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Popular Abstract in Swedish Denna avhandling behandlar tillväxt av och elektriska mätningar på halvledande nanotrådar av indiumarsenid (InAs) och kombinationer av InAs och indiumfosfid (InP). En nanotråd är som namnet antyder en tunn solid tråd, som påminner om ett hårstrå fast med en diameter på typiskt 50 nm (en nanometer är en miljarddels meter, 10^-9 m) och längden kan vara allt från 100 nm upIn this thesis, semiconductor nanowires are studied from the point of view of growth and electrical properties. The growth of nanowires is done by chemical beam epitaxy (CBE), an ultra-high vacuum technique allowing a precise control of precursor deposition and low growth rates. In conventional epitaxy, growth is usually two or three- dimensional, depending on growth conditions and material combin

We use the exact strong-interaction limit of the Hohenberg-Kohn energy density functional to construct an approximation for the exchange-correlation term of the Kohn-Sham approach. The resulting exchange-correlation potential is able to capture the features of the strongly correlated regime without breaking the spin or any other symmetry. In particular, it shows "bumps" (or barriers) that give ris

Artificial Kitaev chains, formed by quantum dots coupled via superconductors, have emerged as a promising platform for realizing Majorana bound states. Even a minimal Kitaev chain (a quantum dot-superconductor-quantum dot setup) can host Majorana states at discrete sweet spots. However, unambiguously identifying Majorana sweet spots in such a system is still challenging. In this work, we propose a

Programmable optical circuits are an important tool in developing quantum technologies such as transceivers for quantum communication and integrated photonic chips for quantum information processing. Maintaining precise control over every individual component becomes challenging at large scales, leading to a reduction in the quality of operations performed. In parallel, minor imperfections in circ

Quantum chromodynamics (QCD), the basic theory of strong interactions between the quarks and gluons is expected to play an important role in the early universe. We discuss the scenario when the fast cooling of QCD matter leads to the creation of a saturated phase with an enormous number of possible configurations. Using an analogy with the classical glasses we predict that this glassy form of matt

Scale invariance and self-similarity in physics provide a unified framework for classifying phases of matter and dynamical properties near equilibrium in both classical and quantum systems. This paradigm has been further extended to isolated many-body quantum systems driven far from equilibrium, for which the physical observables exhibit dynamical scaling with universal scaling exponents. Universa

This thesis investigates the quantum Mpemba effect, where an initially hotter system cools down faster than an initially colder one. This was demonstrated in a qubit system coupled to two environments. A thermal state is chosen as the initial state and then left to freely equilibrate. It was shown that the initial thermal state can be chosen in a way to accelerate the resulting relaxation process.

After reviewing basic concepts and tools in order to quantify entanglement, a theoretical set up is proposed, which is based on the double slit experiment and the Mach-Zehnder interferometer. A particle, which is in a superposition of two paths, can interfere with a qubit on each path before it is scattered by a beam splitter and measured by two separate detectors. After a detailed investigation,

We use a scanning gate microscope (SGM) to characterize one-dimensional ultra-thin (diameter approximate to 30 nm) InAs/InP heterostructure nanowires containing a nominally 300 nm long InAs quantum dot defined by two InP tunnel barriers. Measurements of Coulomb blockade conductance versus backgate voltage with no tip present are difficult to decipher. Using the SGM tip as a charged movable gate, w

The conjugated polymer poly(2-methoxy-5-(2'-ethylhexyloxy)-1,4-pheiiylene vinylene) (MEH-PPV) was studied by a single-molecule imaging technique. A comparison of statistical distributions of fluorescence intensity with molecular weight distributions revealed that the distribution of the photoluminescence quantum yield of the single polymer chains under study is significantly asymmetric, with a pol

We have performed photoluminescence spectroscopy on single GaAs nanowires with InAs quantum dots in the form of thin slices of InAs, possibly alloyed with Ga as InGaAs, incorporated into the GaAs. The nanowires were grown by chemical beam epitaxy using gold nanoparticles as catalysts. The photoluminescence measurements showed rich spectra consisting of sharp lines with energies and excitation powe

We use a microscopic Slater-Koster tight-binding model to study the magnetic properties of ferromagnetic metal nanoparticles containing up to 260 atoms. We compute the total energy as a function of the magnetization direction and the ensuing magnetic anisotropy. In an external magnetic field, the ground-state energy as a function of the magnetization orientation is characterized by minima separate

This study has observed and investigated random telegraph noise in the photoluminescence from InAs quantum dots in GaAs and InP quantum dots in GaInP. The dots are grown by the Stranski-Krastanow technique with a sufficiently low surface density that individual dots easily could be investigated. The luminescence from many single quantum dots, exhibiting switching between two levels, has been spect

Semiconductor nanowires have great potential for realizing broadband photodetectors monolithically integrated with silicon. However, the spectral range of such detectors has so far been limited to selected regions in the ultraviolet, visible, and near-infrared regions. Here, we report on the first intersubband nanowire heterostructure array photodetectors exhibiting a spectrally resolved photoresp