Numerical Evidence for Robustness of Environment-Assisted Quantum Transport

Recent theoretical studies show that decoherence process can enhance transport efficiency in quantum systems. This effect is known as environment-assisted quantum transport (ENAQT). The role of ENAQT in optimal quantum transport is well investigated, however, it is less known how robust ENAQT is with respect to variations in the system or its environment characteristic. Toward answering this question, we simulated excitonic energy transfer in Fenna-Matthews-Olson (FMO) photosynthetic complex. We found that ENAQT is robust with respect to many relevant parameters of environmental interactions and Frenkel-exciton Hamiltonian including reorganization energy, bath frequency cutoff, temperature, and initial excitations, dissipation rate, trapping rate, disorders, and dipole moments orientations. Our study suggests that the ENAQT phenomenon can be exploited in robust design of highly efficient quantum transport systems.Comment: arXiv admin note: substantial text overlap with arXiv:1104.481

Vanishing quantum discord is necessary and sufficient for completely positive maps

Two long standing open problems in quantum theory are to characterize the class of initial system-bath states for which quantum dynamics is equivalent to (1) a map between the initial and final system states, and (2) a completely positive (CP) map. The CP map problem is especially important, due to the widespread use of such maps in quantum information processing and open quantum systems theory. Here we settle both these questions by showing that the answer to the first is "all", with the resulting map being Hermitian, and that the answer to the second is that CP maps arise exclusively from the class of separable states with vanishing quantum discord.Comment: 4 pages, no figures. v2: Accepted for publication in Phys. Rev. Let

Relation between parvovirus B19 infection and fetal mortality and spontaneous abortion

Background: Infection with parvovirus B19 may cause fetal losses including spontaneous abortion, intrauterine fetal death and non-immune hydrops fetalis. The aim of this study is to determine the frequency of parvovirus B19 in formalin fixed placental tissues in lost fetuses using real-time PCR method. Methods: In this cross-sectional study, 100 formalin fixed placental tissues with unknown cause of fetal death were determined using real-time PCR method after DNA extraction. Results: Six out of 100 cases (6) were positive for parvovirus B19 using real-time PCR. Gestational age of all positive cases was less than 20 weeks with a mean of 12.3 weeks. Three cases have a history of abortion and all of positive cases were collected in spring. Mean age of positive cases were 28 years. Conclusion: Parvovirus B19 during pregnancy can infect red precursor cells and induces apoptosis or lyses these cells that resulting in anemia and congestive heart failure leading to fetal death. Management of parvovirus B19 infection in pregnant women is important because immediate diagnosis and transfusion in hydropsic fetuses can decrease the risk of fetal death

Locally Optimal Control of Quantum Systems with Strong Feedback

For quantum systems with high purity, we find all observables that, when continuously monitored, maximize the instantaneous reduction in the von Neumann entropy. This allows us to obtain all locally optimal feedback protocols with strong feedback, and explicit expressions for the best such protocols for systems of size N <= 4. We also show that for a qutrit the locally optimal protocol is the optimal protocol for a given range of control times, and derive an upper bound on all optimal protocols with strong feedback.Comment: 4 pages, Revtex4. v2: published version (some errors corrected

The galaxy rotation curves in the f(R,T)f(R,T) modified gravity formalism

Astronomical data have shown that the galaxy rotation curves are mostly flat in the far distance of the galactic cores, which reveals the insufficiency of our knowledges about how gravity works in these regimes. In this paper we introduce a resolution of this issue from the $f(R,T)$ modified gravity formalism perspective. By investigating two classes of models with separable (minimal coupling model) and inseparable (non-minimal coupling model) parts of the Ricci scalar $R$ and trace of the energy-momentum tensor $T$, we find that only in the latter models it is possible to attain flat galaxy rotation curves.Comment: 9 pages, 4 figure