1,610 research outputs found
Vacuum induced Stark shifts for quantum logic using a collective system in a high quality dispersive cavity
A collective system of atoms in a high quality cavity can be described by a
nonlinear interaction which arises due to the Lamb shift of the energy levels
due to the cavity vacuum [Agarwal et al., Phys. Rev. A 56, 2249 (1997)]. We
show how this collective interaction can be used to perform quantum logic. In
particular we produce schemes to realize CNOT gates not only for two-qubit but
also for three-qubit systems. We also discuss realizations of Toffoli gates.
Our effective Hamiltonian is also realized in other systems such as trapped
ions or magnetic molecules
Non-additivity of Renyi entropy and Dvoretzky's Theorem
The goal of this note is to show that the analysis of the minimum output
p-Renyi entropy of a typical quantum channel essentially amounts to applying
Milman's version of Dvoretzky's Theorem about almost Euclidean sections of
high-dimensional convex bodies. This conceptually simplifies the
(nonconstructive) argument by Hayden-Winter disproving the additivity
conjecture for the minimal output p-Renyi entropy (for p>1).Comment: 8 pages, LaTeX; v2: added and updated references, minor editorial
changes, no content change
Molecular orientation entanglement and temporal Bell-type inequalities
We detail and extend the results of [Milman {\it et al.}, Phys. Rev. Lett.
{\bf 99}, 130405 (2007)] on Bell-type inequalities based on correlations
between measurements of continuous observables performed on trapped molecular
systems. We show that for some observables with a continuous spectrum which is
bounded, one is able to construct non-locality tests sharing common properties
with those for two-level systems. The specific observable studied here is
molecular spatial orientation, and it can be experimentally measured for single
molecules, as required in our protocol. We also provide some useful general
properties of the derived inequalities and study their robustness to noise.
Finally, we detail possible experimental scenarii and analyze the role played
by different experimental parameters.Comment: 10 pages and 5 figure
- …