arXiv subjects

Joshua Chiel

Publications and source records attributed to Joshua Chiel.

5 recordsLinked to original sources

arXiv2024

Dynamically Robust Counterdiabatic Topological Pumping

Thouless pumping is a transport phenomenon whereby an insulating, time-periodic Hamiltonian induces a robustly quantized transfer of charge, per driving cycle, in the quasi-adiabatic limit. In this work we apply the shortcuts to adiabaticity (STA) method of counterdiabatic (CD) driving to the Rice-Mele model, an archetypal model for Thouless pumping. We show that the charge pumped rapidly across each bond of our CD Rice-Mele model is robustly quantized and determined by a Chern number. The CD Hamiltonian generally involves long-range, hence non-local, hopping. Therefore we also derive an exact, local, nearest-neighbor CD Hamiltonian for our lattice system. We show that our nearest neighbor non-adiabatic protocol possesses the same topological robustness to onsite disorder as quasi-adiabatic Thouless pumps and is moreover surprisingly robust to onsite disorder and noise errors in implementing the CD protocol, for sufficiently rapid driving. The protocol also reproduces finite-temperature Thouless pump results away from the adiabatic limit. In addition, we develop a general method to produce non-trivial, finite-time quantized pumping starting from any Rice-Mele initial ground state using only nearest-neighbor hopping.

quant-ph↗

arXiv2021

Shortcuts in stochastic systems and control of biophysical processes

The biochemical reaction networks that regulate living systems are all stochastic to varying degrees. The resulting randomness affects biological outcomes at multiple scales, from the functional states of single proteins in a cell to the evolutionary trajectory of whole populations. Controlling how the distribution of these outcomes changes over time -- via external interventions like time-varying concentrations of chemical species -- is a complex challenge. In this work, we show how counterdiabatic (CD) driving, first developed to control quantum systems, provides a versatile tool for steering biological processes. We develop a practical graph-theoretic framework for CD driving in discrete-state continuous-time Markov networks. Though CD driving is limited to target trajectories that are instantaneous stationary states, we show how to generalize the approach to allow for non-stationary targets and local control -- where only a subset of system states are targeted. The latter is particularly useful for biological implementations where there may be only a small number of available external control knobs, insufficient for global control. We derive simple graphical criteria for when local versus global control is possible. Finally, we illustrate the formalism with global control of a genetic regulatory switch and local control in chaperone-assisted protein folding. The derived control protocols in the chaperone system closely resemble natural control strategies seen in experimental measurements of heat shock response in yeast and E. coli.

cond-mat.stat-mech↗

arXiv2020

Controlling the speed and trajectory of evolution with counterdiabatic driving

The pace and unpredictability of evolution are critically relevant in a variety of modern challenges: combating drug resistance in pathogens and cancer, understanding how species respond to environmental perturbations like climate change, and developing artificial selection approaches for agriculture. Great progress has been made in quantitative modeling of evolution using fitness landscapes, allowing a degree of prediction for future evolutionary histories. Yet fine-grained control of the speed and the distributions of these trajectories remains elusive. We propose an approach to achieve this using ideas originally developed in a completely different context: counterdiabatic driving to control the behavior of quantum states for applications like quantum computing and manipulating ultra-cold atoms. Implementing these ideas for the first time in a biological context, we show how a set of external control parameters (i.e. varying drug concentrations / types, temperature, nutrients) can guide the probability distribution of genotypes in a population along a specified path and time interval. This level of control, allowing empirical optimization of evolutionary speed and trajectories, has myriad potential applications, from enhancing adaptive therapies for diseases, to the development of thermotolerant crops in preparation for climate change, to accelerating bioengineering methods built on evolutionary models, like directed evolution of biomolecules.

cond-mat.stat-mech↗

arXiv2019

Symmetry breaking, strain solitons and mechanical edge modes in monolayer antimony

Two-dimensional materials exhibit a variety of mechanical instabilities accompanied by spontaneous symmetry breaking. Here we develop a continuum description of the buckling instability of antimonene sheets. Regions of oppositely directed buckling constitute domains separated by domain walls that are solitons in our model. Perturbations about equilibrium propagate as waves with a gapped dispersion in the bulk but there is a gapless mode with linear dispersion that propagates along the domain walls in a manner reminiscent of the electronic modes of topological insulators. We establish that monolayer antimonene is a mechanical topological insulator by demonstrating a mapping between our continuum model and an underlying Dirac equation of the symmetry class BDI which is known to be a topological insulator in one dimension and a weak topological insulator in two dimensions. Monolayer antimony can be produced by exfoliation as well as epitaxy and the effects predicted in this paper should be accessible to standard experimental tools such as scanning probe microscopy and Raman spectroscopy. We surmise that the effects studied here (namely low scale symmetry breaking, strain solitons and gapless edge modes) are not limited to antimonene but are common features of two dimensional materials.

cond-mat.mes-hall↗

arXiv2016

Reconsidering seismological constraints on the available parameter space of macroscopic dark matter

Using lunar seismological data, constraints have been proposed on the available parameter space of macroscopic dark matter (macros). We show that actual limits are considerably weaker by considering in greater detail the mechanism through which macro impacts generate detectable seismic waves, which have wavelengths considerably longer than the diameter of the macro. We show that the portion of the macro parameter space that can be ruled out by current seismological evidence is considerably smaller than previously reported, and specifically that candidates with greater than or equal to nuclear density are not excluded by lunar seismology.

astro-ph.CO↗