Quantum computing is an emerging technology, which holds the potential to simulate complex quantum systems beyond the reach of classical numerical methods.Despite recent formidable advancements in... Show moreQuantum computing is an emerging technology, which holds the potential to simulate complex quantum systems beyond the reach of classical numerical methods.Despite recent formidable advancements in quantum hardware, constructing a quantum computer capable of performing useful calculations remains challenging.In the absence of a reliable quantum computer, the study of potential applications relies on mathematical methods, ingenious approximations, and heuristics derived from the fields of application. This thesis focuses on developing new quantum algorithms, targeting some of the key challenges in the simulation of complex quantum systems.The techniques introduced in this thesis span from quantum state preparation to mitigation of hardware and algorithmic noise, from efficient expectation value measurement to noise-resilient applications in quantum chemistry. A common thread connecting all these algorithms is the introduction of a single auxiliary qubit – a fundamental unit of quantum information – which has an active and distinctive role in the task at hand. Show less
Biological cells, the basic building blocks of all life forms, are surrounded by a lipid membrane. More than half of the membrane is occupied by membrane proteins, which can regulate the cell... Show moreBiological cells, the basic building blocks of all life forms, are surrounded by a lipid membrane. More than half of the membrane is occupied by membrane proteins, which can regulate the cell functionality through specific arrangements. To regulate the arrangements several proteins have to work together. In addition to direct forces, there exists an indirect force between the proteins, which stems from their deformation of the membrane and contributes to their self-organization. Since the actual membrane is very crowded and proteins are too tiny and complex to measure this interaction, in this thesis we used a model system consisting of lipid membranes and solid particles to study the deformation-mediated interaction. We experimentally confirmed for the first time that, unlike many known forces, this deformation-mediated interaction is not additive, i.e. the strength and range of three (or more) deformations cannot be obtained by simple addition of the interactions between pairs of deformations. We found that the interaction weakens with increasing number of membrane-deforming particles and that the particle become less ordered. We investigated deformations in both directions of the membrane and found that the interaction can be both repulsive and attractive, and furthermore depends on the shape of the deformation. This thesis helps to better understand the organization of proteins that deform cellular membranes. Show less
Detecting nanoscopic objects plays an important role in nanoscience in particular, in the rapidly growing field of nanobiology. The forebear to modern super-resolution microscopy for single... Show moreDetecting nanoscopic objects plays an important role in nanoscience in particular, in the rapidly growing field of nanobiology. The forebear to modern super-resolution microscopy for single molecule investigation, is fluorescence microscopy. Fluorescence as a contrast mechanism, however, brings several restrictions. These include (1) the use of the label itself, which may introduce artifacts to the interpretation, (2) the limited photoemission caused by photobleaching and photoblinking as well as (3) low bandwidth of the emission. Fluorescence-free alternatives are thus highly desirable to overcome these limitations. Optical detection of individual proteins with high bandwidth holds great promise for understanding important biological processes on the nanoscale. In this thesis, we investigate label-free optoplasmonic detection of single proteins and particles in motion. Analysing the data provide information about the hydrodynamic volume of the diffuser and interaction such as binding events. Show less
A single self-assembled semiconductor quantum dot in a high-finesse optical microcavity - the subject of this thesis - is an interesting quantum-mechanical system for future quantum applications.... Show moreA single self-assembled semiconductor quantum dot in a high-finesse optical microcavity - the subject of this thesis - is an interesting quantum-mechanical system for future quantum applications. For instance, this system allows trapping of an extra electron and thus can serve as a spin quantum memory, or enables high-fidelity and high-rate single-photon production. We investigate several aspects in this thesis:First, the operation and manipulation of the system is achieved using resonant laser spectroscopy. This requires filtering out of the relatively strong excitation laser, which is often done using the cross-polarization technique. This approach, however, is complicated in optical setups by spin-orbit coupling of light at the beamsplitter. We experimentally firstly explore this effect in a cryogenic optical microscope and demonstrate its importance for quantum dot based single photon sources. Next, we develop a unique setup with a cold permanent magnet and firstly realise trapping of a single electron in our particular quantum dot - cavity devices and show spin control. Then we show how true single photons from our device can be used to create novel quantum states of light. First, we investigate theoretically single photon addition to coherent laser light including several experimental imperfections - we find an universal behaviour of the photon correlation function. Finally, we demonstrate entanglement of several consecutive photons by repeatedly using Hong-Ou-Mandel quantum interference of single photons with a photon quantum memory in the form of an optical delay loop. We show that this results in quantum states of light that have Poissonian photon statistics like laser light - therefore we call them artificial coherent states - but also that they are more complicated than ordinary coherent states and contain multi-photon quantum entanglement in the form of linear cluster states, a potential resource for universal quantum computing. Show less
