ar X iv : q ua nt - p h / 04 05 01 1 v 1 3 M ay 2 00 4 Decoherence alias Loschmidt echo of the environment

ar X iv : q ua nt - p h / 05 05 05 6 v 1 9 M ay 2 00 5 Decoherence at absolute zero

We present an analytical study of the loss of quantum coherence at absolute zero. Our model consists of a harmonic oscillator coupled to an environment of harmonic oscillators at absolute zero. We find that for an Ohmic bath, the offdiagonal elements of the density matrix in the position representation decay as a power law in time at late times. This slow loss of coherence in the quantum domain...

ar X iv : q ua nt - p h / 04 05 11 6 v 1 2 0 M ay 2 00 4 Complementarity of Entanglement and Interference

A complementarity relation is shown between the visibility of interference and bipartite entanglement in a two qubit interferometric system when the parameters of the quantum operation change for a given input state. The entanglement measure is a decreasing function of the visibility of interference. The implications for quantum computation are briefly discussed.

ar X iv : q ua nt - p h / 04 11 17 2 v 1 2 3 N ov 2 00 4 Information and Entropy in Quantum Theory

ar X iv : q ua nt - p h / 04 06 00 1 v 1 3 1 M ay 2 00 4 Decoherence by a chaotic many - spin bath

We numerically investigate decoherence of a two-spin system (central system) by a bath of many spins 1/2. By carefully adjusting parameters, the dynamical regime of the bath has been varied from quantum chaos to regular, while all other dynamical characteristics have been kept practically intact. We explicitly demonstrate that for a many-body quantum bath, the onset of quantum chaos leads to si...

ar X iv : q ua nt - p h / 06 05 10 3 v 1 1 1 M ay 2 00 6 On Concurrence and Entanglement of Rank Two Channels ∗ Armin Uhlmann

Concurrence and further entanglement quantifiers can be computed explicitly for channels of rank two if representable by just two Kraus operators. Almost all details are available for the subclass of rank two 1-qubit channels. There is a simple geometric picture beyond, explaining nicely the role of anti-linearity.