Spectroscopy of a Cooper-pair box coupled to a two-level system via charge and critical current

Zaretskey, V.; Suri, Baladitya; Новиков, Сергей Петрович; Wellstood, F. C.; Palmer, B. S.

doi:10.1103/physrevb.87.174522

Cited by 17 publications

(17 citation statements)

References 37 publications

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“…Extensive prior work examining the charge offset stability of various materials showed that metallic SETs incorporating AlO x tunnel barriers demonstrate severe time instability-random, time-dependent phase fluctuations in the control curve [13][14][15][16][17][18] . These large, abrupt changes are attributed to two-level system (TLS) defects associated with amorphous AlO x , consistent with similar findings from TLS spectroscopy studies in the context of superconducting qubits [19][20][21] . In our prior work, we mitigated long-term, macroscopic resistance drift using plasma oxidized AlO x tunnel barrier devices 22 , a behavior thought to originate from the same bath of defects that causes significant charge offset drift 23,24 .…”

Section: Reduction Of Charge Offset Drift Using Plasma Oxidized Alumisupporting

confidence: 83%

Reduction of charge offset drift using plasma oxidized aluminum in SETs

Hong

Stein

Stewart

et al. 2020

Sci Rep

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Aluminum oxide ($${\text {AlO}}_x$$ AlO x )-based single-electron transistors (SETs) fabricated in ultra-high vacuum (UHV) chambers using in situ plasma oxidation show excellent stabilities over more than a week, enabling applications as tunnel barriers, capacitor dielectrics or gate insulators in close proximity to qubit devices. Historically, $${\text {AlO}}_x$$ AlO x -based SETs exhibit time instabilities due to charge defect rearrangements and defects in $${\text {AlO}}_x$$ AlO x often dominate the loss mechanisms in superconducting quantum computation. To characterize the charge offset stability of our $${\text {AlO}}_x$$ AlO x -based devices, we fabricate SETs with sub-1 e charge sensitivity and utilize charge offset drift measurements (measuring voltage shifts in the SET control curve). The charge offset drift ($$\Delta {Q_0}$$ Δ Q 0 ) measured from the plasma oxidized $${\text {AlO}}_x$$ AlO x SETs in this work is remarkably reduced (best $$\Delta {Q_0}=0.13 \, \hbox {e} \, \pm \, 0.01 \, \hbox {e}$$ Δ Q 0 = 0.13 e ± 0.01 e over $$\approx 7.6$$ ≈ 7.6 days and no observation of $$\Delta {Q_0}$$ Δ Q 0 exceeding $$1\, \hbox {e}$$ 1 e ), compared to the results of conventionally fabricated $${\text {AlO}}_x$$ AlO x tunnel barriers in previous studies (best $$\Delta {Q_0}=0.43 \, \hbox {e} \, \pm \, 0.007 \, \hbox {e}$$ Δ Q 0 = 0.43 e ± 0.007 e over $$\approx 9$$ ≈ 9 days and most $$\Delta {Q_0}\ge 1\, \hbox {e}$$ Δ Q 0 ≥ 1 e within one day). We attribute this improvement primarily to using plasma oxidation, which forms the tunnel barrier with fewer two-level system (TLS) defects, and secondarily to fabricating the devices entirely within a UHV system.

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Section: Reduction Of Charge Offset Drift Using Plasma Oxidized Alumisupporting

confidence: 83%

Reduction of charge offset drift using plasma oxidized aluminum in SETs

Hong

Stein

Stewart

et al. 2020

Sci Rep

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“…One notable experiment which found direct indication that TLS modify the critical current of a Josephson junction was reported by Zaretskey et al (2013). Here, the spectrum of a Cooper-pair box was observed to be twinned, displaying multiple parabolas shifted both in frequency and offset in gate charge.…”

Section: Tls Interactionsmentioning

confidence: 72%

Towards understanding two-level-systems in amorphous solids: insights from quantum circuits

2019

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Amorphous solids show surprisingly universal behaviour at low temperatures. The prevailing wisdom is that this can be explained by the existence of two-state defects within the material. The so-called standard tunneling model has become the established framework to explain these results, yet it still leaves the central question essentially unanswered -what are these two-level defects? This question has recently taken on a new urgency with the rise of superconducting circuits in quantum computing, circuit quantum electrodynamics, magnetometry, electrometry and metrology. Superconducting circuits made from aluminium or niobium are fundamentally limited by losses due to two-level defects within the amorphous oxide layers encasing them. On the other hand, these circuits also provide a novel and effective method for studying the very defects which limit their operation. We can now go beyond ensemble measurements and probe individual defects -observing the quantum nature of their dynamics and studying their formation, their behaviour as a function of applied field, strain, temperature and other properties. This article reviews the plethora of recent experimental results in this area and discusses the various theoretical models which have been used to describe the observations. In doing so, it summarises the current approaches to solving this fundamentally important problem in solid-state physics.

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“…As shown in equations (27) and (28), the parameters ν n and t n , n +1 contain both the Josephson coupling E J 0 and the flux . Therefore, the local perturbations and can be contributed by both the critical-current 37 and flux fluctuations.…”

Section: Resultsmentioning

confidence: 99%

Encoding a qubit with Majorana modes in superconducting circuits

You

Wang

Zhang

et al. 2014

Sci Rep

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Majorana fermions are long-sought exotic particles that are their own antiparticles. Here we propose to utilize superconducting circuits to construct two superconducting-qubit arrays where Majorana modes can occur. A so-called Majorana qubit is encoded by using the unpaired Majorana modes, which emerge at the left and right ends of the chain in the Majorana-fermion representation. We also show this Majorana qubit in the spin representation and its advantage, over a single superconducting qubit, regarding quantum coherence. Moreover, we propose to use four superconducting qubits as the smallest system to demonstrate the braiding of Majorana modes and show how the states before and after braiding Majoranas can be discriminated.

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Spectroscopy of a Cooper-pair box coupled to a two-level system via charge and critical current

Cited by 17 publications

References 37 publications

Reduction of charge offset drift using plasma oxidized aluminum in SETs

Reduction of charge offset drift using plasma oxidized aluminum in SETs

Towards understanding two-level-systems in amorphous solids: insights from quantum circuits

Encoding a qubit with Majorana modes in superconducting circuits

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