arXiv subjects

Stephen W. Teitsworth

Publications and source records attributed to Stephen W. Teitsworth.

11 recordsLinked to original sources

arXiv2026

Quantum-classical crossover in noisy monitored oscillators

The quantum first-passage problem involves stochastic trajectories conditioned on measurement outcomes. The timing statistics of such trajectories remain largely unexplored in open quantum systems. Here, we investigate the first-passage time to an energy threshold for a ubiquitous model: a harmonic oscillator driven by classical additive noise. We find that projective measurements and energy quantization lead to substantial differences between the quantum and classical first-passage-time distributions at low thresholds, while these differences gradually diminish as the threshold energy increases. We treat the problem using both ensemble-averaged conditioned density-matrix dynamics and trajectory-resolved stochastic pure-state dynamics. The two descriptions yield indistinguishable timing statistics. Quantization effects appear in the ensemble-level phase-space distributions of the surviving states and vanish at larger threshold energies. Individual trajectories reveal emergent quantum signatures from the repeated measurements, such as persistent Wigner negativity. Our results provide a framework for using first-passage processes to create measurement-induced nonclassical resource states and to study the quantum-classical crossover of monitored systems.

quant-ph↗

arXiv2026

Experimental measurement of quantum first-passage-time distributions

Classical First-Passage-Time Distributions (FPTDs) have been extensively studied both theoretically and experimentally. Their quantum counterparts-Quantum First-Passage-Time Distributions (QFPTDs)-remain largely unexplored and have deep implications for both fundamental physics and the development of emerging quantum technologies. We measure the first QFPTDs using a motional mode of a single trapped ion. We develop a novel composite-phase laser pulse sequence to perform tunable stroboscopic single-shot projective measurements of the motional state of a trapped ion. We measure QFPTDs of the ion energy when coupled to electric-field noise. The measurement protocol developed here is broadly applicable to other quantum systems and provides a powerful method for exploring a broad range of QFPTD phenomena. With these results we open a new field of experimental investigations of QFPT processes with potential future relevance to quantum search algorithms, unraveling connections between classical and quantum dynamics, and study of the quantum measurement problem.

quant-ph↗

arXiv2024

Irreversible dynamics of a continuum driven by active matter

We study the fluctuational behavior of overdamped elastic filaments (e.g., strings or rods) driven by active matter which induces irreversibility. The statistics of discrete normal modes are translated into the continuum of the position representation which allows discernment of the spatial structure of dissipation and fluctuational work done by the active forces. The mapping of force statistics onto filament statistics leads to a generalized fluctuation-dissipation relation which predicts the components of the stochastic area tensor and its spatial proxy, the irreversibility field. We illustrate the general theory with explicit results for a tensioned string between two fixed endpoints. Plots of the stochastic area tensor components in the discrete plane of mode pairs reveal how the active forces induce spatial correlations of displacement along the filament. The irreversibility field provides additional quantitative insight into the relative spatial distributions of fluctuational work and dissipative response.

cond-mat.soft↗

arXiv2019

Experimental metrics for detection of detailed balance violation

We report on the measurement of detailed balance violation in a coupled, noise-driven linear electronic circuit consisting of two nominally identical RC elements that are coupled via a variable capacitance. The state variables are the time-dependent voltages across each of the two primary capacitors, and the system is driven by independent noise sources in series with each of the resistances. From the recorded time histories of these two voltages, we quantify violations of detailed balance by three methods: 1) explicit construction of the probability current density, 2) by constructing the time-dependent stochastic area, and 3) by constructing statistical fluctuation loops. In comparing the three methods, we find that the stochastic area is relatively simple to implement, computationally inexpensive, and provides a highly sensitive means for detecting violations of detailed balance.

cond-mat.stat-mech↗

arXiv2019

Scaling properties of noise-induced switching in a bistable tunnel diode circuit

Noise-induced switching between coexisting metastable states occurs in a wide range of far-from-equilibrium systems including micro-mechanical oscillators, epidemiological and climate change models, and nonlinear electronic transport in tunneling structures such as semiconductor superlattices and tunnel diodes. In the case of tunnel diode circuits, noise-induced switching behavior is associated with negative differential resistance in the static current-voltage characteristics and bistability, i.e., the existence of two macroscopic current states for a given applied voltage. Noise effects are particularly strong near the onset and offset of bistable current behavior, corresponding to bifurcation points in the associated dynamical system. In this paper, we show that the tunnel diode system provides an excellent experimental platform for the precision measurement of scaling properties of mean switching times versus applied voltage near bifurcation points. More specifically, experimental data confirm that the mean switching time scales logarithmically as the 3/2 power of voltage difference over an exceptionally wide range of time scales and noise intensities.

