Model for<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mn>1</mml:mn><mml:mo>/</mml:mo><mml:mi>f</mml:mi></mml:math>Flux Noise in SQUIDs and Qubits

Koch, R. H.; DiVincenzo, David P.; Clarke, John

doi:10.1103/physrevlett.98.267003

Cited by 193 publications

(232 citation statements)

References 23 publications

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“…The result (12) is equivalent to the explicit subtraction of the incoherent noise S n from S k (Eqs. 6,8), with the advantage, however, of drastically reduced uncertainty, in particular at high frequencies where the (1/f -noise) signal is much smaller than the white noise. This method is appropriate for the analysis of, e.g., 1/f -type noise.…”

Section: Cross-psd: White-noise Eliminationmentioning

confidence: 99%

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Spectroscopy of low-frequency noise and its temperature dependence in a superconducting qubit

et al. 2012

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We report a direct measurement of the low-frequency noise spectrum in a superconducting flux qubit. Our method uses the noise sensitivity of a free-induction Ramsey interference experiment, comprising free evolution in the presence of noise for a fixed period of time followed by single-shot qubit-state measurement. Repeating this procedure enables Fourier-transform noise spectroscopy with access to frequencies up to the achievable repetition rate, a regime relevant to dephasing in ensemble-averaged time-domain measurements such as Ramsey interferometry. Rotating the qubit's quantization axis allows us to measure two types of noise: effective flux noise and effective criticalcurrent or charge noise. For both noise sources, we observe that the very same 1/f -type power laws measured at considerably higher frequencies (0.2 − 20 MHz) are consistent with the noise in the 0.01 − 100-Hz range measured here. We find no evidence of temperature dependence of the noises over 65 − 200 mK, and also no evidence of time-domain correlations between the two noises. These methods and results are pertinent to the dephasing of all superconducting qubits.

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Section: Cross-psd: White-noise Eliminationmentioning

confidence: 99%

“…Their noise is known to be due to local fluctuators [6][7][8][9] and the spectrum exhibits a 1/f α powerlaw dependence from hertz to tens of megahertz [10][11][12][13][14] . Its dependence on the device geometry 15,16 merits further study.…”

Section: Introductionmentioning

confidence: 99%

Spectroscopy of low-frequency noise and its temperature dependence in a superconducting qubit

et al. 2012

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“…1 In the case of qubits, this magnetic flux noise places fundamental limits on the performance and scalability of such architectures. Low frequency flux noise is widely thought to be due to fluctuations of magnetic impurities local to the superconductor wiring [2][3][4] but the identity of these impurities and the physical mechanism producing the observed fluctuations is not known. Understanding the fundamental origin of flux noise is important not only to aid in its reduction in superconducting devices, but also may provide insight into the behavior of disordered ensembles of spins at low temperature.…”

Section: Introductionmentioning

confidence: 99%

Evidence for temperature-dependent spin diffusion as a mechanism of intrinsic flux noise in SQUIDs

et al. 2014

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The intrinsic flux noise observed in superconducting quantum interference devices (SQUIDs) is thought to be due to the fluctuation of electron spin impurities, but the frequency and temperature dependence observed in experiments do not agree with the usual 1/f models. We present theoretical calculations and experimental measurements of flux noise in rf-SQUID flux qubits that show how these observations, and previous reported measurements, can be interpreted in terms of a spindiffusion constant that increases with temperature. We fit measurements of flux noise in sixteen devices, taken in the 20 − 80 mK temperature range, to the spin-diffusion model. This allowed us to extract the spin-diffusion constant and its temperature dependence, suggesting that the spin system is close to a spin-glass phase transition.

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“…Recent theoretical work has highlighted several potential sources for low frequency noise. These include ensembles of two level systems (TLS) that could be associated with dielectric defects [5,6,7], magnetic impurities in surface oxides on superconducting wiring [8] and flux noise induced by spin flips at dielectric interfaces [9]. Characterizing low frequency noise is an essential step in understanding its mechanism and in developing fabrication strategies to minimize its amplitude.…”

mentioning

confidence: 99%

Geometrical dependence of the low-frequency noise in superconducting flux qubits

et al. 2009

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A general method for directly measuring the low-frequency flux noise (below 10 Hz) in compound Josephson junction superconducting flux qubits has been used to study a series of 85 devices of varying design. The variation in flux noise across sets of qubits with identical designs was observed to be small. However, the levels of flux noise systematically varied between qubit designs with strong dependence upon qubit wiring length and wiring width. Furthermore, qubits fabricated above a superconducting ground plane yielded lower noise than qubits without such a layer. These results support the hypothesis that localized magnetic impurities in the vicinity of the qubit wiring are a key source of low frequency flux noise in superconducting devices.Qubits implemented in superconducting integrated circuits show considerable promise as building blocks of scalable quantum processors. However, low frequency noise in superconducting devices places fundamental limitations on their use in quantum information processing [1,2,3,4]. Recent theoretical work has highlighted several potential sources for low frequency noise. These include ensembles of two level systems (TLS) that could be associated with dielectric defects [5,6,7], magnetic impurities in surface oxides on superconducting wiring [8] and flux noise induced by spin flips at dielectric interfaces [9]. Characterizing low frequency noise is an essential step in understanding its mechanism and in developing fabrication strategies to minimize its amplitude. Several techniques have been exploited to indirectly measure low frequency noise in superconducting qubits [10,11]. This article describes a technique for directly measuring low frequency noise in RF-SQUID flux qubits. We present measurements performed on a series of qubits of varying wiring lengths and widths and qubits with and without superconducting shielding layers.The devices described in this paper were fabricated on an oxidized Si wafer with a Nb/Al/Al 2 O 3 /Nb trilayer process. There were two additional wiring layers, WIRA, and WIRB, above the trilayer (see Fig 1a). All wiring layers were insulated from each other with layers of sputtered SiO 2 . Eighty-five qubits with a range of geometries (wiring length, wiring width, and the presence or absence of shielding planes) were tested. Qubit wiring lengths ranged from 350 µm to 2.1 mm and wiring widths ranged from 1.4 µm to 3.5 µm. Moreover, the qubits were drawn from several wafers to control for variability in fabrication process conditions.The compound Josephson junction (CJJ) RF-SQUID is shown schematically in Fig. 1b and consists the Hamiltonian for an isolated device can be approximately expressed as [12]:where Φ q is the total flux, Q is the charge stored in the net capacitance C q across the junctions, E J = Φ 0 I q c /2π and Φ 0 = h/2e. The potential energy U (Φ q ) is monostable when β = 2πL q I c cos(πΦ cjj x /Φ 0 )/Φ 0 < 1 and classically bistable, with two counter-circulating persistent current states (denoted as |0 and |1 ) possessing persistent cur...

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Model for1/fFlux Noise in SQUIDs and Qubits

Cited by 193 publications

References 23 publications

Spectroscopy of low-frequency noise and its temperature dependence in a superconducting qubit

Spectroscopy of low-frequency noise and its temperature dependence in a superconducting qubit

Evidence for temperature-dependent spin diffusion as a mechanism of intrinsic flux noise in SQUIDs

Geometrical dependence of the low-frequency noise in superconducting flux qubits

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