297,002 research outputs found
Rydberg state mediated quantum gates and entanglement of pairs of neutral atoms
Experiments performed within the last year have demonstrated Rydberg state
mediated quantum gates and deterministic entanglement between pairs of trapped
neutral atoms. These experiments validate ten year old proposals for Rydberg
mediated quantum logic, but are only the beginning of ongoing efforts to
improve the fidelity of the results obtained and scale the experiments to
larger numbers of qubits. We present here a summary of the results to date,
along with a critical evaluation of the prospects for higher fidelity Rydberg
gates.Comment: submitted to ICAP 2010 proceeding
Competing Ordered States in Bilayer Graphene
We use a perturbative renormalization group approach with short-range
continuum model interactions to analyze the competition between isotropic
gapped and anisotropic gapless ordered states in bilayer graphene, commenting
specifically on the role of exchange and on the importance of spin and valley
flavor degeneracy. By comparing the divergences of the corresponding
susceptibilities, we conclude that this approach predicts gapped states for
flavor numbers N=1,2,4. We also comment briefly on the related gapped states
expected in chiral (ABC) trilayer graphene.Comment: 12 pages, 7 figures and 1 tabl
Algebraic time-decay for the bipolar quantum hydrodynamic model
The initial value problem is considered in the present paper for bipolar
quantum hydrodynamic model for semiconductors (QHD) in . We prove
that the unique strong solution exists globally in time and tends to the
asymptotical state with an algebraic rate as . And, we show that
the global solution of linearized bipolar QHD system decays in time at an
algebraic decay rate from both above and below. This means in general, we can
not get exponential time-decay rate for bipolar QHD system, which is different
from the case of unipolar QHD model (where global solutions tend to the
equilibrium state at an exponential time-decay rate) and is mainly caused by
the nonlinear coupling and cancelation between two carriers. Moreover, it is
also shown that the nonlinear dispersion does not affect the long time
asymptotic behavior, which by product gives rise to the algebraic time-decay
rate of the solution of the bipolar hydrodynamical model in the semiclassical
limit.Comment: 23 page
Deterministic entanglement of two neutral atoms via Rydberg blockade
We demonstrate the first deterministic entanglement of two individually
addressed neutral atoms using a Rydberg blockade mediated controlled-NOT gate.
Parity oscillation measurements reveal an entanglement fidelity of
, which is above the entanglement threshold of , without
any correction for atom loss, and after correcting for
background collisional losses. The fidelity results are shown to be in good
agreement with a detailed error model.Comment: 4 figure
A fundamental limit to the efficiency of spin-exchange optical pumping of 3He nuclei
We establish the existence of a fundamental limit to the efficiency of
spin-exchange optical pumping of 3He nuclei by collisions with spin-polarized
alkali-metal atoms. Using accurate ab initio calculations of molecular
interactions and scattering properties, we show that the maximum 3He spin
polarization that can be achieved in spin-exchange collisions with potassium
(39K) and silver (107Ag) atoms is limited by the anisotropic hyperfine
interaction. We find that spin exchange in Ag-He collisions occurs much faster
than in K-He collisions, suggesting the possibility of using Ag in
spin-exchange optical pumping experiments to increase the production rate of
hyperpolarized 3He. Our analysis indicates that measurements of trap loss rates
of 2S atoms in the presence of cold 3He gas may be used to probe anisotropic
spin-exchange interactions in atom-He collisions.Comment: 5 pages, 4 figure
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