Circuit models and SPICE macro-models for quantum Hall effect devices

Quantum Hall effect (QHE) devices are a pillar of modern quantum electrical metrology. Electrical networks including one or more QHE elements can be used as quantum resistance and impedance standards. The analysis of these networks allows metrologists to evaluate the effect of the inevitable parasitic parameters on their performance as standards. This paper presents a systematic analysis of the various circuit models for QHE elements proposed in the literature, and the development of a new model. This last model is particularly suited to be employed with the analogue electronic circuit simulator SPICE. The SPICE macro-model and examples of SPICE simulations, validated by comparison with the corresponding analytical solution and/or experimental data, are provided

A correlation noise spectrometer for flicker noise measurement in graphene samples

We present a high-resolution digital correlation spectrum analyzer for the measurement of low frequency resistance fluctuations in graphene samples. The system exploits the cross-correlation method to reject the amplifiers' noise. The graphene sample is excited with a low-noise DC current. The output voltage is fed to two two-stage low-noise amplifiers connected in parallel; the DC signal component is filtered by a high-pass filter with a cutoff frequency of 34 mHz. The amplified signals are digitized by a two-channel synchronous ADC board; the cross-periodogram, which rejects uncorrelated amplifiers' noise components, is computed in real time. As a practical example, we measured the noise cross-spectrum of graphene samples in the frequency range from 0.153 Hz to 10 kHz, both in two- and four-wire configurations, and for different bias currents. We report here the measurement setup, the data analysis and the error sources

A three-arm current comparator bridge, for impedance comparisons over the complex plane

We present here the concept of three-arm current comparator impedance bridge, which allows comparisons among three unlike impedances. Its purpose is the calibration of impedances having arbitrary phase angles, against calibrated nearly-pure impedances. An analysis of the bridge optimal setting and proper operation is presented. To test the concept, a two terminal-pair digitally-assisted bridge has been realized; measurements of an air-core inductor and of an RC network versus decade resistance and capacitance standards, at kHz frequency, have been performed. The bridge measurements are compatible with previous knowledge of the standards' values with relative deviations in the 10^-5 -- 10^-6 range

Applications in Quantum Hypothesis Testing

L'abstract è presente nell'allegato / the abstract is in the attachmen

Effects of Economic and Environmental Reform on the Diffusion of Cleaner Coal Technology in China

Coal is both the major fuel for China\u27s economic development and the major source of its severe air pollution. China\u27s reliance on coal for nearly three-quarters of its primary energy has contributed to local air pollution, regional acid rain and global climate change. At the same time, the country\u27s coal consumption has electrified its growing cities and helped Chinese steel and chemical industries to become international powerhouses. This contribution considers how the intertwined issues of environmental reform and economic reform have affected efforts to reduce coal-related air pollution in China. Our analysis focuses on government efforts to promote the diffusion of cleaner coal technologies (CCTs) among industrial state-owned enterprises (SOEs). We utilize a framework of \u27fragmented authoritarianism\u27 (Lieberthal and Oksenberg, 1988) for our investigation of CCT-related policies, examining the changing relationships among central and local government actors and enterprises during the past decade of economic reforms. We also examine how economic reforms have influenced environmental policy development at the centre, environmental policy implementation at the local level, and the response of enterprises to these changing policies. Fragmented authoritarianism helps explain why, despite government efforts to promote technologies that reduce coal-related air pollution in China, the diffusion of CCT has been slow