Search results for "Quantum dissipation"
showing 10 items of 40 documents
Unavoidable decoherence in semiconductor quantum dots
2005
Phonon-induced unavoidable decoherence of orbital degrees of freedom in quantum dots is studied and the relevant time scales are estimated. Dephasing of excitons due to acoustic phonons and, in a polar medium, to optical phonons, including anharmonic effects and enhancement of the effective Fr\"ohlich constant due to localization, is assessed for typical self-assembled quantum dots. Temporal inefficiency of Pauli blocking due to lattice inertia is predicted. For quantum dots placed in a diluted magnetic semiconductor medium a magnon-induced dephasing of a spin is also estimated in accordance with experimental results.
Wave Packet Decoherence in Momentum Space
2004
We consider the development of decoherence between the momentum components of a wave packet of a non relativistic charged particle interacting linearly with the electromagnetic field in equilibrium at temperature T. By adopting from the beginning the electric dipole approximation the Hamiltonian assumes a form analogous to the one used in the context of quantum computing for an ensemble of two level systems. We obtain the characteristic vacuum and thermal decoherence times and we show that decoherence between different momenta is due to the onset of a correlation between each momentum component and the associated transverse photons that are also responsible of mass renormalization.
Observation of time-invariant coherence in a nuclear magnetic resonance quantum simulator
2016
The ability to live in coherent superpositions is a signature trait of quantum systems and constitutes an irreplaceable resource for quantum-enhanced technologies. However, decoherence effects usually destroy quantum superpositions. It was recently predicted that, in a composite quantum system exposed to dephasing noise, quantum coherence in a transversal reference basis can stay protected for an indefinite time. This can occur for a class of quantum states independently of the measure used to quantify coherence, and it requires no control on the system during the dynamics. Here, such an invariant coherence phenomenon is observed experimentally in two different setups based on nuclear magne…
The role of environmental correlations in the non-Markovian dynamics of a spin system
2011
We put forward a framework to study the dynamics of a chain of interacting quantum particles affected by individual or collective multi-mode environment, focussing on the role played by the environmental quantum correlations over the evolution of the chain. The presence of entanglement in the state of the environmental system magnifies the non-Markovian nature of the chain's dynamics, giving rise to structures in figures of merit such as entanglement and purity that are not observed under a separable multi-mode environment. Our analysis can be relevant to problems tackling the open-system dynamics of biological complexes of strong current interest.
Rotating electrons in quantum dots: Classical limit
2007
We solve the problem of a few electrons in a two-dimensional harmonic confinement using a quantum mechanical exact diagonalization technique, on the one hand, and classical mechanics, on the other. The quantitative agreement between the results of these two calculations suggests that, at low filling factors, all the low energy excitations of a quantum Hall liquid are classical vibrations of localized electrons. The Coriolis force plays a dominant role in determining the classical vibration frequencies.
Solitons ofq-deformed quantum lattices and the quantum soliton
2001
We use the classical N-soliton solution of a q-deformed lattice, the Maxwell-Bloch (MB) lattice, which we reported recently (Rybin A V, Varzugin G G, Timonen J and Bullough R K Year 2001 J. Phys. A: Math. Gen. 34 157) in order, ultimately, to fully comprehend the `quantum soliton'. This object may be the source of a new information technology (Abram I 1999 Quantum solitons Phys. World 21-4). We suggested in Rybin et al 2001 that a natural quantum mechanical matrix element of the q-deformed quantum MB lattice becomes in a suitable limit the classical 1-soliton solution of the classical q-deformed MB lattice explicitly derived by a variant of the Darboux-Backlund method. The classical q-defor…
Fast Control of Quantum States in Quantum Dots: Limits due to Decoherence
2005
We study the kinetics of confined carrier-phonon system in a quantum dot under fast optical driving and discuss the resulting limitations to fast coherent control over the quantum state in such systems.
Quantum control theory for decoherence suppression in quantum gates
2007
We show how quantum optimal control theory can help achieve high-fidelity quantum gates in real experimental settings. We discuss several optimization methods (from iterative algorithms to optimization by interference and to impulsive control) and different physical scenarios (from optical lattices to atom chips and to Rydberg atoms).
Space-Time Symmetries in Quantum Physics
2013
The transformations in space and in time which belong to the Galilei group play an important role in quantum theory. In some respect and for some aspects, their role is new as compared to classical mechanics.
Quantum capacitance: a microscopic derivation
2010
We start from microscopic approach to many body physics and show the analytical steps and approximations required to arrive at the concept of quantum capacitance. These approximations are valid only in the semi-classical limit and the quantum capacitance in that case is determined by Lindhard function. The effective capacitance is the geometrical capacitance and the quantum capacitance in series, and this too is established starting from a microscopic theory.