Characterizing and Optimizing Qubit Coherence Based on SQUID Geometry

Braumüller, Jochen; Ding, Leon; Vepsäläinen, Antti; Sung, Youngkyu; Kjærgaard, Morten; Menke, Tim; Winik, Roni; Kim, David; Niedzielski, Bethany; Melville, Alexander; Yoder, Jonilyn; Hirjibehedin, Cyrus F.; Orlando, Terry P.; Gustavsson, Simon; Oliver, William

doi:10.1103/physrevapplied.13.054079

Cited by 67 publications

(57 citation statements)

References 38 publications

(71 reference statements)

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“…We chose the operating point (flux bias) and operating frequency range (measured spectral range) of the sensor, such that it is dominantly affected by the engineered noise. However, the technique discussed here can be also applied to measure intrinsic noise of transmons such as 1/ f flux noise 3 , 44 , 45 . Notably, by biasing the sensor at more flux-sensitive point, the sensitivity to flux noise can be further increased in order to detect intrinsic flux noise.…”

Section: Discussionmentioning

confidence: 99%

Multi-level quantum noise spectroscopy

et al. 2021

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System noise identification is crucial to the engineering of robust quantum systems. Although existing quantum noise spectroscopy (QNS) protocols measure an aggregate amount of noise affecting a quantum system, they generally cannot distinguish between the underlying processes that contribute to it. Here, we propose and experimentally validate a spin-locking-based QNS protocol that exploits the multi-level energy structure of a superconducting qubit to achieve two notable advances. First, our protocol extends the spectral range of weakly anharmonic qubit spectrometers beyond the present limitations set by their lack of strong anharmonicity. Second, the additional information gained from probing the higher-excited levels enables us to identify and distinguish contributions from different underlying noise mechanisms.

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Section: Discussionmentioning

confidence: 99%

Multi-level quantum noise spectroscopy

et al. 2021

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“…However, they also independently tackle other aspects of the discussed effect. In details, the model of Koch et al 20 is supported by the recent experimental studies that consider qubit coherence optimization based on SQUID geometry 26 . Some other models emphasize the interactions between surface spins 21 – 24 , in agreement with the experimental observations provided in 27 .…”

Section: Introductionmentioning

confidence: 89%

Magnetic flux noise in superconducting qubits and the gap states continuum

Szczęśniak

Kais

2021

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In the present study we investigate the selected local aspects of the metal-induced gap states (MIGSs) at the disordered metal–insulator interface, that were previously proposed to produce magnetic moments responsible for the magnetic flux noise in some of the superconducting qubit modalities. Our analysis attempts to supplement the available studies and provide new theoretical contribution toward their validation. In particular, we explicitly discuss the behavior of the MIGSs in the momentum space as a function of the onsite energy deviation, that mimics random potential disorder at the interface in the local approximation. It is found, that when the difference between the characteristic electronic potentials in the insulator increases, the corresponding MIGSs become more localized. This effect is associated with the increasing degree of the potential disorder that was earlier observed to produce highly localized MIGSs in the superconducting qubits. At the same time, the presented findings show that the disorder-induced localization of the MIGSs can be related directly to the decay characteristics of these states as well as to the bulk electronic properties of the insulator. As a result, our study reinforces plausibility of the previous corresponding investigations on the origin of the flux noise, but also allows to draw future directions toward their better verification.

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“…(b) The energy level model of two-level defects. The energy level difference depends on the local barrier height difference and the coupling strength 磁场较强的SQUID环路附近, 如图5(b)所示, 磁通比特的磁通噪声幅度正比环路的周长 [72] . [21,74] .…”

Section: 磁性杂质mentioning

confidence: 99%

“…(a) 超导量子比特芯片中磁性杂质的分布和原子结构示意图. (b) 磁通量子比特的磁通噪声和其超导环路周长成正比[72] . Reprinted with permission, Copyright (2020) by the American Physical Society Figure5Magnetic impurities.…”

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confidence: 99%