1,041 research outputs found
"SAMs meet MEMS": surface modification with self-assembled monolayers for the dry-demolding of photoplastic MEMS/NEMS
In this contribution we demonstrate the use of self-assembled monolayers (SAMs) as anti-adhesion coating to assist the removal of photoplastic MEMS/NEMS with a patterned metal layer from the surface without wet chemical sacrificial layer etching, so-called 'dry-demolding'. The SAMs functionality here is to reduce the stiction between the surface and a thin evaporated metal film. The double-layer SAM/metal provides enough stability to support subsequent micromachining step
Conductivity sum rule, implication for in-plane dynamics and c-axis response
Recently observed -axis optical sum rule violations indicate non-Fermi
liquid in-plane behavior. For coherent -axis coupling, the observed flat,
nearly frequency independent -axis conductivity implies
a large in-plane scattering rate around and therefore any
pseudogap that might form at low frequency in the normal state will be smeared.
On the other hand incoherent -axis coupling places no restriction on the
value of and gives a more consistent picture of the observed sum rule
violation which, we find in some cases, can be less than half.Comment: 3 figures. To appear in PR
Interferometric Bell-state preparation using femtosecond-pulse-pumped Spontaneous Parametric Down-Conversion
We present theoretical and experimental study of preparing maximally
entangled two-photon polarization states, or Bell states, using femtosecond
pulse pumped spontaneous parametric down-conversion (SPDC). First, we show how
the inherent distinguishability in femtosecond pulse pumped type-II SPDC can be
removed by using an interferometric technique without spectral and amplitude
post-selection. We then analyze the recently introduced Bell state preparation
scheme using type-I SPDC. Theoretically, both methods offer the same results,
however, type-I SPDC provides experimentally superior methods of preparing Bell
states in femtosecond pulse pumped SPDC. Such a pulsed source of highly
entangled photon pairs is useful in quantum communications, quantum
cryptography, quantum teleportation, etc.Comment: 11 pages, two-column format, to appear in PR
Supersymmetric AdS_3, AdS_2 and Bubble Solutions
We present new supersymmetric AdS_3 solutions of type IIB supergravity and
AdS_2 solutions of D=11 supergravity. The former are dual to conformal field
theories in two dimensions with N=(0,2) supersymmetry while the latter are dual
to conformal quantum mechanics with two supercharges. Our construction also
includes AdS_2 solutions of D=11 supergravity that have non-compact internal
spaces which are dual to three-dimensional N=2 superconformal field theories
coupled to point-like defects. We also present some new bubble-type solutions,
corresponding to BPS states in conformal theories, that preserve four
supersymmetries.Comment: v2: 33 pages, published version in JHE
First-order interference of nonclassical light emitted spontaneously at different times
We study first-order interference in spontaneous parametric down-conversion
generated by two pump pulses that do not overlap in time. The observed
modulation in the angular distribution of the signal detector counting rate can
only be explained in terms of a quantum mechanical description based on
biphoton states. The condition for observing interference in the signal channel
is shown to depend on the parameters of the idler radiation.Comment: 5 pages, two-column, submitted to PR
Structural Relaxation and Frequency Dependent Specific Heat in a Supercooled Liquid
We have studied the relation between the structural relaxation and the
frequency dependent thermal response or the specific heat, , in a
supercooled liquid.
The Mode Coupling Theory (MCT) results are used to obtain
corresponding to different wavevectors. Due to the two-step
relaxation process present in the MCT, an extra peak, in addition to the low
frequency peak, is predicted in specific heat at high frequency.Comment: 14 pages, 13 Figure
Experimental Entanglement Concentration and Universal Bell-state Synthesizer
We report a novel Bell-state synthesizer in which an interferometric
entanglement concentration scheme is used. An initially mixed polarization
state from type-II spontaneous parametric down-conversion becomes entangled
after the interferometric entanglement concentrator. This Bell-state
synthesizer is universal in the sense that the output polarization state is not
affected by spectral filtering, crystal thickness, and, most importantly, the
choice of pump source. It is also robust against environmental disturbance and
a more general state, partially mixedpartially entangled state, can be
readily generated as well.Comment: Minor update (Newer data
Bounds from Primordial Black Holes with a Near Critical Collapse Initial Mass Function
Recent numerical evidence suggests that a mass spectrum of primordial black
holes (PBHs) is produced as a consequence of near critical gravitational
collapse. Assuming that these holes formed from the initial density
perturbations seeded by inflation, we calculate model independent upper bounds
on the mass variance at the reheating temperature by requiring the mass density
not exceed the critical density and the photon emission not exceed current
diffuse gamma-ray measurements. We then translate these results into bounds on
the spectral index n by utilizing the COBE data to normalize the mass variance
at large scales, assuming a constant power law, then scaling this result to the
reheating temperature. We find that our bounds on n differ substantially
(\delta n > 0.05) from those calculated using initial mass functions derived
under the assumption that the black hole mass is proportional to the horizon
mass at the collapse epoch. We also find a change in the shape of the diffuse
gamma-ray spectrum which results from the Hawking radiation. Finally, we study
the impact of a nonzero cosmological constant and find that the bounds on n are
strengthened considerably if the universe is indeed vacuum-energy dominated
today.Comment: 24 pages, REVTeX, 5 figures; minor typos fixed, two refs added,
version to be published in PR
Apparent finite-size effects in the dynamics of supercooled liquids
Molecular dynamics simulations are performed for a supercooled simple liquid
with changing the system size from N=108 to to examine possible
finite-size effects. Although almost no systematic deviation is detected in the
static pair correlation functions, it is demonstrated that the structural
relaxation in a small system becomes considerably slower than that in
larger systems for temperatures below at which the size of the
cooperative particle motions becomes comparable to the unit cell length of the
small system. The discrepancy increases with decreasing temperature.Comment: 4 pages 5 figure
Constraints on diffuse neutrino background from primordial black holes
We calculated the energy spectra and the fluxes of electron neutrino emitted
in the process of evaporation of primordial black holes (PBHs) in the early
universe. It was assumed that PBHs are formed by a blue power-law spectrum of
primordial density fluctuations. We obtained the bounds on the spectral index
of density fluctuations assuming validity of the standard picture of
gravitational collapse and using the available data of several experiments with
atmospheric and solar neutrinos. The comparison of our results with the
previous constraints (which had been obtained using diffuse photon background
data) shows that such bounds are quite sensitive to an assumed form of the
initial PBH mass function.Comment: 18 pages,(with 7 figures
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