Anomalous charge noise in superconducting qubits

Christensen, Barbara L.; Wilen, Christopher D.; Opremcak, Alex; Nelson, J. K.; Schlenker, F.; Zimonick, C. H.; Faoro, Lara; Ioffe, L. B.; Rosen, Yaniv; Dubois, Jonathan; Plourde, B. L. T.; McDermott, Robert

doi:10.1103/physrevb.100.140503

Cited by 65 publications

(39 citation statements)

References 39 publications

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“…The QPT rates appear to be extremely slow among all the designs, making the parity switching times exceptionally long, ranging from 1 ms to up to 1.5 s. Thus, the qubits are not significantly disturbed by the QPT events during their average lifetimes. The observed QPT rates are substantially lower than those previously reported elsewhere, in which the parity switching times range between µs to ms [13,16,18,[28][29][30][31][32]. The median of Γ 1 s are at least two orders of magnitude larger than that of QPT rates suggesting that coherence of our standard devices is not currently limited by quasiparticle tunneling events.…”

contrasting

confidence: 60%

“…However, the coherence times of such qubits still need to be enhanced to meet the requirements for the error correction threshold [5,6]. One possible mechanism that can limit the qubit coherence times is the presence of non equilibrium quasiparticles [7][8][9][10][11][12][13][14][15][16][17][18][19][20], which are broken Cooper pairs out of the superconducting condensate at low temperatures. When a quasiparticle tunnels across the Josephson junction (JJ), there is a possibility of exchanging energy with the qubit, leading to depolarization.…”

mentioning

confidence: 99%

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Quasiparticle tunneling as a probe of Josephson junction quality and capacitor material in superconducting qubits

Kurter¹,

Murray

Gordon³

et al. 2021

Preprint

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Non-equilibrium quasiparticles are possible sources for decoherence in superconducting qubits because they can lead to energy decay or dephasing upon tunneling across Josephson junctions (JJs). Here, we investigate the impact of the intrinsic properties of two-dimensional transmon qubits on quasiparticle tunneling (QPT) and discuss how we can use quasiparticle dynamics to gain critical information about the quality of JJ barrier and device performance. We find the tunneling rate of the non-equilibrium quasiparticles to be sensitive to the choice of the shunting capacitor material and their geometry in qubits. In some devices, we observe an anomalous temperature dependence of the QPT rate below 100 mK that deviates from a constant background associated with non-equilibrium quasiparticles. We speculate that high transmission sites/defects within the oxide barriers of the JJs can lead to this behavior, which we can model by assuming that the defect sites have a smaller effective superconducting gap than the leads of the junction. Our results present a unique in situ characterization tool to assess the uniformity of tunnel barriers in qubit junctions and shed light on how quasiparticles can interact with various elements of the qubit circuit.

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contrasting

confidence: 60%

mentioning

confidence: 99%

Quasiparticle tunneling as a probe of Josephson junction quality and capacitor material in superconducting qubits

Kurter¹,

Murray

Gordon³

et al. 2021

Preprint

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“…We anticipate that applying this protocol to even higher level Φ;? ðωÞ (red) measured by performing SL (0, 1) , SL (1,2) transitions (j > 2) of a superconducting qubit sensor will enable one to distinguish other dephasing noise sources, such as charge noise 42 .…”

Section: Discussionmentioning

confidence: 99%

“…As an example, we measured the twofold power spectra of dephasing noise acting on the – and – transitions of a transmon, and showed that our protocol can distinguish between externally applied, known, engineered noise contributions from flux noise and photon shot noise. We anticipate that applying this protocol to even higher level transitions ( j > 2) of a superconducting qubit sensor will enable one to distinguish other dephasing noise sources, such as charge noise 42 .…”

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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“…Gate charge drift is a known weak spot of superconducting qubits with charge degrees of freedom, and it results in fluctuations of the gate charge bias point on the time scale of minutes [39]. This effect can be compensated for by implementing a suitable feedback mechanism for n G .…”

Section: Technical Aspects: Charge Qubitmentioning

confidence: 99%

Visualizing dissipative charge-carrier dynamics at the nanoscale with superconducting-charge-qubit microscopy

Jäck

2020

Phys. Rev. Research

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The investigation of novel electronic phases in low-dimensional quantum materials demands for the concurrent development of new measurement techniques that combine surface sensitivity with high spatial resolution and high measurement accuracy. We propose a quantum sensing imaging modality based on superconducting charge qubits to study dissipative charge-carrier dynamics with nanometer spatial and better than nanosecond temporal resolution. Using analytical and numerical calculations, we show that superconducting-charge-qubit microscopy (SCQM) has the potential to resolve temperature and resistivity changes in a sample as small as T 0.1 mK and ρ 1 × 10 4 cm, respectively. Among other applications, SCQM will be especially suited to study the microscopic mechanisms underlying interaction driven quantum phase transitions, to investigate the boundary modes found in novel topological insulators and, more broadly, to visualize dissipative charge-carrier dynamics occurring in mesoscopic and nanoscale devices.

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Anomalous charge noise in superconducting qubits

Cited by 65 publications

References 39 publications

Quasiparticle tunneling as a probe of Josephson junction quality and capacitor material in superconducting qubits

Quasiparticle tunneling as a probe of Josephson junction quality and capacitor material in superconducting qubits

Multi-level quantum noise spectroscopy

Visualizing dissipative charge-carrier dynamics at the nanoscale with superconducting-charge-qubit microscopy

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