arXiv subjects

Isabella L. Giovannelli

Publications and source records attributed to Isabella L. Giovannelli.

3 recordsLinked to original sources

arXiv2026

Chirped Pulse Analysis and Control in Non-Hermitian Scattering Systems using Complex Time Delay

We theoretically and experimentally establish a connection between linearly chirped pulse propagation properties and the complex generalization of Wigner-Smith time delay for both transmitted and reflected pulses in linear and dispersive reverberant non-Hermitian scattering systems. We demonstrate that the time shift of the chirped pulse depends on both the real and imaginary parts of the complex time delay of the scattering system. We also show that the chirped pulse experiences a center frequency shift that is directly proportional to the imaginary component of complex time delay, similar to that found in Giovannelli and Anlage (2025). Using these insights, we then demonstrate how complex time delay can be harnessed to systematically tune the propagation properties of a chirped pulse such that a near-zero time shift can be achieved for a wide range of pulse center frequencies in a resonant scattering system. Overall, this work broadens the utility and establishes the physical significance of complex time delays in non-Hermitian settings.

physics.optics↗

arXiv2025

A Physical Interpretation of Imaginary Time Delay

The scattering matrix $S$ linearly relates the vector of incoming waves to outgoing wave excitations, and contains an enormous amount of information about the scattering system and its connections to the scattering channels. Time delay is one way to extract information from $S$, and the transmission time delay $τ_T$ is a complex (even for Hermitian systems with unitary scattering matrices) measure of how long a wave excitation lingers before being transmitted. The real part of $τ_T$ is a well-studied quantity, but the imaginary part of $τ_T$ has not been systematically examined experimentally, and theoretical predictions for its behavior have not been tested. Here we experimentally test the predictions of Asano, et al. [Nat. Comm. 7, 13488 (2016)] for the imaginary part of transmission time delay in a non-unitary scattering system. We utilize Gaussian time-domain pulses scattering from a 2-port microwave graph supporting a series of well-isolated absorptive modes to show that the carrier frequency of the pulses is changed in the scattering process by an amount in agreement with the imaginary part of the independently determined complex transmission time delay, $\text{Im}[τ_T]$, from frequency-domain measurements of the sub-unitary $S$ matrix. Our results also generalize and extend those of Asano, et al., establishing a means to predict pulse propagation properties of non-Hermitian systems over a broad range of conditions.

physics.optics↗

arXiv2024

Asymmetric Transmission Through a Classical Analogue of the Aharonov-Bohm Ring

It has been predicted that new physics and technology are enabled for quantum systems that suffer from partial decoherence, in the intermediate range between coherent quantum evolution and incoherent classical physics. We explore the asymmetric transmission through a classical analogue of the Aharonov-Bohm (AB) mesoscopic ring that supports a 3:1 asymmetry in transmission times, augmented with lossy features that act preferentially on the longer-lingering waves. Such a device is realized as a linear microwave graph utilizing a gyrator to create the 3:1 transmission time delay asymmetry, along with both homogeneous and localized losses, to produce an imbalance in wave transmission through the device. We demonstrate asymmetric transmission through the microwave-ring graph as a function of loss in both simulation and experiment, and in both the frequency- and time-domain. The microwave ring-graph results are compared to a numerical simulation representative of a class of recent models proposing dephasing-induced transport asymmetry in few-channel quantum systems, and parallels are noted.

quant-ph↗