nt - p h / 05 09 00 1 v 1 1 Se p 20 05 Locally observable conditions for the successful implementation of entangling multi - qubit quantum gates

ua nt - p h / 06 05 18 5 v 3 3 1 Ja n 20 09 Single qubit , two qubit gates and no signalling principle

In this work we investigate that whether one can construct single and two qubit gates for arbitrary quantum states from the principle of no signalling. We considered the problem for Pauli gates, Hadamard gate, C-Not gate.

ua nt - p h / 05 09 21 8 v 1 3 0 Se p 20 05 N - qubit entanglement via the J 2 y - type collective interaction

ar X iv : q ua nt - p h / 05 09 08 5 v 1 1 3 Se p 20 05 Improving the purity of one - and two - qubit gates by AC fields

We investigate the influence of AC driving fields on the coherence properties of one-and two-qubit gate operations. In both cases, we find that for suitable driving parameters, the gate purity improves significantly. A mapping of the time-dependent system-bath model to an effective static model provides analytical results. The resulting purity loss compares favorably with numerical results.

ua nt - p h / 06 03 05 9 v 1 7 M ar 2 00 6 Entanglement Distribution and Entangling Power of Quantum Gates

Quantum gates, that play a fundamental role in quantum computation and other quantum information processes, are unitary evolution operatorsˆU that act on a composite system changing its entanglement. In the present contribution we study some aspects of these entanglement changes. By recourse of a Monte Carlo procedure, we compute the so called " entangling power " for several paradigmatic quant...

nt - p h / 05 06 04 3 v 1 6 J un 2 00 5 Segre variety , conifold , Hopf fibration , and separable multi - qubit states

We establish relations between Segre variety, conifold, Hopf fibration, and separable sets of pure two-qubit states. Moreover, we investigate the geometry and topology of separable sets of pure multi-qubit states based on a complex multi-projective Segre variety and higher order Hopf fibration.