Quantum paraelectric varactors for radiofrequency measurements at millikelvin temperatures

P. Apostolidis; B. J. Villis; J. F. Chittock-Wood; J. M. Powell; A. Baumgartner; Visa Vesterinen; Slawomir Simbierowicz; Juha Hassel; M. R. Buitelaar

doi:10.1038/s41928-024-01214-z

Quantum paraelectric varactors for radiofrequency measurements at millikelvin temperatures

P. Apostolidis, B. J. Villis, J. F. Chittock-Wood, J. M. Powell, A. Baumgartner, Visa Vesterinen, Slawomir Simbierowicz, Juha Hassel, M. R. Buitelaar^*

^*Corresponding author for this work

Research output: Contribution to journal › Article › Scientific › peer-review

1 Citation (Scopus)

Abstract

Radiofrequency reflectometry can provide fast and sensitive electrical read-out of charge and spin qubits in quantum dot devices coupled to resonant circuits. In situ frequency tuning and impedance matching of the resonator circuit using voltage-tunable capacitors (varactors) is needed to optimize read-out sensitivity, but the performance of conventional semiconductor- and ferroelectric-based varactors degrades substantially in the millikelvin temperature range relevant for solid-state quantum devices. Here we show that strontium titanate and potassium tantalate, materials which can exhibit quantum paraelectric behaviour with large field-tunable permittivity at low temperatures, can be used to make varactors with perfect impedance matching and resonator frequency tuning at 6 mK. We characterize the varactors at 6 mK in terms of their capacitance tunability, dissipative losses and magnetic field insensitivity. We use the quantum paraelectric varactors to optimize the radiofrequency read-out of carbon nanotube quantum dot devices, achieving a charge sensitivity of 4.8 μe Hz^−1/2 and a capacitance sensitivity of 0.04 aF Hz^−1/2.

Original language	English
Pages (from-to)	760-767
Journal	Nature Electronics
Volume	7
Issue number	9
Early online date	5 Aug 2024
DOIs	https://doi.org/10.1038/s41928-024-01214-z
Publication status	Published - Sept 2024
MoE publication type	A1 Journal article-refereed

Funding

We thank C. Sch\u00F6nenberger for access to carbon nanotube growth facilities and P. Zubko and M. Hadjimichael for providing the SrTiO crystals and help with photolithography, respectively. We gratefully acknowledge funding from the European Research Council (ERC), Consolidator grant agreement no. 648229 (CNT-QUBIT). The VTT authors, V.V., S.S. and J.H., acknowledge support by the Research Council of Finland through grant no. 321700 and through its Centres of Excellence programme under grant nos. 336817 and 336819; in the context of the Josephson parametric amplifier, they also thank H. Pohjonen for help with lithographic masks, L. Gr\u00F6nberg for clean-room fabrication and P. Holmlund for sample preparation. A.B. is thankful for financial support by the Swiss Nanoscience Institute (SNI) and the Swiss National Science Foundation. 3

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title = "Quantum paraelectric varactors for radiofrequency measurements at millikelvin temperatures",

abstract = "Radiofrequency reflectometry can provide fast and sensitive electrical read-out of charge and spin qubits in quantum dot devices coupled to resonant circuits. In situ frequency tuning and impedance matching of the resonator circuit using voltage-tunable capacitors (varactors) is needed to optimize read-out sensitivity, but the performance of conventional semiconductor- and ferroelectric-based varactors degrades substantially in the millikelvin temperature range relevant for solid-state quantum devices. Here we show that strontium titanate and potassium tantalate, materials which can exhibit quantum paraelectric behaviour with large field-tunable permittivity at low temperatures, can be used to make varactors with perfect impedance matching and resonator frequency tuning at 6 mK. We characterize the varactors at 6 mK in terms of their capacitance tunability, dissipative losses and magnetic field insensitivity. We use the quantum paraelectric varactors to optimize the radiofrequency read-out of carbon nanotube quantum dot devices, achieving a charge sensitivity of 4.8 μe Hz−1/2 and a capacitance sensitivity of 0.04 aF Hz−1/2.",

author = "P. Apostolidis and Villis, {B. J.} and Chittock-Wood, {J. F.} and Powell, {J. M.} and A. Baumgartner and Visa Vesterinen and Slawomir Simbierowicz and Juha Hassel and Buitelaar, {M. R.}",

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AU - Baumgartner, A.

AU - Vesterinen, Visa

AU - Simbierowicz, Slawomir

AU - Hassel, Juha

AU - Buitelaar, M. R.

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N2 - Radiofrequency reflectometry can provide fast and sensitive electrical read-out of charge and spin qubits in quantum dot devices coupled to resonant circuits. In situ frequency tuning and impedance matching of the resonator circuit using voltage-tunable capacitors (varactors) is needed to optimize read-out sensitivity, but the performance of conventional semiconductor- and ferroelectric-based varactors degrades substantially in the millikelvin temperature range relevant for solid-state quantum devices. Here we show that strontium titanate and potassium tantalate, materials which can exhibit quantum paraelectric behaviour with large field-tunable permittivity at low temperatures, can be used to make varactors with perfect impedance matching and resonator frequency tuning at 6 mK. We characterize the varactors at 6 mK in terms of their capacitance tunability, dissipative losses and magnetic field insensitivity. We use the quantum paraelectric varactors to optimize the radiofrequency read-out of carbon nanotube quantum dot devices, achieving a charge sensitivity of 4.8 μe Hz−1/2 and a capacitance sensitivity of 0.04 aF Hz−1/2.

AB - Radiofrequency reflectometry can provide fast and sensitive electrical read-out of charge and spin qubits in quantum dot devices coupled to resonant circuits. In situ frequency tuning and impedance matching of the resonator circuit using voltage-tunable capacitors (varactors) is needed to optimize read-out sensitivity, but the performance of conventional semiconductor- and ferroelectric-based varactors degrades substantially in the millikelvin temperature range relevant for solid-state quantum devices. Here we show that strontium titanate and potassium tantalate, materials which can exhibit quantum paraelectric behaviour with large field-tunable permittivity at low temperatures, can be used to make varactors with perfect impedance matching and resonator frequency tuning at 6 mK. We characterize the varactors at 6 mK in terms of their capacitance tunability, dissipative losses and magnetic field insensitivity. We use the quantum paraelectric varactors to optimize the radiofrequency read-out of carbon nanotube quantum dot devices, achieving a charge sensitivity of 4.8 μe Hz−1/2 and a capacitance sensitivity of 0.04 aF Hz−1/2.

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Quantum paraelectric varactors for radiofrequency measurements at millikelvin temperatures

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