用于微观隧道系统的量子传感器
Quantum Sensors for Microscopic Tunneling Systems
摘要：
玻璃的异常低温特性来自于固有的可激发实体，即所谓的隧穿两级系统（TLS），其微观性质几十年来一直困扰着固态物理学家。TLS对于诸如超导量子比特之类的微制造量子设备变得特别重要，因为它们是退相干的主要来源。在这里，我们提出了一种方法来表征个人TLS在几乎任意的材料作为薄膜沉积。该材料被用作电容器中的电介质，该电容器分流超导量子位的约瑟夫森结。在这样的混合量子系统中，量子比特充当检测和控制单个TLS的接口。我们演示了TLS共振的光谱测量，评估它们与外加应变和直流电场的耦合，并找到了样品材料中相干TLS之间强相互作用的证据。我们的方法为量子材料光谱学开辟了途径，以研究隧道缺陷的结构，并开发出超导量子计算机发展所迫切需要的低损耗超导体。
英文摘要：
The anomalous low-temperature properties of glasses arise from intrinsic excitable entities, so-called tunneling Two-Level-Systems (TLS), whose microscopic nature has been baffling solid-state physicists for decades. TLS have become particularly important for micro-fabricated quantum devices such as superconducting qubits, where they are a major source of decoherence. Here, we present a method to characterize individual TLS in virtually arbitrary materials deposited as thin-films. The material is used as the dielectric in a capacitor that shunts the Josephson junction of a superconducting qubit. In such a hybrid quantum system the qubit serves as an interface to detect and control individual TLS. We demonstrate spectroscopic measurements of TLS resonances, evaluate their coupling to applied strain and DC-electric fields, and find evidence of strong interaction between coherent TLS in the sample material. Our approach opens avenues for quantum material spectroscopy to investigate the structure of tunneling defects and to develop low-loss dielectrics that are urgently required for the advancement of superconducting quantum computers.
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