1,086 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
Antenna pattern modification for single reflector antennas
The problem of correcting the antenna temperatures observed with a single reflector is addressed from two viewpoints with emphasis on decreasing the level of the side lobes without greatly amplifying the noise. One viewpoint is that of matrix operations where the elements of the matrix are integrals of the antenna pattern. This formulation is directly applicable to developing algorithms. The other is that of an analysis of the problem by treating the antenna as a spatial filter and using Fourier transforms of the antenna pattern. This approach leads to an understanding of the problem, but is not suitable for performing calculations. The method developed can be used to correct data from mechanically-scanned microwave instruments that view Earth from space
Quantum logic gates using Stark shifted Raman transitions in a cavity
We present a scheme to realise the basic two-quibit logic gates such as
quantum phase gate and controlle-NOT gate using a detuned optical cavity
interacting with a three-level Raman system. We discuss the role of Stark
shifts which are as important as the terms leading to two-photon transition.
The operation of the proposed logic gates involves metastable states of the
atom and hence is not affected by spontaneous emission. These ideas can be
extended to produce multiparticle entanglement.Comment: 5 pages, 1 figure, RevTeX4, Text is modifie
On the mean width of log-concave functions
In this work we present a new, natural, definition for the mean width of
log-concave functions. We show that the new definition coincide with a previous
one by B. Klartag and V. Milman, and deduce some properties of the mean width,
including an Urysohn type inequality. Finally, we prove a functional version of
the finite volume ratio estimate and the low-M* estimate.Comment: 15 page
- …