The first direct detection of gravitational waves opened the possibility of mapping the Universe via this new and independent messenger. Indeed, during their propagation, gravitational waves pick... Show moreThe first direct detection of gravitational waves opened the possibility of mapping the Universe via this new and independent messenger. Indeed, during their propagation, gravitational waves pick up information about the spacetime as they are affected by its expansion and by the matter structures along the propagation path. The aim of this Thesis is to investigate which cosmological information is accessible from a gravitational wave detection, with a specific interest in the late time Universe. Show less
Mechanical metamaterials are carefully engineered materials whose properties are controlled by their structure, not by their composition, which allows using metamaterials to study and control... Show moreMechanical metamaterials are carefully engineered materials whose properties are controlled by their structure, not by their composition, which allows using metamaterials to study and control physical effects in detail. Here we develop metamaterials to study the sequential, complex response of frustrated materials that are cyclically driven. In particular, we focus on metamaterials that act as collections of hysteretic, bistable elements called hysterons. We create hysterons in metamaterials by using local frustration at defects and by using a competition between two global, incompatible deformations modes. We show how we can tune these hysterons, both by rational design and by using spatial gradients in the mechanical driving. Then we show that collectively, our samples exhibit complex transition pathways, including those with avalanches, and study the role of hysteron interactions. Finally, we explore how to control the frustration by local defects in so-called monoholar metamaterials. Show less
In this thesis, we have used numerical approaches to study the effects of translational symmetry breaking on strange metallic systems as realised by the holographic duality. This involves solving... Show moreIn this thesis, we have used numerical approaches to study the effects of translational symmetry breaking on strange metallic systems as realised by the holographic duality. This involves solving for large-scale coupled partial differential equations, describing the physics of corrugated black holes in negatively curved space-times.We show that the strong-coupling nature of the physics of these holographic systems produces some unique behaviours, which are suggestively close to experimental observations that have been done in the lab. We speculate that strong-coupling physics is what is at the heart of the mysteries that shroud the strange metal. Show less
In this thesis I describe the results of Pulsed Interleaved Excitation and Fluorescence (Cross) Correlation Spectroscopy (PIE-F(C)CS) combined with single-pair Förster Resonance Energy Transfer ... Show moreIn this thesis I describe the results of Pulsed Interleaved Excitation and Fluorescence (Cross) Correlation Spectroscopy (PIE-F(C)CS) combined with single-pair Förster Resonance Energy Transfer (spFRET) used to study dynamics in single nucleosomes, which depends on subtle differences in the length of DNA ends, DNA sequence, histone variants and specific and non-specific protein interactions. This technique, which can resolve distances between two fluorophores of only a few nanometers, is an excellent technique to monitor changes in nucleosomal compaction, as the nucleosome is only ten nanometers in diameter. In combination with F(C)CS and PIE, spFRET makes it possible to monitor conformational dynamics on a timescale of micro- to milliseconds. Show less
The Standard Model (SM) of particle physics fails to explain several observed phenomena and is incomplete. In order to resolve this problem, one may extend the SM by adding new particles. However,... Show moreThe Standard Model (SM) of particle physics fails to explain several observed phenomena and is incomplete. In order to resolve this problem, one may extend the SM by adding new particles. However, yet they have not been observed, and currently, the scientific community tries to find a signature that manifests the existence and properties of such particles. This thesis is devoted to exploring the parameter space of Feebly Interacting new physics Particles (FIPs) in a model-independent fashion using two complementary approaches. The first one is searching for FIPs at next-generation accelerator experiments called Intensity Frontier experiments. The second one is constraining the parameter space of FIPs by considering their possible impact on the observables coming from the Early Universe - Big Bang Nucleosynthesis and Cosmic Microwave Background, which are in good agreement with the predictions of the cosmological models with SM particles. They are, therefore, very sensitive to the possible existence of FIPs in the primordial plasma. As a result of the researches constituting this thesis, novel model-independent results, as well as constraints on particular models of FIPs such as Heavy Neutral Leptons, have been obtained in both of these areas. Show less
