Low-temperature<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mn>1</mml:mn><mml:mo>/</mml:mo><mml:mi>f</mml:mi></mml:mrow></mml:math>noise in microwave dielectric constant of amorphous dielectrics in Josephson qubits

Burin, Alexander L.; Matityahu, Shlomi; Schechter, Moshe

doi:10.1103/physrevb.92.174201

Cited by 32 publications

(52 citation statements)

References 39 publications

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“…The electron-TLS interaction analyzed here provides a mechanism of decoherence and fluctuations that may be relevant, e.g., for semiconductor devices such as gated quantum dots and field-effect transistors. Likewise, it can explain a reduction in mutual TLS coupling due to enhanced TLS relaxation rates as it was found in recent experiments where a superconducting resonator was capped by a normal conducting platinum layer [26,27].…”

Section: Iv: Summarysupporting

confidence: 53%

Electronic decoherence of two-level systems in a Josephson junction

et al. 2017

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The sensitivity of superconducting qubits allows for spectroscopy and coherence measurements on individual two-level systems present in the disordered tunnel barrier of an Al/AlOx/Al Josephson junction. We report experimental evidence for the decoherence of two-level systems by Bogoliubov quasiparticles leaking into the insulating AlOx barrier. We control the density of quasiparticles in the junction electrodes either by the sample temperature or by injecting them using an on-chip dc-SQUID driven to its resistive state. The decoherence rates were measured by observing the two-level system's quantum state evolving under application of resonant microwave pulses and were found to increase linearly with quasiparticle density, in agreement with theory. This interaction with electronic states provides a noise and decoherence mechanism that is relevant for various microfabricated devices such as qubits, single-electron transistors, and field-effect transistors. The presented experiments also offer a possibility to determine the location of the probed two-level systems across the tunnel barrier, providing clues about the fabrication step in which they emerge. I: INTRODUCTIONWhile superconducting circuits based on Josephson junctions (JJs) rapidly mature towards favorable and applicable qubits for quantum computers [1-3], a major source of their decoherence traces back to spurious material defects that give rise to the formation of low-energy two-level systems (TLSs). On the other hand, sensitivity to tiny perturbations turns JJ qubits into ideal tools to study the properties of TLSs. For example, microwave spectroscopy of JJ phase qubits shows avoided level crossings revealing the TLSs' quantum character as well as their coherent interaction with the qubit [4]. Various microscopic models including dangling bonds, Andreev bound states [5], and Kondo fluctuators [6] have been suggested to explain the origin of TLSs. There is growing evidence [7,8], however, that they are formed by small groups of atoms that are able to tunnel between two energetically almost equivalent configurations. This is most strongly supported by recent experiments where the TLSs' energy splittings were tuned by applying external static strain [9]. TLSs are the source of lowenergy excitations, which are also responsible for the thermal, acoustic, and dielectric properties of glasses at temperatures below 1 K [10,11], which are well studied in bulk materials. Inherent to disordered solids, they are present in surface oxides and insulating layers of any microfabricated device as well as in the tunnel barriers of Josephson junctions.In contrast to traditional measurements performed on glasses that probe huge ensembles of TLSs, the sensitivity of JJ-based qubits allows one to address single TLSs and determine their individual properties. Strain-tuning experiments, e.g., measure a TLS's deformation potential [9] and allow for a detailed analysis of the coherent interaction between two TLSs brought into resonance [12]. In another experiment, the temperatu...

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Section: Iv: Summarysupporting

confidence: 53%

Electronic decoherence of two-level systems in a Josephson junction

et al. 2017

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“…The TLS relaxation and decoherence times originated from the TLS interaction with phonons are defined as [14,20,31,32] 1…”

Section: Rate Equation Formalism and Tls Loss Tangentmentioning

confidence: 99%

“…Both the microwave absorption and the noise induced by TLSs are dramatically sensitive to their interactions [10,[13][14][15][16][17][18]. While the 1/f noise is reasonably interpreted within the interacting TLS model [13,14], the problem of non-linear microwave absorption is not resolved yet, in spite of the numerous efforts [16,17,19]. Here we propose a solution to this long-standing problem integrating the earlier developed rate equation model for TLS density matrix time evolution [20,21] briefly introduced in Sec.…”

Section: Introductionmentioning

confidence: 99%

Theory of nonlinear microwave absorption by interacting two-level systems

Burin

Maksymov

2018

Phys. Rev. B

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The microwave absorption and noise caused by quantum two-level systems (TLS) dramatically suppress the coherence in Josephson junction qubits that are promising candidates for quantum information applications. It is a challenge to understand microwave absorption by TLSs because of the spectral diffusion resulting from fluctuations in their resonant frequencies induced by their long-range interactions. Here we treat the spectral diffusion explicitly using the generalized master equation formalism. The proposed theory predicts that the linear absorption regime holds while a TLS Rabi frequency is smaller than their phase decoherence rate. At higher external fields, a novel non-linear absorption regime is found with the loss tangent inversely proportional to the intensity of the field. The theory can be generalized to acoustic absorption and lower dimensions realized in superconducting qubits.

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“…18,23 Recently, two theories have incorporated TLS-TLS interactions in the form of spectral diffusion to explain the anomalous scaling. 24,25 In order to test these predictions for our system, we use a homodyne detection setup depicted in Fig. 1(a).…”

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confidence: 99%

Transmission-line resonators for the study of individual two-level tunneling systems

Brehm

Bilmes

Weiß

et al. 2017

Applied Physics Letters

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Parasitic two-level tunneling systems (TLS) emerge in amorphous dielectrics and constitute a serious nuisance for various microfabricated devices, where they act as a source of noise and decoherence. Here, we demonstrate a new test bed for the study of TLS in various materials which provides access to properties of individual TLS as well as their ensemble response. We terminate a superconducting transmission-line resonator with a capacitor that hosts TLS in its dielectric. By tuning TLS via applied mechanical strain, we observe the signatures of individual TLS strongly coupled to the resonator in its transmission characteristics and extract the coupling components of their dipole moments and energy relaxation rates. The strong and well-defined coupling to the TLS bath results in pronounced resonator frequency fluctuations and excess phase noise, through which we can study TLS ensemble effects such as spectral diffusion, and probe theoretical models of TLS interaction.

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Low-temperature1/fnoise in microwave dielectric constant of amorphous dielectrics in Josephson qubits

Cited by 32 publications

References 39 publications

Electronic decoherence of two-level systems in a Josephson junction

Electronic decoherence of two-level systems in a Josephson junction

Theory of nonlinear microwave absorption by interacting two-level systems

Transmission-line resonators for the study of individual two-level tunneling systems

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