1,598 research outputs found
Compressive mechanical response of graphene foams and their thermal resistance with copper interfaces
We report compressive mechanical response of graphene foams (GFs) and the
thermal resistance () between copper (Cu) and GFs, where GFs were
prepared by the chemical vapor deposition (CVD) method. We observe that Young's
modulus () and compressive strength () of GFs have a power
law dependence on increasing density () of GFs. The maximum
efficiency of absorbed energy () for all GFs during the compression
is larger than ~0.39. We also find that a GF with a higher shows a
larger . In addition, we observe that the measured of
Cu/GFs at room temperature with a contact pressure of 0.25 MP applied increases
from ~50 to ~90 when increases from 4.7 to 31.9
Excitation of atoms in an optical lattice driven by polychromatic amplitude modulation
We investigate the mutiphoton process between different Bloch states in an
amplitude modulated optical lattice. In the experiment, we perform the
modulation with more than one frequency components, which includes a high
degree of freedom and provides a flexible way to coherently control quantum
states. Based on the study of single frequency modulation, we investigate the
collaborative effect of different frequency components in two aspects. Through
double frequency modulations, the spectrums of excitation rates for different
lattice depths are measured. Moreover, interference between two separated
excitation paths is shown, emphasizing the influence of modulation phases when
two modulation frequencies are commensurate. Finally, we demonstrate the
application of the double frequency modulation to design a
large-momentum-transfer beam splitter. The beam splitter is easy in practice
and would not introduce phase shift between two arms.Comment: 11pages, 7 figure
Finite-size analysis of continuous-variable measurement-device-independent quantum key distribution
We study the impact of the finite-size effect on the continuous-variable
measurement-device-independent quantum key distribution (CV-MDI QKD) protocol,
mainly considering the finite-size effect on the parameter estimation
procedure. The central-limit theorem and maximum likelihood estimation theorem
are used to estimate the parameters. We also analyze the relationship between
the number of exchanged signals and the optimal modulation variance in the
protocol. It is proved that when Charlie's position is close to Bob, the CV-MDI
QKD protocol has the farthest transmission distance in the finite-size
scenario. Finally, we discuss the impact of finite-size effects related to the
practical detection in the CV-MDI QKD protocol. The overall results indicate
that the finite-size effect has a great influence on the secret key rate of the
CV-MDI QKD protocol and should not be ignored.Comment: 9 pages, 9 figure
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