This thesis aims to improve the detection from ultra-weak single emitter by enhancing their emission properties with plasmonic nanostructures. We exploit the wet-chemically synthesized single... Show moreThis thesis aims to improve the detection from ultra-weak single emitter by enhancing their emission properties with plasmonic nanostructures. We exploit the wet-chemically synthesized single crystalline gold nanorods (GNRs) as our basic frameworks in the whole studies, simply because of their unique optical properties, such as the intense electromagnetic fields enhancement near the tips, and the narrow, tunable resonance with light. We first explore the lower limit of fluorescence quantum yield for single-molecule detection by enhancing the fluorescence with a single gold nanorod. Later, we develop a method to synthesize end-to-end gold nanorod dimers on glass substrates with the aid of molecular linkers, and then apply these strong plasmon coupling systems to enhance the single-molecule fluorescence under two-photon excitation. Show less
Systems with local constraints is a new finding in recent researches on complex systems. The heterogeneous spatial interactions and the temporal dependencies among those numerous units make it... Show moreSystems with local constraints is a new finding in recent researches on complex systems. The heterogeneous spatial interactions and the temporal dependencies among those numerous units make it difficult to describe by traditional statistical physics.These complex structures also make information storage and transmission in it is impossible to describe by the random variables with finite outcomes in the classical information theory. In this thesis, we use the statistical ensemble with local constraints to describe those complex systems with heterogeneous interactions and dependencies. This description also helps us find the new information-theoretical bounds in the systems with local constraints, even when the temporal dependencies among numerous units break the asymptotic equipartition property in the classical information theory.Furthermore, we find that the breaking of ensemble equivalence generally exists in systems with local constraints even without the presence of phase transition, and this ensemble nonequivalence in the systems with local constraints without phase transition can be the same strong as the one that only appears on the boundary of phase transitions caused by the long-range interactions. We also find that this breaking of ensemble equivalence will affect the limit of information storage and transmission in systems with local constraints.These results in this thesis extend our understanding of complex systems and information theory. Show less
In this thesis we use Josephson and noise scanning tunneling microscopy for the study of conventional, unconventional (iron-based) and disordered superconductors. On the one hand, Josephson... Show moreIn this thesis we use Josephson and noise scanning tunneling microscopy for the study of conventional, unconventional (iron-based) and disordered superconductors. On the one hand, Josephson scanning tunneling microscopy allows us to directly visualize the superfluid density with high spatial resolution. On the other hand, noise scanning tunneling microscopy is employed for measuring the shot noise which detects the charge of the carriers forming a superconducting condensate. Show less
The elementary excitations of magnets are called spin waves, and their corresponding quasi-particles are known as magnons. The rapidly growing field of Magnonics aims at using them as information... Show moreThe elementary excitations of magnets are called spin waves, and their corresponding quasi-particles are known as magnons. The rapidly growing field of Magnonics aims at using them as information carriers in a new generation of electronic devices, (almost) free of electric currents. Encoding information in the amplitude and/or phase of these coherent waves could lead to a drastic decrease in dissipated power, typically related to the motion of electrons ("Joule" or "Ohmic" heating).This dissertation describes the development and use of a new technique to study spin waves. This technique uses the electronic spins associated with nitrogen-vacancy (NV) centers as magnetic field sensors. An NV center is a light-emitting defect in the crystal lattice of diamond. Remarkably, the brightness of its emission depends on its spin state, sensitive to magnetic fields. This way, magnetic information can be investigated optically. Show less
This thesis is dedicated to the exploration of the primordial dark ages: unknown physics during the earliest stages of the Universe’s expansion that have not yet been directly probed by... Show moreThis thesis is dedicated to the exploration of the primordial dark ages: unknown physics during the earliest stages of the Universe’s expansion that have not yet been directly probed by observations. Cosmic inflation is a burst of exponential expansion of space after the “Big Bang”. The energy that drives inflation must be transferred to elementary particles and radiation. This process is called reheating. The unknown expansion history of the universe during the reheating era connects the cosmic microwave background (CMB) observations to inflationary physics. CMB is a relic radiation that provides us a snapshot of the primordial universe. Both the inflationary and reheating eras generate signatures to be seen via upcoming gravitational waves and CMB polarization experiments. In this thesis we show analytically a scaling behaviour that allows for an easy estimate of the reheating efficiency for one broad family of multi-field models of inflation that is called α-attractors. We show the influence of the asymmetry around the minimum of potential on the reheating efficiency. Moreover, we study the predictions for chiral gravitational waves production by a spectator gauge field sector in scalar single-field inflation. Finally, we present a new class of inflationary models that is called “shift-symmetric orbital inflation”. Show less
