nt - p h / 04 02 17 6 v 2 1 F eb 2 00 5 Loss of quantum coherence in a system coupled to a zero - temperature environment

ar X iv : q ua nt - p h / 04 02 02 8 v 2 7 F eb 2 00 5 External Time - Varying Fields and Electron Coherence

The effect of time-varying electromagnetic fields on electron coherence is investigated. A sinusoidal electromagnetic field produces a time varying Aharonov-Bohm phase. In a measurement of the interference pattern which averages over this phase, the effect is a loss of contrast. This is effectively a form of decoherence. We calculate the magnitude of this effect for various electromagnetic fiel...

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...

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...

nt - p h / 03 02 02 8 v 1 4 F eb 2 00 3 Quantum Tomography

ua nt - p h / 02 02 03 0 v 1 5 F eb 2 00 2 Quantum Computer with Fixed Interaction is Universal

It is proved that a quantum computer with fixed and permanent interaction of diagonal type between qubits proposed in the work quant-ph/0201132 is universal. Such computer is controlled only by one-qubit quick transformations, and this makes it feasible.