Universal Nonadiabatic Control of Small-Gap Superconducting Qubits

Traditional electronic and communication devices operate by processing binary information encoded as bits. Such digital devices have led to the most advanced technologies that we encounter in our everyday lives and they influence virtually every aspect of our society. Nonetheless, there exists a much richer way to encode and process information. By encoding information in quantum mechanical states as qubits, phenomena such as coherence and entanglement can be harnessed to execute tasks that are intractable to digital devices. Under this paradigm, it should be possible to realize quantum computers, quantum communication networks and quantum sensors that outperform their classical counterparts. The electronic spin states of color-center defects in the semiconductor silicon carbide have recently emerged as promising qubit candidates. They have long-lived quantum coherence up to room temperature, they can be controlled with mature magnetic resonance techniques, and they have a built-in optical interface operating near the telecommunication bands. In this thesis I will present two of our contributions to this field. The first is the electric-field control of electron spin qubits. This development lays foundation for quantum electronics that operate via electrical gating, much like traditional electronics. The second is the universal control and entanglement of electron and nuclear spin qubits in an ensemble under ambient conditions. This development lays foundation for quantum devices that have a built-in redundancy and can operate in real-world conditions. Both developments represent important steps towards practical quantum devices in an electronic grade material.

Effect of Changing Dietary Energy Levels and Environmental Temperatures on Feed Consumption and Egg Production of Single Comb White Leghorns

Generalized Landau-Zener formula for non-adiabatic transitions between degenerate states

A property called entanglement entropy helps to describe the quantum states of interacting particles, and it has at last been measured. The findings open the door to a deeper understanding of quantum systems. See Article p.77 Although entanglement — in which physically separate particles can behave and can be completely specified as one — is arguably the most important measure of the quantumness of a system. However, it is difficult to measure entanglement directly. Most schemes suggested so far measure it in artificial quantum systems, like ultracold quantum gases, which require reconstruction of the quantum states via tomography and are restricted to localized systems. Here the authors find a way to directly access entanglement in a delocalized, itinerant system. After preparing two identical copies of a many-body quantum state composed of rubidium atoms, the authors let these copies interfere. With a special quantum gas microscope, properties directly connected to entanglement entropy, a characteristic measure of the entanglement of the system, can be observed. This new way of measuring entanglement entropy might allow for other properties connected to entanglement and entanglement entropy to become accessible.

Non-Hermiticity and synthetic gauge fields play two fundamental roles in engineering exotic phases and dynamics in artificial quantum systems. Here, we explore the mean-field dynamics of interacting bosons in a two-leg ladder with synthetic magnetic flux and nonreciprocal hopping under the open boundary condition. In the Hermitian limit, we showcase the breakdown of the flux-driven chiral dynamics due to the nonlinear self-trapping effect. We further find that the nonreciprocity can drive the transition between chiral dynamics and antichiral dynamics. The antichiral motion is manifested as the non-Hermitian skin dynamics along the same direction on two legs that are not suppressed by the magnetic flux, while the chiral-antichiral transition is flux tunable. We also reveal the trap-skin dynamics with the coexistence of the self-tapping and skin dynamics in the ladder. Dynamical phase diagrams with respect to the chiral-antichiral dynamics, skin dynamics, self-trapping dynamics, and trap-skin dynamics are presented. Our results shed light on intriguing dynamical phenomena under the interplay among non-Hermiticity, nonlinearity, and artificial gauge fields.

We analyze the operation of a novel sensor based on atom interferometry, which can achieve supra-classical sensitivity by exploiting quantum correlations in mixed states of many qubits. The interferometer is based on quantum gates which use coherently-controlled Rydberg interactions between a single atom (which acts as a control qubit) and an atomic ensemble (which provides register qubits). In principle, our scheme can achieve precision scaling with the size of the ensemble - which can extend to large numbers of atoms - while using only single-qubit operations on the control and bulk operations on the ensemble. We investigate realistic implementation of the interferometer, and our main aim is to develop a new approach to quantum metrology that can achieve quantum-enhanced measurement precision by exploiting coherent operations on large impure quantum states. We propose an experiment to demonstrate the enhanced sensitivity of the protocol, and to investigate a transition from classical to supra-classical sensitivity which occurs when using highly-mixed probe states.

