The influence of interactions on electronic transport properties can be observed in many nanostructures, in particular in a so-called quantum dot, namely a spatially isolated island in and out of which electrons can tunnel. Due to its small size, the quantum dot supports discretely-spaced energy levels; considering only one of these levels for simplicity, we model the dot with the Hamiltonian H...

The capacitive couplings between gate-defined quantum dots and their gates vary considerably as a function of applied gate voltages. The conversion between gate voltages and the relevant energy scales is usually performed in a regime of rather symmetric dot-lead tunnel couplings strong enough to allow direct transport measurements. Unfortunately, this standard procedure fails for weak and possi...

The energy levels of CdSe quantum dots are studied by scanning tunneling spectroscopy. By varying the tip−dot distance, we switch from “shell-filling” spectroscopy (where electrons accumulate in the dot and experience mutual repulsion) to “shell-tunneling” spectroscopy (where electrons tunnel, one at a time, through the dot). Shell-tunneling spectroscopy provides the single-particle energy leve...

The spin of an electron placed in a magnetic field provides a natural twolevel system suitable as a qubit in a quantum computer [1]. In this work, we describe the experimental steps we have taken towards using a single electron spin, trapped in a semiconductor quantum dot, as such a spin qubit [2]. The outline is as follows. Section 1 serves as an introduction into quantum computing and quantum...

Spin states of the electrons and nuclei of phosphorus donors in silicon are strong candidates for quantum information processing applications given their excellent coherence times. Designing a scalable donor-based quantum computer will require both knowledge of the relationship between device geometry and electron tunnel couplings, and a spin readout strategy that uses minimal physical space in...

We report on a quantum dot device design that combines the low disorder properties of undoped SiGe heterostructure materials with an overlapping gate stack in which each electrostatic gate has a dominant and unique function-control of individual quantum dot occupancies and of lateral tunneling into and between dots. Control of the tunneling rate between a dot and an electron bath is demonstrate...

We consider the system of an electronic quantum dot with a base set of discrete single-particle levels due to quantization effects in an arbitrarily given attractive potential. Intradot electron-electron interaction is described employing the full many-particle Coulomb interaction Hamiltonian in second quantization. Interaction effects arising from a capacitive response of the environment is in...

Phonon-assisted electronic tunneling is studied through a double quantum dot coupled in parallel to ferromagnetic electrodes. The current voltage characteristics for the system are derived within the nonequilibrium Green function technique based on equation of motion. It is found that additional phonon-induced resonance peaks appear in the spectral function on both sides of the main resonances ...

ABSTRACT This paper describes new quantum-dot circuits that measure a Hamming distance by using the Coulomb repulsion effect between quantum dots. Measuring similarity between patterns expressed by a Hamming distance is a basic function for various information processing. Quantum dot structures realizing these circuits are also proposed, which will be constructed by using the well-controlled na...

We report a numerical study of transport properties of a quantum dot with superconducting leads. We introduce a general phenomenological model of quantum dot transport, in which electron tunnel rates are computed within the Fermi's Golden Rule approach. The low temperature current-voltage (I-V) characteristics are in qualitative agreement with experimental observations of Ralph et al. our resul...