10,097 research outputs found
Can the Lepton Flavor Mixing Matrix Be Symmetric?
Current neutrino oscillation data indicate that the 3x3 lepton flavor mixing
matrix V is likely to be symmetric about its V_{e3}-V_{\mu 2}-V_{\tau 1} axis.
This off-diagonal symmetry corresponds to three pairs of {\it congruent}
unitarity triangles in the complex plane. Terrestrial matter effects can
substantially modify the genuine CP-violating parameter and off-diagonal
asymmetries of V in realistic long-baseline experiments of neutrino
oscillations.Comment: RexTex 14 pages (4 PS figures). More discussions adde
Probing spin entanglement by gate-voltage-controlled interference of current correlation in quantum spin Hall insulators
We propose an entanglement detector composed of two quantum spin Hall
insulators and a side gate deposited on one of the edge channels. For an ac
gate voltage, the differential noise contributed from the entangled electron
pairs exhibits the nontrivial step structures, from which the spin entanglement
concurrence can be easily obtained. The possible spin dephasing effects in the
quantum spin Hall insulators are also included.Comment: Physics Letters A in pres
More Straightforward Extraction of the Fundamental Lepton Mixing Parameters from Long-Baseline Neutrino Oscillations
We point out the simple reversibility between the fundamental neutrino mixing
parameters in vacuum and their effective counterparts in matter. The former can
therefore be expressed in terms of the latter, allowing more straightforward
extraction of the genuine lepton mixing quantities from a variety of
long-baseline neutrino oscillation experiments. In addition to the
parametrization-independent results, we present the formulas based on the
standard parametrization of the lepton flavor mixing matrix and give a typical
numerical illustration.Comment: RevTex 10 pages. Minor changes. Phys. Rev. D in printin
Universal conductance fluctuation of mesoscopic systems in the metal-insulator crossover regime
We report a theoretical investigation on conductance fluctuation of mesoscopic systems. Extensive numerical simulations on quasi-one-dimensional, two-dimensional, and quantum dot systems with different symmetriescircular orthogonal ensemble, circular unitary ensemble (CUE), and 〔circular symplectic ensemble (CSE)〕indicate that the conductance fluctuation can reach a universal value in the crossover regime for systems with CUE and CSE symmetries. The conductance distribution is found to be a universal function from diffusive to localized regimes that depends only on the average conductance, dimensionality, and symmetry of the system. The numerical solution of DMPK equation agrees with our result in quasi-one dimension. Our numerical results in two dimensions suggest that this universal conductance fluctuation is related to the metal-insulator transition. In the localized regime with average conductance <0.3, the conductance distribution seems to be superuniversal independent of dimensionality and symmetry.published_or_final_versio
Quantum computing through electron propagation in the edge states of quantum spin Hall systems
We propose to implement quantum computing based on electronic spin qubits by
controlling the propagation of the electron wave packets through the helical
edge states of quantum spin Hall systems (QSHs). Specfically, two
non-commutative single-qubit gates, which rotate a qubit around z and y axes,
can be realized by utilizing gate voltages either on a single QSH edge channel
or on a quantum point contact structure. The more challenging two-qubit
controlled phase gate can be implemented through the on-demand capacitive
Coulomb interaction between two adjacent edge channels from two parallel QSHs.
As a result, a universal set of quantum gates can be achieved in an
all-electrical way. The fidelity and purity of the two-qubit gate are
calculated with both time delay and finite width of the wave packets taken into
consideration, which can reach high values with the existing high-quality
single electron source
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