Radio-frequency amplifiers based on dc SQUIDs

Mück, Michael; McDermott, Robert

doi:10.1088/0953-2048/23/9/093001

Cited by 48 publications

(36 citation statements)

References 50 publications

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“…(7). The imprecision is approximately as expected given the noise of the cryogenic amplifier (see supplementary material), and could therefore be improved by using an improved superconducting amplifier 42 . Alternatively, the conversion of displacement to current could be improved with larger DC gate voltage, while increasing the quality factor of the tank circuit could give larger transimpedance.…”

supporting

confidence: 53%

Measuring carbon nanotube vibrations using a single-electron transistor as a fast linear amplifier

Wen

Ares

Pei

et al. 2018

Applied Physics Letters

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We demonstrate sensitive and fast electrical measurements of a carbon nanotube mechanical resonator. The nanotube is configured as a single-electron transistor, whose conductance is a sensitive transducer for its own displacement. Using an impedance-matching circuit followed by a cryogenic amplifier, the vibrations can be monitored at radio frequency. The sensitivity of this continuous displacement measurement approaches within a factor 470 of the standard quantum limit.Suspended carbon nanotubes are mechanical resonators 1 with low mass, high compliance, and high quality factor 2,3 , which makes them sensitive electromechanical detectors for tiny forces 4 and masses 5-7 . The timeaveraged current through a vibrating nanotube probes electron-phonon coupling 8-11 , non-linear dissipation 12 , and mechanical mode mixing 13 on the nanoscale. Timeresolved measurements go further, allowing for the study of transient effects such as spin switching 14,15 , mechanical dephasing 16 , or even force-detected magnetic resonance 17 . Although the low mass favors large electromechanical coupling, the large electrical impedance of nanotube devices makes it difficult to amplify the current signal with high sensitivity and bandwidth, especially since low temperatures are needed to suppress thermal noise.One approach is to downconvert the electromechanical signal to a frequency within the bandwidth of a cryogenic current amplifier, using either two-source mixing or the non-linear conductance of the nanotube itself 18,19 . For fast measurements, parasitic capacitance must be minimised by placing the amplifier close to the resonator. The resulting heat load has usually prevented operation below 1 K 16,19 , although recently such a setup achieved high sensitivity at millikelvin temperatures and with a bandwidth of 87 kHz 20 . A second approach, with higher bandwidth, is to detect the changing capacitance between the vibrating nanotube and a pickup antenna 21 . However, the small size of the pickup antenna means that a large electric field is needed to generate an appreciable signal. A third approach, used for other kinds of nanoscale resonator 22,23 , is to connect the resonator's output directly to a fast amplifier matched to the cable impedance (typically 50 Ω). However, the electrical divider formed between the large impedance of the device and the small impedance of the cable degrades the signal.Here, we demonstrate a circuit that combines sensitivity with high speed by monitoring the electromechanical signal directly, while requiring only a DC bias voltage. The circuit exploits a single-electron transistor (SET) dea) Electronic mail: e.a.laird@lancaster.ac.uk fined within the nanotube as the initial stage of displacement amplification 2,[9][10][11][24][25][26][27] . The SET output current, which depends linearly on displacement, is monitored directly at radio frequency using a low-noise cryogenic radio-frequency (RF) amplifier with MHz bandwidth. To improve the coupling between the SET and the cryogenic amplifier, we use an impe...

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supporting

confidence: 53%

Measuring carbon nanotube vibrations using a single-electron transistor as a fast linear amplifier

Wen

Ares

Pei

et al. 2018

Applied Physics Letters

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“…In this section we use graphs to analyze a complicated multi-mode system, the dc-SQUID amplifier. dc-SQUIDs are a type of superconducting amplifier with noise temperatures approaching the standard quantum limit [31][32][33]. Since dc-SQUIDs also have inherently low power dissipation (in addition to high gain and directionality [34]), they have been the subject of several applied superconductivity efforts to produce reliable amplifiers for microwave quantum information measurements.…”

Section: Directionality Of Dc-squid Amplifiersmentioning

confidence: 99%

Graph-based analysis of nonreciprocity in coupled-mode systems

2015

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In this work we derive the general conditions for obtaining nonreciprocity in multi-mode parametrically-coupled systems. The results can be applied to a broad variety of optical, microwave, and hybrid systems including recent electro-and opto-mechanical devices. In deriving these results, we use a graph-based methodology to derive the scattering matrix. This approach naturally expresses the terms in the scattering coefficients as separate graphs corresponding to distinct coupling paths between modes such that it is evident that nonreciprocity arises as a consequence of multi-path interference and dissipation in key ancillary modes. These concepts facilitate the construction of new devices in which several other characteristics might also be simultaneously optimized. As an example, we synthesize a novel three-mode unilateral amplifier design by use of graphs. Finally, we analyze the isolation generated in a common parametric multi-mode system, the dc-SQUID.

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“…By taking the square and then summing Eqs. (21) and (22) one gets the algebraic equation for the amplitude only,…”

Section: Equations Of Motionmentioning

confidence: 99%

Multistability of a Josephson parametric amplifier coupled to a mechanical resonator

2014

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We study the dynamics of a Josephson parametric amplifier (JPA) coupled to a mechanical oscillator, as realized with a dc superconducting quantum interference device (SQUID) with an embedded movable arm. We analyze this system in the regime when the frequency of the mechanical oscillator is comparable in magnitude to the plasma oscillation of the SQUID. When the nanomechanical resonator is driven, it strongly affects the dynamics of the JPA. We show that this coupling can considerably modify the dynamics of the JPA and induce its multistability rather than common bistability. This analysis is relevant if one considers a JPA for detection of mechanical motion.

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Radio-frequency amplifiers based on dc SQUIDs

Cited by 48 publications

References 50 publications

Measuring carbon nanotube vibrations using a single-electron transistor as a fast linear amplifier

Measuring carbon nanotube vibrations using a single-electron transistor as a fast linear amplifier

Graph-based analysis of nonreciprocity in coupled-mode systems

Multistability of a Josephson parametric amplifier coupled to a mechanical resonator

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