200 research outputs found
Theoretical aspects of Microwave Frequency Transport in Generic Dimensionality Semiconductors
The present work can be classified as an investigation for the theoretical study of semiconductors in the microwave (?w) frequency domain. This range owns two properties that let it to be a hot subject for the next years: from one side, there is a basic need of such a characterization to get a satisfactory description of the fundamental solid state physics; from the other side there is the urgent need to analyze and increase performances of technological products in order to improve the quality of services in human life and business. IBM announced in March 2002 the realization of the fastest silicon-based transistor, by using a modified design of a heterojunction bipolar transistor (HBT) and SiGe technology, working at a speed of 210 GHz. New methods to allow contactless measurements techniques of the transport properties of semiconductors are needed for a ?w characterization to cover the whole range
Coherent Transport of Quantum States by Deep Reinforcement Learning
Some problems in physics can be handled only after a suitable \textit{ansatz
}solution has been guessed. Such method is therefore resilient to
generalization, resulting of limited scope. The coherent transport by adiabatic
passage of a quantum state through an array of semiconductor quantum dots
provides a par excellence example of such approach, where it is necessary to
introduce its so called counter-intuitive control gate ansatz pulse sequence.
Instead, deep reinforcement learning technique has proven to be able to solve
very complex sequential decision-making problems involving competition between
short-term and long-term rewards, despite a lack of prior knowledge. We show
that in the above problem deep reinforcement learning discovers control
sequences outperforming the \textit{ansatz} counter-intuitive sequence. Even
more interesting, it discovers novel strategies when realistic disturbances
affect the ideal system, with better speed and fidelity when energy detuning
between the ground states of quantum dots or dephasing are added to the master
equation, also mitigating the effects of losses. This method enables online
update of realistic systems as the policy convergence is boosted by exploiting
the prior knowledge when available. Deep reinforcement learning proves
effective to control dynamics of quantum states, and more generally it applies
whenever an ansatz solution is unknown or insufficient to effectively treat the
problem.Comment: 5 figure
Narrow filtered DPSK implements order-1 CAPS optical line coding
A novel family of optical line codes has been presented elsewhere, here referred to as combined amplitude-phase shift (CAPS) codes. We show here that narrow filtering of a differential phase shift keying signal with bandwidth equal to about 2/3 of the bit rate turns out to closely implement the order-1 CAPS line coding. Performance of the two systems is compared for various types of optical filters
Measuring the Temperature of a Mesoscopic Quantum Electron System by means of Single Electron Statistics
We measure the temperature of a mesoscopic system consisting of an
ultra-dilute two dimensional electron gas at the interface in a
metal-oxide-semiconductor field effect transistor (MOSFET) quantum dot by means
of the capture and emission of an electron in a point defect close to the
interface. Contrarily to previous reports, we show that the capture and
emission by point defects in Si n-MOSFETs can be temperature dependent down to
800 mK. As the finite quantum grand canonical ensemble model applies, the time
domain charge fluctuation in the defect is used to determine the temperature of
the few electron gas in the channel.Comment: 4 Figures (color
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