Evolution of1/fFlux Noise in Superconducting Qubits with Weak Magnetic Fields,Physical Review Letters

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Evolution of1/fFlux Noise in Superconducting Qubits with Weak Magnetic Fields
Physical Review Letters ( IF 8.1 ) Pub Date : 2023-05-31 , DOI: 10.1103/physrevlett.130.220602
David A Rower _{1,

2} , Lamia Ateshian _{2,

3} , Lauren H Li ₁ , Max Hays ₂ , Dolev Bluvstein ₄ , Leon Ding _{1,

2} , Bharath Kannan _{2,

3} , Aziza Almanakly _{2,

3} , Jochen Braumüller ₂ , David K Kim ₅ , Alexander Melville ₅ , Bethany M Niedzielski ₅ , Mollie E Schwartz ₅ , Jonilyn L Yoder ₅ , Terry P Orlando _{2,

3} , Joel I-Jan Wang ₂ , Simon Gustavsson ₂ , Jeffrey A Grover ₂ , Kyle Serniak _{2,

5} , Riccardo Comin ₁ , William D Oliver _{1,

2,

3,

5}

Affiliation

The microscopic description of

1 / f

magnetic flux noise in superconducting circuits has remained an open question for several decades despite extensive experimental and theoretical investigation. Recent progress in superconducting devices for quantum information has highlighted the need to mitigate sources of qubit decoherence, driving a renewed interest in understanding the underlying noise mechanism(s). Though a consensus has emerged attributing flux noise to surface spins, their identity and interaction mechanisms remain unclear, prompting further study. Here, we apply weak in-plane magnetic fields to a capacitively shunted flux qubit (where the Zeeman splitting of surface spins lies below the device temperature) and study the flux-noise-limited qubit dephasing, revealing previously unexplored trends that may shed light on the dynamics behind the emergent

1 / f

noise. Notably, we observe an enhancement (suppression) of the spin-echo (Ramsey) pure-dephasing time in fields up to

B = 100 G

. With direct noise spectroscopy, we further observe a transition from a

1 / f

to approximately Lorentzian frequency dependence below 10 Hz and a reduction of the noise above 1 MHz with increasing magnetic field. We suggest that these trends are qualitatively consistent with an increase of spin cluster sizes with magnetic field. These results should help to inform a complete microscopic theory of

1 / f

flux noise in superconducting circuits.

中文翻译：

弱磁场超导量子比特中 1/fFlux 噪声的演化

的微观描述

1个 / F

尽管进行了广泛的实验和理论研究，但超导电路中的磁通量噪声几十年来一直是一个悬而未决的问题。用于量子信息的超导器件的最新进展凸显了减轻量子比特退相干源的必要性，从而激发了人们对理解潜在噪声机制的新兴趣。尽管已经出现将通量噪声归因于表面自旋的共识，但它们的身份和相互作用机制仍不清楚，这促使进一步研究。在这里，我们将弱平面内磁场应用于电容分流通量量子位（其中表面自旋的塞曼分裂位于器件温度以下）并研究通量噪声限制的量子位相移，揭示了以前未探索的趋势，这些趋势可能会阐明涌现背后的动力