The quantization of electronic energy levels in atoms is foundational to a mechanistic explanation of the periodicity of elemental properties and behavior. This paper presents a hands-on, guided inquiry approach to teaching this concept as part of a broader treatment of quantum mechanics, and as a foundation for an understanding of chemical behavior. The approach is centered around two laboratory experiments in which students use light emitting diodes (LEDs) to test hypotheses related to the quantization of energy levels. In the first experiment, students determine the relationship between the voltage required to light a series of LEDs and the wavelength of the light emitted. In the second experiment, they determine the relationship between the intensity and wavelength of a series of LEDs to the intensity of the glow produced by a piece of phosphorescent material exposed to those LEDs. From the experiments and guided discussion, the students can build a solid understanding of the quantization of energy levels and transitions in atoms. This can provide them with a firm foundation on which to build their understandings of quantum mechanics and chemical behavior in general.

Feed Intake Response to Changes in Environmental Temperature and Dietary Energy in Roosters

Carbon fiber-reinforced Aluminum Laminate (CARALL) is a new generation of Fibre Metal Laminate (FML) material. This study investigates the low-velocity impact behavior of CARALL structures at different environmental temperatures (−40°C, 23°C, and 80°C). Two different groups of CARALL composite structures with varying fiber orientations were produced by hot pressing in a 3/2 arrangement: C1 (Al/0°90°/Al/90°0°/Al) and C2 (Al/0°0°/Al/0°0°/Al). Low-velocity impact tests were conducted at 23 J, 33 J, and 48 J energy levels using a Ø20 mm spherical impactor tip. The area of damage was detected by ultrasonic C-Scan. In addition, analysis of variance (ANOVA) was applied to reveal the influential parameters and their effect levels. After conducting experiments using the Taguchi L18 test set, it was observed that the C2-coded specimen yielded better results in terms of maximum peak load, maximum displacement, and damage area. While the decrease in temperature increased the damage and maximum peak load, the increase in temperature did not cause a significant change in the maximum peak load. The primary damage mechanisms observed in damage investigations were matrix cracks and delamination between composite layers. Although delamination is present between the Al/CFRP layer, it is not significant. According to ANOVA results, impact energy was the most effective parameter for maximum impact force, maximum displacement, and damage area, with contribution rates of 81%, 74%, and 76%, respectively. The optimal experimental conditions (23°C temperature and 23 J impact energy with the C1-coded sample) were determined using grey relational analysis based on principal component analysis.

The ZX-calculus is a graphical calculus for reasoning about pure state qubit\nquantum mechanics. It is complete for pure qubit stabilizer quantum mechanics,\nmeaning any equality involving only stabilizer operations that can be derived\nusing matrices can also be derived pictorially. Stabilizer operations include\nthe unitary Clifford group, as well as preparation of qubits in the state |0>,\nand measurements in the computational basis. For general pure state qubit\nquantum mechanics, the ZX-calculus is incomplete: there exist equalities\ninvolving non-stabilizer unitary operations on single qubits which cannot be\nderived from the current rule set for the ZX-calculus. Here, we show that the\nZX-calculus for single qubits remains complete upon adding the operator T to\nthe single-qubit stabilizer operations. This is particularly interesting as the\nresulting single-qubit Clifford+T group is approximately universal, i.e. any\nunitary single-qubit operator can be approximated to arbitrary accuracy using\nonly Clifford operators and T.\n

The previous chapter introduced the energy levels in simple potential fields, such as quantum wells, harmonic oscillators, atoms, and molecules. In this chapter, we will discuss energy levels in solids. We focus our discussion on single crystals, which are the simplest form of solids because the atoms are regularly arranged. As we will see, crystal periodicity plays a central role in determining the energy levels. So we will start by discussing crystal structures, including lattices and the potentials binding the atoms into a crystal. Since atoms in solids are packed closely, the electron wave functions of individual atoms overlap and form new wave functions and, correspondingly, new electron energy levels. The interatomic forces bond nuclei together so that the vibration of the atoms inside the crystal is strongly coupled. The collective atomic vibration can be decomposed into normal modes extending over the crystal and the basic energy quantum of each normal mode is called a phonon, in the same way of that the basic energy quantum of an electromagnetic mode is called a photon. Each electron and phonon wave function is characterized by a frequency (or energy) and a wave vector. The relationship between the energy and the wave vector is called the dispersion relation, which plays a central role in determining the properties of the crystal. We limit mathematical derivations to the dispersion relations of electrons and phonons in one-dimensional periodic structures and explain the energy levels in real crystals without a more detailed mathematical derivation, because the dispersion relation in a real crystal can be appreciated on the basis of a sound understanding of the behavior of a one-dimensional periodic system. The energy levels in crystals are highly degenerate. A very useful tool that takes into account the degeneracy of the energy states is the density of states, which will be used repeatedly throughout the book and should be mastered.

