;Ustinov AV
微制造量子器件的最新进展表明，一个无处不在的噪声源起源于隧穿材料缺陷，导致寄生二能级系统（TLS）的稀疏浴。对于超导量子比特，存在于电极表面和隧道结中的TLS是退相干的主要部分，因此对实现固态量子处理器构成了严重的障碍。在这里，我们利用超导量子比特来探索相干操作的TLS的量子态演化，以揭示其各自的属性和环境相互作用的新的光。我们确定了TLS能量弛豫速率的频率依赖性，可以解释为耦合到声子模式，而不是预期的相互TLS相互作用。大多数研究的TLS被发现是免费的纯退相在其能量简并点，其拉姆齐和自旋回波退相率的规模线性和二次非对称能量，分别。我们提供了一个基于标准隧穿模型的解释，并确定与非相干低频（热）TLS的相互作用作为相干高频TLS中纯退相的主要机制。
Recent progress with microfabricated quantum devices has revealed that an ubiquitous source of noise originates in tunneling material defects that give rise to a sparse bath of parasitic two-level systems (TLSs). For superconducting qubits, TLSs residing on electrode surfaces and in tunnel junctions account for a major part of decoherence and thus pose a serious roadblock to the realization of solid-state quantum processors. Here, we utilize a superconducting qubit to explore the quantum state evolution of coherently operated TLSs in order to shed new light on their individual properties and environmental interactions. We identify a frequency-dependence of TLS energy relaxation rates that can be explained by a coupling to phononic modes rather than by anticipated mutual TLS interactions. Most investigated TLSs are found to be free of pure dephasing at their energy degeneracy points, around which their Ramsey and spin-echo dephasing rates scale linearly and quadratically with asymmetry energy, respectively. We provide an explanation based on the standard tunneling model, and identify interaction with incoherent low-frequency (thermal) TLSs as the major mechanism of the pure dephasing in coherent high-frequency TLS.