465 research outputs found
Noise in Grover's Quantum Search Algorithm
Grover's quantum algorithm improves any classical search algorithm. We show
how random Gaussian noise at each step of the algorithm can be modelled easily
because of the exact recursion formulas available for computing the quantum
amplitude in Grover's algorithm. We study the algorithm's intrinsic robustness
when no quantum correction codes are used, and evaluate how much noise the
algorithm can bear with, in terms of the size of the phone book and a desired
probability of finding the correct result. The algorithm loses efficiency when
noise is added, but does not slow down. We also study the maximal noise under
which the iterated quantum algorithm is just as slow as the classical
algorithm. In all cases, the width of the allowed noise scales with the size of
the phone book as N^-2/3.Comment: 17 pages, 2 eps figures. Revised version. To be published in PRA,
December 199
Effects of Noisy Oracle on Search Algorithm Complexity
Grover's algorithm provides a quadratic speed-up over classical algorithms
for unstructured database or library searches. This paper examines the
robustness of Grover's search algorithm to a random phase error in the oracle
and analyzes the complexity of the search process as a function of the scaling
of the oracle error with database or library size. Both the discrete- and
continuous-time implementations of the search algorithm are investigated. It is
shown that unless the oracle phase error scales as O(N^(-1/4)), neither the
discrete- nor the continuous-time implementation of Grover's algorithm is
scalably robust to this error in the absence of error correction.Comment: 16 pages, 4 figures, submitted to Phys. Rev.
Implementation of quantum search algorithm using classical Fourier optics
We report on an experiment on Grover's quantum search algorithm showing that
{\em classical waves} can search a -item database as efficiently as quantum
mechanics can. The transverse beam profile of a short laser pulse is processed
iteratively as the pulse bounces back and forth between two mirrors. We
directly observe the sought item being found in iterations, in
the form of a growing intensity peak on this profile. Although the lack of
quantum entanglement limits the {\em size} of our database, our results show
that entanglement is neither necessary for the algorithm itself, nor for its
efficiency.Comment: 4 pages, 3 figures; minor revisions plus extra referenc
Noise effects in the quantum search algorithm from the computational complexity point of view
We analyse the resilience of the quantum search algorithm in the presence of
quantum noise modelled as trace preserving completely positive maps. We study
the influence of noise on computational complexity of the quantum search
algorithm. We show that only for small amounts of noise the quantum search
algorithm is still more efficient than any classical algorithm.Comment: 7 pages, 2 figure
Explaining Cold-Pulse Dynamics in Tokamak Plasmas Using Local Turbulent Transport Models
A long-standing enigma in plasma transport has been resolved by modeling of cold-pulse experiments conducted on the Alcator C-Mod tokamak. Controlled edge cooling of fusion plasmas triggers core electron heating on time scales faster than an energy confinement time, which has long been interpreted as strong evidence of nonlocal transport. This Letter shows that the steady-state profiles, the cold-pulse rise time, and disappearance at higher density as measured in these experiments are successfully captured by a recent local quasilinear turbulent transport model, demonstrating that the existence of nonlocal transport phenomena is not necessary for explaining the behavior and time scales of cold-pulse experiments in tokamak plasmas.United States. Department of Energy (Award DE-FC02-99ER54512)United States. Department of Energy (Grant DESC0014264
Probing the earliest phases in the formation of massive galaxies with simulated HST+JWST imaging data from Illustris
We use the Illustris-1 simulation to explore the capabilities of the
and data to analyze the
stellar populations in high-redshift galaxies, taking advantage of the combined
depth, spatial resolution, and wavelength coverage. For that purpose, we use
simulated broad-band ACS, WFC3 and NIRCam data and 2-dimensional stellar
population synthesis (2D-SPS) to derive the integrated star formation history
(SFH) of massive (MM) simulated galaxies at
M galaxy. In
particular, we explore the potential of HST and JWST datasets reaching a depth
similar to those of the CANDELS and ongoing CEERS observations, respectively,
and concentrate on determining the capabilities of this dataset for
characterizing the first episodes in the SFH of local
MM galaxies by studying their progenitors at
. The 2D-SPS method presented in this paper has been calibrated to
robustly recover the cosmic times when the first star formation episodes
occurred in massive galaxies, i.e., the first stages in their integrated SFHs.
