Biomedical subjects

D Porras

Publications and source records attributed to D Porras.

6 recordsLinked to original sources

PubMed2006

Quantum manipulation of trapped ions in two dimensional coulomb crystals.

We show that a large number of ions forming a 2D Coulomb crystal provides an almost ideal system for scalable quantum computation and quantum simulation. In particular, the coupling of the internal states to the motion of the ions transverse to the crystal plane allows one to implement two-qubit quantum gates. We analyze in detail the decoherence induced by anharmonic couplings, and show that very high gate fidelities can be achieved with current experimental setups.

Journal Article↗

PubMed2004

Bose-Einstein condensation and strong-correlation behavior of phonons in ion traps.

We show that the dynamics of phonons in a set of trapped ions interacting with lasers is described by a Bose-Hubbard model whose parameters can be externally adjusted. We investigate the possibility of observing several quantum many-body phenomena, including Bose-Einstein condensation as well as a superfluid-Mott insulator quantum phase transition.

Journal Article↗

PubMed2004

Density matrix renormalization group and periodic boundary conditions: a quantum information perspective.

We introduce a picture to analyze the density matrix renormalization group (DMRG) numerical method from a quantum information perspective. This leads to a variational formulation of DMRG which allows for dramatic improvements in the case of problems with periodic boundary conditions. The picture also explains some features of the method in terms of entanglement and teleportation.

Journal Article↗

PubMed2004

Effective quantum spin systems with trapped ions.

We show that the physical system consisting of trapped ions interacting with lasers may undergo a rich variety of quantum phase transitions. By changing the laser intensities and polarizations the dynamics of the internal states of the ions can be controlled, in such a way that an Ising or Heisenberg-like interaction is induced between effective spins. Our scheme allows us to build an analogue quantum simulator of spin systems with trapped ions, and observe and analyze quantum phase transitions with unprecedented opportunities for the measurement and manipulation of spins.

Journal Article↗

PubMed2003

Superoinferior ventricles with superior left ventricle and inferior right ventricle: a newly recognized form of congenital heart disease.

We report the first known case of supero-inferior ventricles with a superior morphologically left ventricle and an inferior morphologically right ventricle. This 2 1/2-year-old boy also had dextrocardia, double-outlet right ventricle [S,L,L], right-sided mitral atresia, left-sided tricuspid regurgitation, a large conoventricular type of ventricular septal defect, and pulmonary outflow tract stenosis. This very rare form of superoinferior ventricles appears to be due to excessive levorotation (approximately equal to 170 degrees) of discordant L-loop ventricles.

Child, Preschool↗

PubMed2000

Distributed computing for membrane-based modeling of action potential propagation.

Action potential propagation simulations with physiologic membrane currents and macroscopic tissue dimensions are computationally expensive. We, therefore, analyzed distributed computing schemes to reduce execution time in workstation clusters by parallelizing solutions with message passing. Four schemes were considered in two-dimensional monodomain simulations with the Beeler-Reuter membrane equations. Parallel speedups measured with each scheme were compared to theoretical speedups, recognizing the relationship between speedup and code portions that executed serially. A data decomposition scheme based on total ionic current provided the best performance. Analysis of communication latencies in that scheme led to a load-balancing algorithm in which measured speedups at 89 +/- 2% and 75 +/- 8% of theoretical speedups were achieved in homogeneous and heterogeneous clusters of workstations. Speedups in this scheme with the Luo-Rudy dynamic membrane equations exceeded 3.0 with eight distributed workstations. Cluster speedups were comparable to those measured during parallel execution on a shared memory machine.

Action Potentials↗