15,484 research outputs found
Landau Ginzburg Theory and Nuclear Matter at Finite Temperature
Based on recent studies of the temperature dependence of the energy and
specific heat of liquid nuclear matter, a phase transition is suggested at a
temperature MeV. We apply Landau Ginzburg theory to this transition
and determine the behaviour of the energy and specific heat close to the
critical temperature in the condensed phase.Comment: 10 pages, Revte
Free induction decay of a superposition stored in a quantum dot
We study the free evolution of a superposition initialized with high fidelity
in the neutral-exciton state of a quantum dot. Readout of the state at later
times is achieved by polarized photon detection, averaged over a large number
of cycles. By controlling the fine-structure splitting (FSS) of the dot with a
dc electric field, we show a reduction in the degree of polarization of the
signal when the splitting is minimized. In analogy with the "free induction
decay" observed in nuclear magnetic resonance, we attribute this to hyperfine
interactions with nuclei in the semiconductor. We numerically model this effect
and find good agreement with experimental studies. Our findings have
implications for storage of superpositions in solid-state systems and for
entangled photon pair emission protocols that require a small value of the FSS
Bell-inequality violation with a triggered photon-pair source
Here we demonstrate, for the first time, violation of Bell's inequality using
a triggered quantum dot photon-pair source without post-selection. Furthermore,
the fidelity to the expected Bell state can be increased above 90% using
temporal gating to reject photons emitted at times when collection of
uncorrelated light is more probable. A direct measurement of a CHSH Bell
inequality is made showing a clear violation, highlighting that a quantum dot
entangled photon source is suitable for communication exploiting non-local
quantum correlations.Comment: 14 pages, 4 figure
Electrometry using the quantum Hall effect in a bilayer 2D electron system
We discuss the development of a sensitive electrometer that utilizes a
two-dimensional electron gas (2DEG) in the quantum Hall regime. As a
demonstration, we measure the evolution of the Landau levels in a second,
nearby 2DEG as the applied perpendicular magnetic field is changed, and extract
an effective mass for electrons in GaAs that agrees within experimental error
with previous measurements.Comment: 3.5 pages, 3 figures, submitted to APL
Origin of the hysteresis in bilayer 2D systems in the quantum Hall regime
The hysteresis observed in the magnetoresistance of bilayer 2D systems in the
quantum Hall regime is generally attributed to the long time constant for
charge transfer between the 2D systems due to the very low conductivity of the
quantum Hall bulk states. We report electrometry measurements of a bilayer 2D
system that demonstrate that the hysteresis is instead due to non-equilibrium
induced current. This finding is consistent with magnetometry and electrometry
measurements of single 2D systems, and has important ramifications for
understanding hysteresis in bilayer 2D systems.Comment: 4 pages, 3 figs. Accepted for publication in PR
Some Empirical Criteria for Attributing Creativity to a Computer Program
Peer reviewedPostprin
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