In particular, we discuss the times when the first 1% to 50% of their total
stellar mass formed in the simulation. We demonstrate that we can recover these
ages with typical median systematic offset of less than 5% and scatter around
20%-30%. According to our measurements on Illustris data, we are able to
recover that local MM galaxies would have started
their formation by , forming the first 5% of their stellar mass present
at by , 10% by , and 25% by .Comment: 28 pages, 13 figures, 4 tables. ApJ in press. Summary of changes from
original submission: the major change is that we now include in Sec. 6 the
comparison of the results obtained for our sample of massive 1 < z < 4
progenitors with those obtained by considering all massive galaxies at 1 < z
< 4 in the simulated images. Several figures and sections have been update
FAK acts as a suppressor of RTK-MAP kinase signalling in Drosophila melanogaster epithelia and human cancer cells
Receptor Tyrosine Kinases (RTKs) and Focal Adhesion Kinase (FAK) regulate multiple signalling pathways, including mitogen-activated protein (MAP) kinase pathway. FAK interacts with several RTKs but little is known about how FAK regulates their downstream signalling. Here we investigated how FAK regulates signalling resulting from the overexpression of the RTKs RET and EGFR. FAK suppressed RTKs signalling in Drosophila melanogaster epithelia by impairing MAPK pathway. This regulation was also observed in MDA-MB-231 human breast cancer cells, suggesting it is a conserved phenomenon in humans. Mechanistically, FAK reduced receptor recycling into the plasma membrane, which resulted in lower MAPK activation. Conversely, increasing the membrane pool of the receptor increased MAPK pathway signalling. FAK is widely considered as a therapeutic target in cancer biology; however, it also has tumour suppressor properties in some contexts. Therefore, the FAK-mediated negative regulation of RTK/MAPK signalling described here may have potential implications in the designing of therapy strategies for RTK-driven tumours
NGDEEP Epoch 1: Spatially Resolved H Observations of Disk and Bulge Growth in Star-Forming Galaxies at 0.6-2.2 from JWST NIRISS Slitless Spectroscopy
We study the H equivalent width, EW(H), maps of 19 galaxies
at in the Hubble Ultra Deep Field (HUDF) derived from NIRISS
slitless spectroscopy as part of the Next Generation Deep Extragalactic
Exploratory Public (NGDEEP) Survey. Our galaxies mostly lie on the
star-formation main sequence with a stellar mass range of , and are therefore characteristic of "typical" star-forming
galaxies at these redshifts. Leveraging deep HST and JWST broad-band images,
spanning 0.4-4 m, we perform spatially-resolved fitting of the spectral
energy distributions (SEDs) for these galaxies and construct specific star
formation rate (sSFR) and stellar-mass-weighted age maps. We compare these to
the EW(H) maps with a spatial resolution of 1 kpc. The
pixel-to-pixel EW(H) increases with increasing sSFR and with decreasing
age, with the average trend slightly different from the relations derived from
integrated fluxes of galaxies from the literature. Quantifying the radial
profiles of EW(H), sSFR, and age, the majority (84%) of galaxies show
positive EW(H) gradients, positive sSFR gradients, and negative age
gradients, in line with the the inside-out quenching scenario. A few galaxies
(16%) show inverse (and flat) trends possibly due to merging or starbursts.
Comparing the distributions of EW(H) and sSFR to the star formation
history models as a function of galactocentric radius, the central region of
galaxies (e.g., their bulges) have experienced, at least one, rapid
star-formation episodes, which leads to the formation of bulge, while their
outer regions (e.g., disks) grow in a more steady-state. These results
demonstrate the ability to study resolved star formation in distant galaxies
with JWST NIRISS.Comment: 22 pages, 11 figure
CEERS: Spatially Resolved UV and mid-IR Star Formation in Galaxies at 0.2 < z < 2.5: The Picture from the Hubble and James Webb Space Telescopes
We present the mid-IR (MIR) morphologies for 64 star-forming galaxies at
0.210^{9}~M_\odot} using JWST MIRI
observations from the Cosmic Evolution Early Release Science survey (CEERS).
The MIRI bands span the MIR (7.7--21~m), enabling us to measure the
effective radii () and S\'{e}rsic indexes of these SFGs at
rest-frame 6.2 and 7.7 m, which contains strong emission from Polycyclic
aromatic hydrocarbon (PAH) features, a well-established tracer of star
formation in galaxies. We define a ``PAH-band'' as the MIRI bandpass that
contains these features at the redshift of the galaxy. We then compare the
galaxy morphologies in the PAH-bands to those in rest-frame Near-UV (NUV) using
HST ACS/F435W or ACS/F606W and optical/near-IR using HST WFC3/F160W imaging
from UVCANDELS and CANDELS, where the NUV-band and F160W trace the profile of
(unobscured) massive stars and the stellar continuum, respectively. The
of galaxies in the PAH-band are slightly smaller (10\%)
than those in F160W for galaxies with at
, but the PAH-band and F160W have a similar fractions of light within
1 kpc. In contrast, the of galaxies in the NUV-band are larger,
with lower fractions of light within 1 kpc compared to F160W for galaxies at
. Using the MIRI data to estimate the surface
density, we find the correlation between the surface
density and stellar mass has a steeper slope than that of the
surface density and stellar mass, suggesting more massive
galaxies having increasing amounts of obscured fraction of star formation in
their inner regions. This paper demonstrates how the high-angular resolution
data from JWST/MIRI can reveal new information about the morphology of
obscured-star formation.Comment: 28 pages, 11 figures, Accepted by Ap
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