6,674 research outputs found
Interferometric distillation and determination of unknown two-qubit entanglement
We propose a scheme for both distilling and quantifying entanglement,
applicable to individual copies of an arbitrary unknown two-qubit state. It is
realized in a usual two-qubit interferometry with local filtering. Proper
filtering operation for the maximal distillation of the state is achieved, by
erasing single-qubit interference, and then the concurrence of the state is
determined directly from the visibilities of two-qubit interference. We compare
the scheme with full state tomography
Bilayer Graphene Interferometry : Phase Jump and Wave Collimation
We theoretically study the phase of the reflection amplitude of an electron
(massive Dirac fermion) at a lateral potential step in Bernal-stacked bilayer
graphene. The phase shows anomalous jump of , as the electron incidence
angle (relative to the normal direction to the step) varies to pass . The jump is attributed to the Berry phase associated with the
pseudospin-1/2 of the electron. This Berry-phase effect is robust against the
band gap opening due to the external electric gates generating the step. We
propose an interferometry setup in which collimated waves can be generated and
tuned. By using the setup, one can identify both the jump and the
collimation angle.Comment: 4 pages, 6 figure
Spectator Behavior in a Quantum Hall Antidot with Multiple Bound Modes
We theoretically study Aharonov-Bohm resonances in an antidot system with
multiple bound modes in the integer quantum Hall regime, taking capacitive
interactions between the modes into account. We find the spectator behavior
that the resonances of some modes disappear and instead are replaced by those
of other modes, due to internal charge relaxation between the modes. This
behavior is a possible origin of the features of previous experimental data
which remain unexplained, spectator behavior in an antidot molecule and
resonances in a single antidot with three modes.Comment: 4 pages, 3 figures, to be published in Physical Review Letter
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