cond-mat.stat-mech↗

arXiv2014

Steering most probable escape paths by varying relative noise intensities

We demonstrate the possibility to systematically steer the most probable escape paths (MPEPs) by adjusting relative noise intensities in dynamical systems that exhibit noise-induced escape from a metastable point via a saddle point. Using a geometric minimum action approach, an asymptotic theory is developed which is broadly applicable to fast-slow systems and shows the important role played by the nullcline associated with the fast variable in locating the MPEPs. A two-dimensional quadratic system is presented which permits analytical determination of both the MPEPs and associated action values. Analytical predictions agree with computed MPEPs, and both are numerically confirmed by constructing prehistory distributions directly from the underlying stochastic differential equation.

cond-mat.stat-mech↗

arXiv2010

Symmetry-breaking transitions in networks of nonlinear circuit elements

We investigate a nonlinear circuit consisting of N tunnel diodes in series, which shows close similarities to a semiconductor superlattice or to a neural network. Each tunnel diode is modeled by a three-variable FitzHugh-Nagumo-like system. The tunnel diodes are coupled globally through a load resistor. We find complex bifurcation scenarios with symmetry-breaking transitions that generate multiple fixed points off the synchronization manifold. We show that multiply degenerate zero-eigenvalue bifurcations occur, which lead to multistable current branches, and that these bifurcations are also degenerate with a Hopf bifurcation. These predicted scenarios of multiple branches and degenerate bifurcations are also found experimentally.

nlin.CD↗

arXiv2010

Rare Transition Events in Nonequilibrium Systems with State-Dependent Noise: Application to Stochastic Current Switching in Semiconductor Superlattices

Using recent mathematical advances, a geometric approach to rare noise-driven transition events in nonequilibrium systems is given, and an algorithm for computing the maximum likelihood transition curve is generalized to the case of state-dependent noise. It is applied to a model of electronic transport in semiconductor superlattices to investigate transitions between metastable electric field distributions. When the applied voltage $V$ is varied near a saddle-node bifurcation at $V_th$, the mean life time $ $ of the initial metastable state is shown to scale like $log \propto |V_th - V|^{3/2}$ as $V\to V_th$.

math.PR↗

arXiv2010

Emergence of current branches in a series array of negative differential resistance circuit elements

We study a series array of nonlinear electrical circuit elements that possess negative differential resistance and find that \emph{heterogeneity} in the element properties leads to the presence of multiple branches in current-voltage curves and a non-uniform distribution of voltages across the elements. An inhomogeneity parameter $r_{max}$ is introduced to characterize the extent to which the individual element voltages deviate from one another, and it is found to be strongly dependent on the rate of change of applied voltage. Analytical expressions are derived for the dependence of $r_{max}$ on voltage ramping rate in the limit of fast ramping and are confirmed by direct numerical simulation.

cond-mat.mtrl-sci↗

arXiv2009

Dynamics of electronic transport in a semiconductor superlattice with a shunting side layer

We study a model describing electronic transport in a weakly-coupled semiconductor superlattice with a shunting side layer. Key parameters include the lateral size of the superlattice, the connectivity between the quantum wells of the superlattice and the shunt layer, and the conduction properties of the shunt layer. For a superlattice with small lateral extent and high quality shunt, static electric field domains are suppressed and a spatially-uniform field configuration is predicted to be stable, a result that may be useful for proposed devices such as a superlattice-based TeraHertz (THz) oscillators. As the lateral size of the superlattice increases, the uniform field configuration loses its stability to either static or dynamic field domains, regardless of shunt properties. A lower quality shunt generally leads to regular and chaotic current oscillations and complex spatio-temporal dynamics in the field profile. Bifurcations separating static and dynamic behaviors are characterized and found to be dependent on the shunt properties.

cond-mat.mtrl-sci↗

arXiv2001

Scarring in vibrational modes of thin metal plates

We report the first direct experimental observation of scarring phenomenon in transverse vibrational modes of a thin metal plate. The plate has the shape of a full stadium and clamped boundary conditions. Normal modes are imaged using time-averaged holographic interferometry, and modes corresponding to ``bouncing ball'' and higher order periodic trajectories are found. An eikonal approximation of the solution along classical trajectories of the stadium including nontrivial phase shifts at clamped boundaries yields a useful quantization condition for the observed modes.

nlin.CD↗