Circuit quantum electrodynamics of granular aluminum resonators

Maleeva, N.; Grünhaupt, Lukas; Klein, Thierry; Lévy-Bertrand, F.; Dupré, Olivier; Calvo, M.; Valenti, Francesco; Winkel, Patrick; Friedrich, F.; Wernsdorfer, Wolfgang; Ustinov, A. V.; Rotzinger, Hannes; Monfardini, A.; Fistul, M. V.; Pop, I.

doi:10.1038/s41467-018-06386-9

Cited by 127 publications

(136 citation statements)

References 41 publications

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“…, here P in is estimated from the output power of the vector network analyzer by taking into account the total attenuation in the cryostat (see Supplemental Material [54]). For resonator A, Q i shows an increase by a factor of 4 between n ¼ 1 and 100, reaching 6 × 10 5 before the resonator bifurcates due to its intrinsic nonlinearity [63]. Seven times larger in cross section, resonator B shows a smaller increase From FEM simulations we expect the kinetic inductance to be three orders of magnitude larger than the geometric inductance.…”

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confidence: 92%

Loss Mechanisms and Quasiparticle Dynamics in Superconducting Microwave Resonators Made of Thin-Film Granular Aluminum

et al. 2018

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Superconducting high kinetic inductance elements constitute a valuable resource for quantum circuit design and millimeter-wave detection. Granular aluminum (grAl) in the superconducting regime is a particularly interesting material since it has already shown a kinetic inductance in the range of nH/□ and its deposition is compatible with conventional Al/AlOx/Al Josephson junction fabrication. We characterize microwave resonators fabricated from grAl with a room temperature resistivity of 4×10^{3} μΩ cm, which is a factor of 3 below the superconductor to insulator transition, showing a kinetic inductance fraction close to unity. The measured internal quality factors are on the order of Q_{i}=10^{5} in the single photon regime, and we demonstrate that nonequilibrium quasiparticles (QPs) constitute the dominant loss mechanism. We extract QP relaxation times in the range of 1 s and we observe QP bursts every ∼20 s. The current level of coherence of grAl resonators makes them attractive for integration in quantum devices, while it also evidences the need to reduce the density of nonequilibrium QPs.

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confidence: 92%

Loss Mechanisms and Quasiparticle Dynamics in Superconducting Microwave Resonators Made of Thin-Film Granular Aluminum

et al. 2018

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“…It can therefore be tuned over a wide range, reaching values up to ∼ nH/ , while maintaining internal quality factors on the order of 10 5 in the single photon regime [51][52][53]. Moreover, the Kerr non-linearity can be reduced by orders of magnitude [54] compared to superinductors made of mesoscopic Josephson junction arrays [55], which helps to suppress the unwanted coupling between the qubit and the environment. Figure 1a) shows the equivalent circuit of the fluxonium qubit coupled to the readout resonator.…”

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confidence: 99%

Granular aluminium as a superconducting material for high-impedance quantum circuits

et al. 2019

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Superconducting quantum information processing machines are predominantly based on microwave circuits with relatively low characteristic impedance, of about 100 Ohm, and small anharmonicity, which can limit their coherence and logic gate fidelity. A promising alternative are circuits based on so-called superinductors, with characteristic impedances exceeding the resistance quantum RQ = 6.4 kΩ. However, previous implementations of superinductors, consisting of mesoscopic Josephson junction arrays, can introduce unintended nonlinearity or parasitic resonant modes in the qubit vicinity, degrading its coherence. Here we present a fluxonium qubit design using a granular aluminum (grAl) superinductor strip. Granular aluminum is a particularly attractive material, as it self-assembles into an effective junction array with a remarkably high kinetic inductance, and its fabrication can be in-situ integrated with standard aluminum circuit processing. The measured qubit coherence time T R 2 up to 30 µs illustrates the potential of grAl for applications ranging from protected qubit designs to quantum limited amplifiers and detectors. arXiv:1809.10646v1 [cond-mat.supr-con]

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“…Because reduced K eff is important to improve dynamical range, several methods have been introduced to reduce non-linearity in parametric amplifiers. One first option is to use the intrinsic non-linearity of superconductors such as Niobium [28], NbN [29] or granular Aluminium [30], since they often come with very weak nonlinearities spanning from 20 mHz to 30 kHz for resonators in the GHz range. However, these non-linearities are so weak that extremely large pump powers are required resulting in experimental challenges.…”

Section: Decreasing Non-linearity Using Arraysmentioning

confidence: 99%

Understanding the Saturation Power of Josephson Parametric Amplifiers Made from SQUID Arrays

et al. 2019

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We report on the implementation and detailed modelling of a Josephson Parametric Amplifier (JPA) made from an array of eighty Superconducting QUantum Interference Devices (SQUIDs), forming a non-linear quarter-wave resonator. This device was fabricated using a very simple single step fabrication process. It shows a large bandwidth (45 MHz), an operating frequency tunable between 5.9 GHz and 6.8 GHz and a large input saturation power (−117 dBm) when biased to obtain 20 dB of gain. Despite the length of the SQUID array being comparable to the wavelength, we present a model based on an effective non-linear LC series resonator that quantitatively describes these figures of merit without fitting parameters. Our work illustrates the advantage of using arraybased JPA since a single-SQUID device showing the same bandwidth and resonant frequency would display a saturation power 15 dB lower.

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Circuit quantum electrodynamics of granular aluminum resonators

Cited by 127 publications

References 41 publications

Loss Mechanisms and Quasiparticle Dynamics in Superconducting Microwave Resonators Made of Thin-Film Granular Aluminum

Loss Mechanisms and Quasiparticle Dynamics in Superconducting Microwave Resonators Made of Thin-Film Granular Aluminum

Granular aluminium as a superconducting material for high-impedance quantum circuits

Understanding the Saturation Power of Josephson Parametric Amplifiers Made from SQUID Arrays

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