f (R) theories are the simplest generalisations of General Relativity, Einstein’s theory of gravity. f (R) theories, and modified gravity theories more broadly, have been invoked to explain the accelerated expansion of the universe. A number of “viable” models have been proposed which satisfy cosmological tests and get around present day laboratory and solar system constraints by invoking the chameleon mechanism. It is important to determine whether such alternative models can be distinguished by precision experiments at the laboratory scale. This thesis focuses on recently proposed f (R) models in the context of the upcoming neutron quantum bouncer experiment GRANIT [1], which has the potential to directly observe violations of Einstein gravity. This experiment works by precisely measuring the energy levels of ultra-cold neutrons trapped in the Earth’s gravitational field above a mirror. Neutrons in these states have energies of the order of 10−12 eV (peV) and wavefunctions with spatial extents of ∼ 10 μm. The size of the neutron wavefunctions gives gravitational spectroscopy sensitivity to any change of the Newtonian potential above the mirror surface on a scale of tens of microns. These experiments have a unique opportunity to study gravity and quantum mechanics in an unprecedented regime. GRANIT claims an energy sensitivity of 0.01 peV with an improvement of one or two orders of magnitude expected over the next several years. The theoretical limit to the sensitivity is 10−7 peV. Previous work by Brax and Pignol [2] has shown that scalar-tensor theories, which are closely related to f (R) theories, can give rise to detectable shifts in the energy levels from their Newtonian values. Here the energy levels shifts are examined for three viable f (R) models: the exponential gravity model of Linder [3], the model of Hu and Sawicki [4] and the “new” exponential gravity model of Xu and Chen [5]. It is found that exponential gravity predicts energy level shifts of the order exp ( −10 ) mNc , where mN is the neutron mass. This is unobservable in any experiment lasting less than the age of the universe. The Hu-Sawicki model predicts much larger shifts which depend on the model parameters n and c2, where n, c2 > 0. It is found that the shifts are below the theoretical sensitivity limit for n ≥ 1 2 , with shifts at n = 1 2 of the order of 10 −19 peV. It is unlikely, though not yet ruled out, that n 1 models could be observed at neutron bouncer experiments operating under extreme conditions. The computation of the shifts for n 1 models is hampered by convergence issues. This may be immaterial, however, because Hu-Sawicki models with n 2 Hu-Sawicki model at laboratory scales, hence it is unobservable at a neutron bouncer experiment. The reason for the difference between these results with those of Brax and Pignol is shown to be due to the special form of the scalar potential and matter coupling, which are free in scalar-tensor theory and can be chosen to give a large effect, but are constrained in f (R) gravity. Because of these special features the neutron bouncer experiment can distinguish between f (R) and non-f (R) modified gravity, but not between the f (R) models examined in this thesis. Note the original date of this thesis was 22 November 2012. This version, with several copyrighted figures removed but nothing else modified apart from this notice, was created 21 October 2014.

Correlation of experimental and theoretical data for artificial and natural systems with immobilized biocatalysts

In this paper, we analyse the propagation of a short light pulse through a 1D quantum metamaterial structure, composed of arranged artificial two-level quantum systems. We set up the model which material substance is treated quantum mechanically, while the electromagnetic pulse is classical. On the basis of the adopted model, we investigate the short light pulse propagation through the structure in dependence on the initial state of irradiated two-level systems, the amplitude of the incident light pulse, and the frequency of the pulse carrier wave. Finally, we determine the regimes when the incident pulse can propagate in undistorted soliton form.

The concept of non‐Hermitian systems, also known as exceptional points (EPs), has recently emerged as a novel approach for designing the response of systems that exchange energy with the external environment. The system behaves as a non‐Hermitian Hamiltonian (NH Hamiltonian), the real part of which is related to the internal dynamics of the system, and the imaginary part reflects the energy exchange between the system and the outside environment. By utilizing double EIT windows and adjusting the intensity of the dressing field, the number and positions of eigenvalues can be modulated to construct quantum entanglement sources for non‐Hermitian systems, thereby laying the foundation for quantum communication and quantum computing. To prepare photon entanglement sources, it is necessary to study the correlation of high‐dimensional quantized energy levels under PT symmetry and symmetry breaking induced by the dressing field; Hamiltonian correlation matrix of the non‐Hermitian system characterizes the relationship between gain and loss, detuning and dephasing rate in the reaction energy‐level system, and the coupling relationship of the dressing field. The energy‐level system itself is non‐Hermitian, and the study of symmetry breaking is conducted by controlling EPs during the level control process through the dressing field, thus eliminating the need for introducing artificial photonic structures. The third‐order non‐Hermitian characteristics of the PT‐NH system reflect the positional relationship between the cascade field and the nested field. When the Rabi frequency (dephase rate) of the dressing field is the dominant factor, the real (imaginary) part of the eigenvalues is split, resulting in in‐phase (out‐of‐phase) constructive (destructive) transformations of the dressing order.