140 research outputs found
Criticality, factorization and long-range correlations in the anisotropic XY-model
We study the long-range quantum correlations in the anisotropic XY-model. By
first examining the thermodynamic limit we show that employing the quantum
discord as a figure of merit allows one to capture the main features of the
model at zero temperature. Further, by considering suitably large site
separations we find that these correlations obey a simple scaling behavior for
finite temperatures, allowing for efficient estimation of the critical point.
We also address ground-state factorization of this model by explicitly
considering finite size systems, showing its relation to the energy spectrum
and explaining the persistence of the phenomenon at finite temperatures.
Finally, we compute the fidelity between finite and infinite systems in order
to show that remarkably small system sizes can closely approximate the
thermodynamic limit.Comment: 8 pages, 8 figures. Close to published versio
Quenching small quantum gases: Genesis of the orthogonality catastrophe
We study the dynamics of two strongly interacting bosons with an additional
impurity atom trapped in a harmonic potential. Using exact numerical
diagonalization we are able to fully explore the dynamical evolution when the
interaction between the two distinct species is suddenly switched on
(quenched). We examine the behavior of the densities, the entanglement, the
Loschmidt echo and the spectral function for a large range of inter-species
interactions and find that even in such small systems evidence of Anderson's
orthogonality catastrophe can be witnessed.Comment: 6 pages, 5 figures, Accepted for publication in Physical Review
An efficient non-linear Feshbach engine
We investigate a thermodynamic cycle using a Bose-Einstein condensate with
nonlinear interactions as the working medium. Exploiting Feshbach resonances to
change the interaction strength of the BEC allows us to produce work by
expanding and compressing the gas. To ensure a large power output from this
engine these strokes must be performed on a short timescale, however such
non-adiabatic strokes can create irreversible work which degrades the engine's
efficiency. To combat this, we design a shortcut to adiabaticity which can
achieve an adiabatic-like evolution within a finite time, therefore
significantly reducing the out-of-equilibrium excitations in the BEC. We
investigate the effect of the shortcut to adiabaticity on the efficiency and
power output of the engine and show that the tunable nonlinearity strength,
modulated by Feshbach resonances, serves as a useful tool to enhance the
system's performance.Comment: 8 pages, 5 figures. To Appear New J. Phys. Focus on Shortcuts to
Adiabaticit
Method of fabricating a nanochannel system for DNA sequencing and nanoparticle characterization
A process for fabricating a nanochannel system using a combination of microelectromechanical system (MEMS) microfabrication techniques, atomic force microscopy (AFM) nanolithography, and focused ion beam (FIB). The nanochannel system, fabricated on either a glass or silicon substrate, has channel heights and widths on the order of single to tens of nanometers. The channel length is in the micrometer range. The nanochannel system is equipped with embedded micro and nanoscale electrodes, positioned along the length of the nanochannel for electron tunneling based characterization of nanoscale particles in the channel. Anodic bonding is used to cap off the nanochannel with a cover chip
Orthogonality Catastrophe as a Consequence of the Quantum Speed Limit
A remarkable feature of quantum many-body systems is the orthogonality catastrophe that describes their extensively growing sensitivity to local perturbations and plays an important role in condensed matter physics. Here we show that the dynamics of the orthogonality catastrophe can be fully characterized by the quantum speed limit and, more specifically, that any quenched quantum many-body system, whose variance in ground state energy scales with the system size, exhibits the orthogonality catastrophe. Our rigorous findings are demonstrated by two paradigmatic classes of many-body systems—the trapped Fermi gas and the long-range interacting Lipkin-Meshkov-Glick spin model
Method of fabricating a nanochannel system for DNA sequencing and nanoparticle characterization
A process for fabricating a nanochannel system using a combination of microelectromechanical system (MEMS) microfabrication techniques, atomic force microscopy (AFM) nanolithography, and focused ion beam (FIB). The nanochannel system, fabricated on either a glass or silicon substrate, has channel heights and widths on the order of single to tens of nanometers. The channel length is in the micrometer range. The nanochannel system is equipped with embedded micro and nanoscale electrodes, positioned along the length of the nanochannel for electron tunneling based characterization of nanoscale particles in the channel. Anodic bonding is used to cap off the nanochannel with a cover chip
Non-equilibrium thermodynamics of harmonically trapped bosons
We apply the framework of non-equilibrium quantum thermodynamics to the
physics of quenched small-sized bosonic quantum gases in a one-dimensional
harmonic trap. We show that dynamical orthogonality can occur in these few-body
systems with strong interactions after a quench and we find its occurrence
analytically for an infinitely repulsive pair of atoms. We further show this
phenomena is related to the fundamental excitations that dictate the dynamics
from the spectral function. We establish a clear qualitative link between the
amount of (irreversible) work performed on the system and the establishment of
entanglement. We extend our analysis to multipartite systems by examining the
case of three trapped atoms. We show the initial (pre-quench) interactions play
a vital role in determining the dynamical features, while the qualitative
features of the two particle case appear to remain valid. Finally, we propose
the use of the atomic density profile as a readily accessible indicator of the
non-equilibrium properties of the systems in question.Comment: Short supplementary section available in source files. Close to
published version. v4 included an omitted referenc
In situ thermometry of a cold Fermi gas via dephasing impurities
The precise measurement of low temperatures is a challenging, important and
fundamental task for quantum science. In particular, in-situ thermometry is
highly desirable for cold atomic systems due to their potential for quantum
simulation. Here we demonstrate that the temperature of a non-interacting Fermi
gas can be accurately inferred from the non-equilibrium dynamics of impurities
immersed within it, using an interferometric protocol and established
experimental methods. Adopting tools from the theory of quantum parameter
estimation, we show that our proposed scheme achieves optimal precision in the
relevant temperature regime for degenerate Fermi gases in current experiments.
