Carbon nanotube single-electron devices at audio and radio frequencies

A single-electron transistor is the most sensitive charge detector known today. It is formed by a small piece of a conductor coupled to electrodes by tunnel junctions. At low frequencies, the charge sensitivity is limited by the 1/f-noise. The use of a radio-frequency modulation technique allows a wide operational bandwidth with negligible 1/f-noise contribution. In this Thesis, a multiwalled carbon nanotube brought to contact with metal electrodes was demonstrated to work as a single-electron transistor. A scanning probe manipulation scheme was developed and it was used to fabricate the sample. The manipulation scheme was also employed to construct more complicated electronic carbon nanotube devices. It was shown that it is possible to construct a multiwalled carbon nanotube single-electron transistor having an equal to, or even higher charge sensitivity than a typical metallic device. The transmission-line parameters of the multiwalled carbon nanotube were estimated by using the environment-quantum-fluctuation theory. The radio-frequency single-electron transistor setup was analyzed in depth and a simplified engineering formula for the charge sensitivity was derived. A radio-frequency single-electron transistor setup using a multiwalled carbon nanotube single-electron transistor was demonstrated in the built cryogenic high-frequency measurement system. A low-temperature high-electron-mobility-transistor amplifier was designed and built for the system. Measurements of the amplifier indicated a noise temperature of three Kelvins.reviewe

Cyclostationary measurement of low-frequency odd moments of current fluctuations

Measurement of odd moments of current fluctuations is difficult due to strict requirements for band-pass filtering. We propose how these requirements can be overcome using cyclostationary driving of the measured signal and indicate how the measurement accuracy can be tested through the phase dependence of the moments of the fluctuations. We consider two schemes, the mixing scheme and the statistics scheme, where the current statistics can be accessed. We also address the limitations of the schemes, due to excess noise and due to the effects of the environment, and, finally, discuss the required measurement times for typical setups.Comment: 13 pages, 3 figure

Band Engineering in Cooper-Pair Box: Dispersive Measurements of Charge and Phase

Low-frequency susceptibility of the split Cooper-pair box (SCPB) is investigated for use in sensitive measurements of external phase or charge. Depending on the coupling scheme, the box appears as either inductive or capacitive reactance which depends on external phase and charge. While coupling to the source-drain phase, we review how the SCPB looks like a tunable inductance, which property we used to build a novel radio-frequency electrometer. In the dual mode of operation, that is, while observed at the gate input, the SCPB looks like a capacitance. We concentrate on discussing the latter scheme, and we show how to do studies of fast phase fluctuations at a sensitivity of 1 mrad/$\sqrt{Hz}$ by measuring the input capacitance of the box.Comment: LT24 invited paper, 4 page

Quantum capacitive phase detector

We discuss how a single Cooper-pair transistor may be used to detect the superconducting phase difference by using the phase dependence of the input capacitance from gate to the ground. The proposed device has a low power dissipation because its operation is in principle free from quasiparticle generation. According to the sensitivity estimates the device may be used for efficient qubit readout in a galvanically isolated and symmetrized circuit.Comment: 5 pages, published for

PyNomo software dataset for sciences and engineering nomogram construction

This article examines different python-based codes to be run under PyNomo nomographer software to represent alignment charts or nomograms for formulas commonly used in sciences and engineering studies. PyNomo nomographer supports nine basic types of nomograms based on the format of the mathematical equation. The examined PyNomo codes cover the construction of the following types of nomogram: type 1, type 2, type 7, type 8, type 9, and type 10. Each PyNomo script includes some background and the underlying mathematics for the nomogram construction and how to implement each code into PyNomo software. Potential users can use these PyNomo codes, as template scripts, to customize and construct their own nomograms for a variety of technical applications. That is especially true since a considerable number of science and engineering equations fall into one of these covered nomogram types depending on the equation form involved.This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Please declare any financial interests/personal relationships which may be considered as potential competing interests here

Nomography: A renewed pedagogical tool to sciences and engineering high-education studies

Nomography is defined as a branch of mathematics in which methods of graphical representation of functional dependencies are studied. The resulting graphs are called nomograms, alignment charts, or abacs. Along the past century, this science branch experienced extensive development and use in many contexts to support scientists and engineers with accurate and fast calculations of complex formulas to a practical precision. However, nomography declined by the end of the twentieth century with the development and popularisation of more capable and powerful personal computers and handheld calculators. Despite this context, nomography remains attractive due to its potential for rapid and accurate graphical calculations contributing to a better understanding of complex formulas. Thus, this work defines the alignment charts and their capabilities to justify their importance as graphical tools in sciences and engineering studies. Also, PyNomo software is introduced to build vector-based and scalable nomograms. Then, this work emphasizes the importance of including nomography as a valuable and renewed computational tool, in conjunction with PyNomo software, in an academic context. In line with that, several nomograms, which have been obtained with PyNomo software, are examined to grasp the true importance of this science branch and its capabilities in an educational context.The authors would like to thank Dr John Douglas and the other anonymous reviewer for their helpful comments on aspects of this study which were useful in revising this article

Design of cryogenic 700 MHz HEMT amplifier

We present a way to design a high-frequency low-temperature pHEMT-based balanced amplifier. The design is based on measured cryogenic S-parameters combined with a small-signal noise model. Using the design process we constructed an amplifier that was measured to have a gain of 16 dB and a noise temperature of ∼3 K when cooled to 4.2 K.Non Peer reviewe