1,404 research outputs found
Effects of multiple pairs on visibility measurements of entangled photons generated by spontaneous parametric processes
Entangled photon-pair sources based on spontaneous parametric processes are
widely used in photonic quantum information experiments. In this paper, we
clarify the relationship between average photon-pair number and the visibility
of two-photon interference (TPI) using those entanglement sources. We consider
sources that generate distinguishable and indistinguishable entangled photon
pairs, assuming coincidence measurements that use threshold detectors. We
present formulas for the TPI visibility of a polarization entanglement that
take account of all the high-order multi-pair emission events. Moreover, we
show that the formulas can be approximated with simple functions of the average
pair number when the photon collection efficiency is small. As a result, we
reveal that an indistinguishable entangled pair provides better visibility than
a distinguishable one
Evolutionary prisoner's dilemma games on the network with punishment and opportunistic partner switching
Punishment and partner switching are two well-studied mechanisms that support
the evolution of cooperation. Observation of human behaviour suggests that the
extent to which punishment is adopted depends on the usage of alternative
mechanisms, including partner switching. In this study, we investigate the
combined effect of punishment and partner switching in evolutionary prisoner's
dilemma games conducted on a network. In the model, agents are located on the
network and participate in the prisoner's dilemma games with punishment. In
addition, they can opportunistically switch interaction partners to improve
their payoff. Our Monte Carlo simulation showed that a large frequency of
punishers is required to suppress defectors when the frequency of partner
switching is low. In contrast, cooperation is the most abundant strategy when
the frequency of partner switching is high regardless of the strength of
punishment. Interestingly, cooperators become abundant not because they avoid
the cost of inflicting punishment and earn a larger average payoff per game but
rather because they have more numerous opportunities to be referred as a role
agent by defectors. Our results imply that the fluidity of social relationships
has a profound effect on the adopted strategy in maintaining cooperation.Comment: 10 pages, 1 table, 8 figures; Figs 6 and 7 are appended to reflect
reviewers' suggestions. Accepted for publication in EPL (Europhysics Letters
ADHM Construction of (Anti-)Self-dual Instantons in Dimensions
The ADHM construction is a very strong scheme to construct the instantons in
four dimensions. We study an ADHM construction of instantons in
dimensions by generalizing this scheme. The higher-dimensional ADHM
construction generates the -dimensional (anti-)self-dual instantons which
satisfy the (anti-)self-dual equation in dimensions:
. Here is the th wedge products of the gauge
field strength 2-form . We also show that our scheme reproduces the known
-dimensional one-instantons and there are multi-instanton solutions of the
't Hooft type in the dilute instanton gas limit. Moreover we discuss a
Harrington-Shepard type caloron in dimensions and this monopole limit.Comment: 23 pages, published versio
Long-distance distribution of time-bin entanglement generated in a cooled fiber
This paper reports the first demonstration of the generation and distribution
of entangled photon pairs in the 1.5-um band using spontaneous four-wave mixing
in a cooled fiber. Noise photons induced by spontaneous Raman scattering were
suppressed by cooling a dispersion shifted fiber with liquid nitrogen, which
resulted in a significant improvement in the visibility of two-photon
interference. By using this scheme, time-bin entangled qubits were successfully
distributed over 60 km of optical fiber with a visibility of 76%, which was
obtained without removing accidental coincidences.Comment: 11 pages, 3 figure
Roles of mutation rate and co-existence of multiple strategy updating rules in evolutionary prisoner's dilemma games
The emergence and maintenance of cooperation has attracted intensive
scholarly interest and has been analysed within the framework of evolutionary
game theory. The role of innovation, which introduces novel strategies into the
population, is a relatively understudied aspect of evolutionary game theory.
Here, we investigate the effects of two sources of innovation---mutation and
heterogeneous updating rules. These mechanisms allow agents to adopt strategies
that do not rely on the imitation of other individuals. The model
introduces---in addition to canonical imitation-based strategy
updating---aspiration-based updating, whereby agents switch their strategy by
referring solely to the performance of their own strategy; mutation also
introduces novel strategies into the population. Our simulation results show
that the introduction of aspiration-based rules into a population of imitators
leads to the deterioration of cooperation. In addition, mutation, in
combination with heterogeneous updating rules, also diminishes cooperators.
This phenomenon is prominent when a large proportion of the population consists
of imitators rather than adopters of aspiration-based updating. Nevertheless, a
high mutation rate, in combination with a low aspiration level, has positive
nonlinear effects, and a heterogeneous population achieves a higher level of
cooperation than the weighted average of homogeneous populations. Our results
demonstrate the profound role of innovation in the evolution of cooperation.Comment: 7 pages, 8 figures, Figs 3(b) and 8 were added following the
reviewers' comment
Two extensions of exact non-equilibrium steady states of a boundary driven cellular automaton
Recently Prosen and Mej\'ia-Monasterio (J. Phys. A: Math. Theor. 49 (2016)
185003) obtained exact nonequilibrium steady states of an integrable and
reversible cellular automaton driven by some stochastic boundary conditions. In
this paper, we explore the possible extensions of their method by generalizing
the boundary conditions. As the result, we find two cases where such an
extension is possible. One is the case where a special condition is satisfied
in a generalized boundary condition. The other is obtained by considering a
conserved quantity as energy and boundaries as heat reservoirs. The latter
includes the original solution as the special case. Properties of the both
solutions are discussed.Comment: 27 pages, 13 figure
Generation of 1.5-um band time-bin entanglement using spontaneous fiber four-wave mixing and planar lightwave circuit interferometers
This paper reports 1.5-um band time-bin entanglement generation. We employed
a spontaneous four-wave mixing process in a dispersion shifted fiber, with
which correlated photon pairs with very narrow bandwidths were generated
efficiently. To observe two-photon interference, we used planar lightwave
circuit based interferometers that were operated stably without feedback
control. As a result, we obtained coincidence fringes with 99 % visibilities
after subtracting accidental coincidences, and successfully distributed
entangled photons over 20-km standard single-mode fiber without any
deterioration in the quantum correlation.Comment: 4 pages, 3 figure
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