Documents / Report
This Defense Intelligence Reference Document from the Defense Intelligence Agency, dated 10 December 2010, is one of a series of advanced technology reports produced in FY 2010 under the Advanced Aerospace Weapon System Applications (AAWSA) Program. It reviews quantum computing technologies and DNA-based molecular computing for onboard supercomputing on future spacecraft. It forecasts ion-trap quantum computers within 10 years, simple DNA tile computing within 20 years, and self-repairing DNA computers on a 40-year horizon.
“The Advance”7 pages
UNCLASSIFIED/ ,'F811. 8FFll!liillt 1!1!11! SHL"i' Graphene Disc in Bilayer Graphene Bilayer graphene is the two-layer analog of the single layer. The two sublattices are coupled by the so-called Bernal stacking. A voltage V between the two layers breaks inversion symmetry (like the mass term b.. in the single layer) and opens a gap proportional to the voltage. In addition, the combination of a top gate and a back gate allows tuning the gap and the average potential U(r) independently. A central issue, from a computational electronics perspective, is to quantitatively study the condensed state. In materials-based device models, one has an underlying Hamiltonian, such as an ab initio Hamiltonian.m In principle, the excitonic condensate emerges from the interacting particles described by the Hamiltonian. It is shown that both true bound states and quasi-bound states occur, depending on the form of the potentials. In addition, there is a third and most interesting possibility where the character of the states depends on the parameters of the potentials and can be controlled at will. A confinement-de-confinement transition then occurs in which the character of the states changes from oscillatory to exponential as in the Klein paradox for particles with mass. This gives a way of probing the Klein paradox experimentally in a solid state system and numerical studies of the quantum states in a realistic dot model show it is feasible. Further, the same effect could be used to fabricate a graphene dot which has true bound states. This only requires a uniform magnetic field and a gate which can be made lithographically, a geometry that is much easier to fabricate than the non-uniform magnetic field geometry. The relativistic nature of the transmission, exactly 100%, does not depend on E and Vo is a consequence of the zero mass. If the particles had mass mo, the energy-momentum relation would be (E - V) 2 - p2c2 = mo2 c4 and the amplitudes of the wave function components in equations of motion would depend on k or k' and mo. Then the right side amplitude in equations would be different from the left side amplitude, so a reflected wave would have to be introduced to satisfy the boundary condition at x = 0 and the transmission coefficient would not be 100%. iilaycr grapliclH' top gntf' (lll dopa11t' ato' ' f '' ' • • +' + • ' • • • ' ' •' ' ' • lllS Si02 hnrk gate, Figure 5. Quantum dot in bilayer graphene. "' Ab initio Hamiltonian is one derived from first principles. 17 UNCLASSIFIED/ /F811. 8Fflliil.l1k Wliili SUI kif
Not linked to a story yet.
Report, from the dia collection. The PDF is mirrored here; the original link is above. 54 pages are in the text index: search them above, or from the library's search.