Synthetic microswimmers take an important place within the interdisciplinary field of active soft matter. Many efforts are being made to develop, understand and ultimately control them, because of... Show moreSynthetic microswimmers take an important place within the interdisciplinary field of active soft matter. Many efforts are being made to develop, understand and ultimately control them, because of their great potential for fundamental studies and applications. A widely employed type is that of catalytically propelled microswimmers, such as platinum-half-coated colloids which achieve self-propulsion in aqueous hydrogen peroxide environments via a catalytic reaction taking place on the platinum. Surprisingly, although these swimmers are typically found self-propelling parallel to walls, the origins for this near-wall behavior and the influence of the walls are still largely unexplored. In this thesis, we examine the behavior of catalytic microswimmers near walls. We find that the physical property of slip of the nearby wall significantly impacts their speed. We develop a new diffusion-based analysis method, and uncover that swimmers tend to fixed heights above planar walls. Using obstacles of different shapes 3D-printed on the planar wall, we found cooperative swimmer behaviors along one-dimensional environments. Overall, our findings provide new insights into the still-debated propulsion mechanism of catalytic microswimmers, and may also aid in predicting and controlling swimmer motions in future applications, where synthetic swimmers will be needed to perform tasks inside complex environments. Show less
We have studied the impact of particle shape anisotropy, multivalent interactions and flexibility on systems of micron-sized colloidal particles. In short, we have characterized the diffusive... Show moreWe have studied the impact of particle shape anisotropy, multivalent interactions and flexibility on systems of micron-sized colloidal particles. In short, we have characterized the diffusive properties of anisotropic dumbbell particles near surfaces. Furthermore, by using experiments and simulations, we have uncovered marked flexibility-induces effects in the Brownian motion of reconfigurable colloidal structures. Our work demonstrates the rich dynamics and possibilities for applications of shape-changing colloidal systems. We hope our findings further the study of the diffusivity of flexible objects found in complex mixtures relevant in, for example, the cosmetic, pharmaceutical and food industries, as well as in biological and drug-delivery systems. For example, our results may have implications for understanding both the diffusive behavior and the most likely conformations of macromolecular systems such as polymers, single-stranded DNA and other chain-like molecules. Show less
Errors are everywhere, and mechanical failures are especially common: buckled grain silos and cracked support columns are, justly, seen as an issue to be avoided. But flaws can also be used to... Show moreErrors are everywhere, and mechanical failures are especially common: buckled grain silos and cracked support columns are, justly, seen as an issue to be avoided. But flaws can also be used to design materials with unique functionalities. In the work presented here, we use two types of imperfections to create functional structures. First, we design materials that are locally stiff or soft, depending on how they are actuated, using topological imperfections: mistakes in their underlying architecture. Second, we create structures that shape-morph, because their individual elements fail, buckle, and snap- features that should be avoided otherwise. Show less
The human body consists of hundreds, perhaps thousands of different types of cells, each with different morphologies and functions, despite having the same genome. This diversity is created by gene... Show moreThe human body consists of hundreds, perhaps thousands of different types of cells, each with different morphologies and functions, despite having the same genome. This diversity is created by gene regulation, a set of mechanisms that determine, which genes are used to make proteins and which genes are kept silent. During embryonic development, gene are turned on and off in a tightly orchestrated manner, to make sure that the right cell type is created at the right time and place.In this thesis we report several studies pertaining to gene regulation in embryonic development. Each of the four chapters will cover a different layer of the gene regulation toolbox: gene inactivation by DNA methylation, transcriptional regulation in the developing kidney, regulation of protein turnover and translational regulation through micro-RNAs. Together, these studies provide a refined understanding of the crucial role of gene regulation for embryonic development. Show less
This dissertation is an experimental study of laser-generated, atmospheric pressure, transient toroidal helium plasmas.The formation mechanism of these toroidal plasmas is identified and an... Show moreThis dissertation is an experimental study of laser-generated, atmospheric pressure, transient toroidal helium plasmas.The formation mechanism of these toroidal plasmas is identified and an estimate of their main plasma parameters is obtained. Furthermore, preliminary experiments are presented, aimed at heating these plasmas by absorption of microwave radiation, in order to counteract their transient nature.Through a tomographic reconstruction, cross-sectional images of the toroidal plasma are obtained, visualising the fluid flow responsible for the generation of the toroidal structure. The origin of the flow is traced back to the structure of the plasma kernel. The shocks generated by this kernel interact akin to a Mach reflection and generate a low pressure region whose replenishment transforms the plasma into a toroid. Schlieren imaging, complemented with a novel scanning-probe technique, and thermodynamic modelling, as well as deliberately breaking the flow symmetry, confirm the formation mechanism. A high-power, sub-microsecond rise time, pulsed magnetron source has been designed for the microwave heating experiments. Its detailed design and the effect of the microwave pulse on the plasma are discussed.This work is part of a larger study on self-organising knotted magnetic structures in plasma, which may find their application in nuclear fusion and astrophysical research. Show less