We also discover an intriguing trade-off between measurement time and
thermometric precision that is controlled by the impurity-gas coupling, with
weak coupling leading to the greatest sensitivities. This is explained as a
consequence of the slow decoherence associated with the onset of the Anderson
orthogonality catastrophe, which dominates the gas dynamics following its local
interaction with the immersed impurity.Comment: 6+5 pages, 4+4 figures. Final author versio
MiRP1 forms IKr potassium channels with HERG and is associated with cardiac arrhythmia.
A novel potassium channel gene has been cloned, characterized, and associated with cardiac arrhythmia. The gene encodes MinK-related peptide 1 (MiRP1), a small integral membrane subunit that assembles with HERG, a pore-forming protein, to alter its function. Unlike channels formed only with HERG, mixed complexes resemble native cardiac IKr channels in their gating, unitary conductance, regulation by potassium, and distinctive biphasic inhibition by the class III antiarrhythmic E-4031. Three missense mutations associated with long QT syndrome and ventricular fibrillation are identified in the gene for MiRP1. Mutants form channels that open slowly and close rapidly, thereby diminishing potassium currents. One variant, associated with clarithromycin-induced arrhythmia, increases channel blockade by the antibiotic. A mechanism for acquired arrhythmia is revealed: genetically based reduction in potassium currents that remains clinically silent until combined with additional stressors
The challenges of detecting and attributing ocean acidification impacts on marine ecosystems
© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Doo, S. S., Kealoha, A., Andersson, A., Cohen, A. L., Hicks, T. L., Johnson, Z., I., Long, M. H., McElhany, P., Mollica, N., Shamberger, K. E. F., Silbiger, N. J., Takeshita, Y., & Busch, D. S. The challenges of detecting and attributing ocean acidification impacts on marine ecosystems. ICES Journal of Marine Science, 77(7-8), (2020): 2411-2422, https://doi.org/10.1093/icesjms/fsaa094.A substantial body of research now exists demonstrating sensitivities of marine organisms to ocean acidification (OA) in laboratory settings. However, corresponding in situ observations of marine species or ecosystem changes that can be unequivocally attributed to anthropogenic OA are limited. Challenges remain in detecting and attributing OA effects in nature, in part because multiple environmental changes are co-occurring with OA, all of which have the potential to influence marine ecosystem responses. Furthermore, the change in ocean pH since the industrial revolution is small relative to the natural variability within many systems, making it difficult to detect, and in some cases, has yet to cross physiological thresholds. The small number of studies that clearly document OA impacts in nature cannot be interpreted as a lack of larger-scale attributable impacts at the present time or in the future but highlights the need for innovative research approaches and analyses. We summarize the general findings in four relatively well-studied marine groups (seagrasses, pteropods, oysters, and coral reefs) and integrate overarching themes to highlight the challenges involved in detecting and attributing the effects of OA in natural environments. We then discuss four potential strategies to better evaluate and attribute OA impacts on species and ecosystems. First, we highlight the need for work quantifying the anthropogenic input of CO2 in coastal and open-ocean waters to understand how this increase in CO2 interacts with other physical and chemical factors to drive organismal conditions. Second, understanding OA-induced changes in population-level demography, potentially increased sensitivities in certain life stages, and how these effects scale to ecosystem-level processes (e.g. community metabolism) will improve our ability to attribute impacts to OA among co-varying parameters. Third, there is a great need to understand the potential modulation of OA impacts through the interplay of ecology and evolution (eco–evo dynamics). Lastly, further research efforts designed to detect, quantify, and project the effects of OA on marine organisms and ecosystems utilizing a comparative approach with long-term data sets will also provide critical information for informing the management of marine ecosystems.SSD was funded by NSF OCE (grant # 1415268). DSB and PM were supported by the NOAA Ocean Acidification Program and Northwest Fisheries Science Center, MHL was supported by NSF OCE (grant # 1633951), ZIJ was supported by NSF OCE (grant # 1416665) and DOE EERE (grant #DE-EE008518), NJS was supported by NSF OCE (grant # 1924281), ALC was supported by NSF OCE (grant # 1737311), and AA was supported by NSF OCE (grant # 1416518). KEFS, AK, and TLH were supported by Texas A&M University. This is CSUN Marine Biology contribution (# 306)
- …