A method to find quantum noiseless subsystems

We develop a structure theory for decoherence-free subspaces and noiseless subsystems that applies to arbitrary (not necessarily unital) quantum operations. The theory can be alternatively phrased in terms of the superoperator perspective, or the algebraic noise commutant formalism. As an application, we propose a method for finding all such subspaces and subsystems for arbitrary quantum operations. We suggest that this work brings the fundamental passive technique for error correction in quantum computing an important step closer to practical realization.Comment: 5 pages, to appear in Physical Review Letter

Corrections to Gravity due to a Sol Manifold Extra Dimensional Space

The corrections to the gravitational potential due to a Sol extra dimensional compact manifold, denoted as $M_A^3$, are studied. The total spacetime is of the form $M^4\times M_A^3$. The range of the Sol corrections is investigated and compared to the range of the $T^3$ corrections.Comment: 13 pages, 10 figures, published versio

Black hole evaporation with separated fermions

In models with a low quantum gravity scale, a well-motivated reason to expect quark and lepton fields are localized but physically separated is to avoid proton decay. This could happen in a ``fat-brane'' or in an additional, orthogonal 1/TeV sized dimension in which the gauge and Higgs fields live throughout. Black holes with masses of order the quantum gravity scale are therefore expected to evaporate non-universally, preferentially radiating directly into quarks or leptons but not both. Should black holes be copiously produced at a future hadron collider, we find the ratio of final state jets to charged leptons to photons is 113:8:1, which differs from previous analyses that assumed all standard model fields live at the same point in the extra dimensional space.Comment: 5 pages, REVTe

Heavy Charged Gauge Bosons with General CP Violating Couplings

Heavy gauge bosons such as $W^{\prime}$ are expected to exist in many extensions of the Standard Model. In this paper, it is shown that the most general Lagrangian for the interaction of $W^{\prime}$ with top and bottom quarks which consists of V-A and V+A structure with in general complex couplings produces an Electric Dipole Moment (EDM) for the top quark at one loop level. We predict the allowed ranges for the mass and couplings of $W^{\prime}$ by using the upper limit on the top quark EDM

Inelastic Dark Matter in Light of DAMA/LIBRA

Inelastic dark matter, in which WIMP-nucleus scatterings occur through a transition to an excited WIMP state ~ 100 keV above the ground state, provides a compelling explanation of the DAMA annual modulation signal. We demonstrate that the relative sensitivities of various dark matter direct detection experiments are modified such that the DAMA annual modulation signal can be reconciled with the absence of a reported signal at CDMS-Soudan, XENON10, ZEPLIN, CRESST, and KIMS for inelastic WIMPs with masses O(100 GeV). We review the status of these experiments, and make predictions for upcoming ones. In particular, we note that inelastic dark matter leads to highly suppressed signals at low energy, with most events typically occurring between 20 to 45 keV (unquenched) at xenon and iodine experiments, and generally no events at low (~ 10 keV) energies. Suppressing the background in this high energy region is essential to testing this scenario. The recent CRESST data suggest seven observed tungsten events, which is consistent with expectations from this model. If the tungsten signal persists at future CRESST runs, it would provide compelling evidence for inelastic dark matter, while its absence should exclude it.Comment: 27 pages, 17 figures, minor revision