21 research outputs found
Evolutionarily Stable Strategies in Quantum Games
Evolutionarily Stable Strategy (ESS) in classical game theory is a refinement
of Nash equilibrium concept. We investigate the consequences when a small group
of mutants using quantum strategies try to invade a classical ESS in a
population engaged in symmetric bimatrix game of Prisoner's Dilemma. Secondly
we show that in an asymmetric quantum game between two players an ESS pair can
be made to appear or disappear by resorting to entangled or unentangled initial
states used to play the game even when the strategy pair remains a Nash
equilibrium in both forms of the game.Comment: RevTex,contents extended to include asymmetric games,no figur
Background-free detection of trapped ions
We demonstrate a Doppler cooling and detection scheme for ions with low-lying
D levels which almost entirely suppresses scattered laser light background,
while retaining a high fluorescence signal and efficient cooling. We cool a
single ion with a laser on the 2S1/2 to 2P1/2 transition as usual, but repump
via the 2P3/2 level. By filtering out light on the cooling transition and
detecting only the fluorescence from the 2P_3/2 to 2S1/2 decays, we suppress
the scattered laser light background count rate to 1 per second while
maintaining a signal of 29000 per second with moderate saturation of the
cooling transition. This scheme will be particularly useful for experiments
where ions are trapped in close proximity to surfaces, such as the trap
electrodes in microfabricated ion traps, which leads to high background scatter
from the cooling beam
Designing spin-spin interactions with one and two dimensional ion crystals in planar micro traps
We discuss the experimental feasibility of quantum simulation with trapped
ion crystals, using magnetic field gradients. We describe a micro structured
planar ion trap, which contains a central wire loop generating a strong
magnetic gradient of about 20 T/m in an ion crystal held about 160 \mu m above
the surface. On the theoretical side, we extend a proposal about spin-spin
interactions via magnetic gradient induced coupling (MAGIC) [Johanning, et al,
J. Phys. B: At. Mol. Opt. Phys. 42 (2009) 154009]. We describe aspects where
planar ion traps promise novel physics: Spin-spin coupling strengths of
transversal eigenmodes exhibit significant advantages over the coupling schemes
in longitudinal direction that have been previously investigated. With a chip
device and a magnetic field coil with small inductance, a resonant enhancement
of magnetic spin forces through the application of alternating magnetic field
gradients is proposed. Such resonantly enhanced spin-spin coupling may be used,
for instance, to create Schr\"odinger cat states. Finally we investigate
magnetic gradient interactions in two-dimensional ion crystals, and discuss
frustration effects in such two-dimensional arrangements.Comment: 20 pages, 13 figure
Integration of fluorescence collection optics with a microfabricated surface electrode ion trap
We have successfully demonstrated an integrated optical system for collecting
the fluorescence from a trapped ion. The system, consisting of an array of
transmissive, dielectric micro-optics and an optical fiber array, has been
intimately incorporated into the ion-trapping chip without negatively impacting
trapping performance. Epoxies, vacuum feedthrough, and optical component
materials were carefully chosen so that they did not degrade the vacuum
environment, and we have demonstrated light detection as well as ion trapping
and shuttling behavior comparable to trapping chips without integrated optics,
with no modification to the control voltages of the trapping chip.Comment: 14 pages, 12 figure
Equilibrium tracing in strategic-form games
Bimatrix game, Equilibrium computation, Homotopy methods, Index, C72,