arXiv subjects

D. Ahrensmeier

Publications and source records attributed to D. Ahrensmeier.

4 recordsLinked to original sources

arXiv2006

The Dynamics of Entanglement in the Adiabatic Search and Deutsch Algorithms

The goal of this paper is to study the effect of entanglement on the running time of a quantum computation. Adiabatic quantum computation is suited to this kind of study, since it allows us to explicitly calculate the time evolution of the entanglement throughout the calculation. On the other hand however, the adiabatic formalism makes it impossible to study the roles of entanglement and fidelity separately, which means that results have to be interpreted carefully. We study two algorithms: the search algorithm and the Deutsch-Jozsa algorithm. We find some evidence that entanglement can be considered a resource in quantum computation.

quant-ph↗

arXiv2002

Far-from-equilibrium dynamics with broken symmetries from the 2PI-1/N expansion

We derive the nonequilibrium real-time evolution of an O(N) - invariant scalar quantum field theory in the presence of a nonvanishing expectation value of the quantum field. Using a systematic 1/N expansion of the 2PI effective action to next-to-leading order, we obtain nonperturbative evolution equations which include scattering and memory effects. The equivalence of the direct method, which requires the resummation of an infinite number of skeleton diagrams, with the auxiliary-field formalism, which involves only one diagram at next-to-leading order, is shown.

hep-ph↗

arXiv2001

Parametric amplification versus collisions: An illustrative application

We investigate the time dependence of the quantum statistical model with $λϕ^4/4!$ self-interaction and consider the resulting induced particle number density. For a special example in which the classical approximation exhibits parametric resonance, the effects of the back reaction and especially of collisions, treated in a perturbative way, are analysed.

hep-ph↗

arXiv2000

Resonant decay of parity odd bubbles in hot hadronic matter

We investigate the decay of metastable states with broken CP-symmetry which have recently been proposed by Kharzeev, Pisarski and Tytgat to form in hot hadronic matter. We consider the efficiency of the amplification of the $η'$-field via parametric resonance, taking the backreaction into account. For times of the order $t\approx 10 fm$, we find a particle density of about $0.7/fm^3$ and a correlation length of $ξ_{max}\approx 2.5 fm$. The corresponding momentum spectra show a non-thermal behaviour.

hep-ph↗