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In this thesis, crystals of yttrium orthosilicate (Y2SiO5) that are randomly doped with another rare-earth element, such as praseodymium (Pr), europium (Eu), or cerium (Ce), are investigated with lasers locked to ultra-stable cavities using the Pound-Drever-Hall locking technique. Many of these rare-earth elements have long-lived 4f-4f transitions, hundreds of microseconds to a few milliseconds, w

We address the problem of the dissipative character of collective motion in finite Fermi systems. We study this problem from the point of view of chaotic features of the fermionic degrees of freedom of the many-body Fermi systems. Our main aim is of two kinds: first, we investigate how quantum chaos sets in in many-body systems and then, we try to relate quantum many-body chaos of the intrinsic fe

Bound states in quantum dots coupled to superconductors can be in a coherent superposition of states with different electron number but with the same fermion parity. Electrostatic gating can tune this superposition to a sweet spot, where the quantum dot has the same mean electric charge independent of its electron-number parity. Here, we propose to encode quantum information in the local fermion p

https://www.sljus.lu.se/research-landing-page/magnetism-and-superconductivity - 2026-07-21

Wave packet interferometry with vacuum ultraviolet light has been used to probe a complex region of the electronic spectrum of molecular nitrogen, N2. Wave packets of Rydberg and valence states were excited by using double pulses of vacuum ultraviolet (VUV), free-electron-laser (FEL) light. These wave packets were composed of contributions from multiple electronic states with a moderate principal

Supersolids formed from dipolar Bose Einstein condensates (BECs) exhibit spontaneous density modulation while maintaining global phase coherence. This state of matter supports gapped amplitude (Higgs) excitations featuring a quadratic dispersion relation. While Higgs modes are typically strongly damped due to coupling with other amplitude and phase modes, imposing an experimentally realistic toroi

In modern building construction, where light weight structures are preferred for cost reasons, the sound transmission is often a problem to be considered carefully, hence the many studies addressing this issue. Various modal methods are frequently used to investigate the vibration pattern of light weight building structures in the low frequency range. The experimental determination of time average

Introduction: Gender imbalances in academia are found globally. Even though women earn the same rate of PhD degrees, the gender imbalance becomes increasingly prominent at higher academic levels. Several reasons have been proposed for these differences, including family responsibilities, disparities in the number and size of grants awarded, invitations to present at conferences, and differences in

The rise of MEMS and µTAS techniques has created a whole new family of microfluidic devices for a wide range of chemical and biomedical analyses to be performed on small Lab-on-a-chip platforms. The operations often include small samples of particle or cell suspensions on which separation, mixing, trapping or sorting is performed. External fields and forces are used for these operations, and this

The crucial step in the conversion of solar to chemical energy in photosynthesis takes place in the reaction centre, where the absorbed excitation energy is converted into a stable charge-separated state by ultrafast electron transfer events. However, the fundamental mechanism responsible for the near-unity quantum efficiency of this process is unknown. Here we elucidate the role of coherence in d

The study of electronic transport in chemically synthesized semiconductor nanowires is an active field of research, with potential applications in areas such as quantum computing and nanoelectronics. Motivated by recent experimental progress, we use a simple non-atomistic tight-binding model implemented in open-source software to simulate quantum electronic transport in such nanowires. Including v

We provide a simple set of rules for predicting interference effects in off-resonant transport through single molecule junctions. These effects fall into two classes, showing, respectively, an odd or an even number of nodes in the linear conductance within a given molecular charge state, and we demonstrate how to decide the interference class directly from the contacting geometry. For neutral alte

Realization of robust coherent quantum phase slips represents a significant experimental challenge. Here we propose a design consisting of multiple nanowire junctions to realize a phase-slip flux qubit. It admits good tunability provided by gate voltages applied on superconducting islands separating nanowire junctions. In addition, the gates and junctions can be identical to or distinct from each

Attofysik är förankrad i ljus-materia växelverkan som uppkommer från starka fält, vilken gör det möjligt att generera, kontrollera och mäta elektroners dynamik på deras naturliga tidsskala. Kvantsammanflätning och koherens mellan fotoelektron och jon i laserassisterad ultrasnabb fotojonisation är väsentliga för att kunna förstå den underliggande dynamiken och kontroll över det korrelerade tvådeladAttosecond physics is embedded in strong-field light-matter interactions, which enable the generation, control, and measurement of electron dynamics on their natural timescale. The entanglement and coherence between the photoelectron and ion in laser-assisted ultrafast photoionisation are fundamental to understanding the underlying dynamics and control of the correlated bipartite system. This work

Den här avhandlingen berör två olika forskningsområden som är relaterade till fysiken för nanosystem. Det första området rör kvantkorrelationer och sammanflätning mellan elektroner i nanosystem, med ett särskilt fokus på hur man kan generera elektronisk orbital sammanflätning på tidsskalor mycket kortare än dekoherenstiden och hur man kan göra detektionen av sammanflätning enklare experimentellt. This thesis addresses two different topics related to the physics of nanoscale systems. The first topic concerns quantum correlations and entanglement between electrons in solid-state systems, with a focus on how to generate electronic orbital entanglement on a sub-decoherence time scale and how to achieve experimentally more feasible entanglement detection schemes. The second topic concerns heat

Recently, nonlinear properties of three-terminal ballistic junctions (TBJs) were predicted by theoretical calculations done by Xu, and potential applications such as rectification and logic function proposed. In that analysis the TBJ was modeled by connecting three quantum point contacts via a ballistic cavity with adiabatic boundaries, thus neglecting any backscattering of electrons. In this pape

Coherent light sources have been widely used in control schemes that exploit quantum interference effects to direct the outcome of photochemical processes. The adaptive shaping of laser pulses is a particularly powerful tool in this context: experimental output as feedback in an iterative learning loop refines the applied laser field to render it best suited to constraints set by the experimenter.

Quantum fluctuation of the energy is studied for an ultracold gas of interacting fermions trapped in a three-dimensional potential. Periodic-orbit theory is explored, and energy fluctuations are studied versus the particle number for generic regular and chaotic systems, as well as for a system defined by a harmonic confinement potential. Temperature effects on the energy fluctuations are investiga