Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 147 for “"Decoherence"”.
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Decoherence in infinite quantum systems
Die Quantenmechanik gilt heute als unsere grundlegendste physikalische Theorie. Als solche beschränkt sie sich nicht nur auf ihre ursprünglichen Anwendungsbereiche wie die Atomphysik, Elementarteilchenphysik und die Quantenfeldtheorie, sondern ihr Gegenstandsbereich sollte auch makroskopische …
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Decoherence of Quantum Markov Systems
… purpose of this thesis is to discuss quantum decoherence in the frame- work of operator algebras. We will define several types of decoherence of quantum Markov systems based on the original notion introduced by Ph. Blanchard and R. Olkiewicz; then we will give a number of suffiecient …
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Explorations of quantum decoherence phenomena
… the experimental exploration of quantum decoherence using discrete and continuous-time decoherence maps. The experimental methodology uses liquid-state nuclear magnetic resonance spectroscopy techniques. Initially, a brief discussion of coherent control methods is given. Then, a detailed …
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Decoherence and Dephasing of Vibronic Excitons /
… this thesis, the significance of dephasing and decoherence of vibronic excitons in molecular systems is investigated and the signatures of electronic-vibrational interaction in the two-dimensional electronic spectra are analyzed with the focus on evolution of molecular excitation and quantum …
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Semiclassical studies of decoherence produced by scattering
The conventional notion of coherent atom-surface scattering originates from the existence of Bragg peaks in elastic scattering. The helium atom acts as a quantum mechanical matter wave that is coherent with itself; the well-defined phase relationship of the particle beam at the different spatial …
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Many-body decoherence with cold atoms in optical lattices
… This thesis addresses the issue of many-body decoherence, using analytical and numerical techniques, in these optical lattice experiments that arises due to coupling to the environment. We specifically study fermionic systems to investigate the effects of incoherent light scattering on the …
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Decoherence and Dynamical Decoupling in Solid-State Spin Qubits
This dissertation is a study of the decoherence of a solid-state spin qubit, either that of a localized electron spin or a donor nucleus, caused by a nuclear spin bath relevant to semiconductor quantum computer architectures. In the presence of an external magnetic field and at low temperatures, …
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Effects of an External Field and Dissipation on Decoherence
Decoherence is the suppression of the interference of quantum states. It plays important roles in the study of the quantum-classical transition. It is also the major obstacle in the implementation of various schemes of quantum computers. Decoherence can be affected by many factors. The interactions …
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Decoherence of Transverse Electronic Spin Current in Magnetic Metals
Transport of spin angular momentum (spin currents) in magnetic thin films is important for non-volatile spin-based memory devices and other emerging information technology applications. It is especially important to understand how a spin current propagates across interfaces and how a spin current …
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Decoherence, Master Equation for Open Quantum Systems, and the Subordination Theory
… addresses the problem of a form of anomalous decoherence that sheds light into the spectroscopy of blinking quantum dots. The system studied is a two-state system, interacting with an external environment that has the effect of establishing an interaction between the two states, via a …
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Decoherence In Quantum Dot Charge Qubits: The Role Of Electromagnetic Fluctuations
… efficient single-qubit operations. However, the decoherence rates observed in the experiments is still quite high, making double dot charge qubits not very appealing for large-scale implementations. The following work describes the effect of the electromagnetic (EM) environment of the double …
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Measuring trapped-ion motional decoherence through direct manipulation of motional coherent states
… a precise knowledge of a system's motional decoherence time, or the time after which an ion's motional state is no longer reliably known or can no longer be controlled. Existing measurements of motional coherence indirectly control and measure the motional state by coupling the motional …
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Quantum dynamics in condensed phases : charge carrier mobility, decoherence, and excitation energy transfer
… approach to describe quantum dissipation and decoherence. We then applied this method to study the effect of noise in a number of quantum algorithms and calculate noise threshold for fault-tolerant quantum error corrections (QEC). In addition, we perform a systematic investigation on several …
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Measuring decoherence and the matter-wave index of refraction with an improved atom interferometer
… performed a series of experiments related to decoherence in an atom interferometer. We have explored decoherence due to photon scattering, in particular the transition from single- to multiple-photon decoherence, and have quantitatively verified the decoherence rate constant in the many-photon …
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Thermodynamic Based Framework for Determining Sustainable Electric Infrastructures as well as Modeling of Decoherence in Quantum Composite Systems
… (SEA-QT) is used to model the phenomenon of decoherence. The two smallest microscopic composite systems encountered in Nature are studied. The first of these is composed of two two-level-type particles, while the second one is composed of a two-level-type particle and an electromagnetic …
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Magic Trapping of a Three-Level System for Rydberg Quantum Computation
… The dominant problem for most proposals is decoherence: random and uncontrollable loss of quantum information to the computer's environment. Here we consider one promising implementation for quantum computation using the Rydberg blockade mechanism, which stores qubits in optically trapped …
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Coherent control of quantum information
… incoherence can be difficult to separate from decoherence. By studying the fidelity decay under the cyclic entangling map, the effects of incoherence are easily distinguished from decoherence in experimental data. Decoherence free subspaces (DFSs) provide some of the most efficient schemes of …
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Spingineering : quantum control in the presence of relaxation
… with an external environment, it undergoes decoherence - the loss of quantum correlation - and relaxation - the loss of energy - and eventually all of the quantum information is lost. Here we show a general principle of using unitary operators to suppress relaxation processes. Unitary …
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Second order error correction in quantum computing
… codes can prevent the lost of information from decoherence caused by external perturbations. This thesis evaluates a five qubit code for correcting second order bit-flip errors. The code consists of encoding, decoherence, decoding, and error correction steps. This work analyzes the proposed code …
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Quantum-coherent transport in low-dimensional mesoscopic structures and thin films
… mechanisms that give rise to quantum phase decoherence in lithographically patterned mesoscopic structures, of importance in the field of quantum technologies and spintronics. Various mesoscopic structures, namely quantum stadia, quantum wires, and side-gated rings, were fabricated to …
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