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Hervé Lissek

Publications and source records attributed to Hervé Lissek.

13 recordsLinked to original sources

Classical Analog Emulation of Quantum Circuits via Time-Averaged Dynamic States

Classical analog hardware that emulates quantum circuits at the gate level offers a route to benchmarking, prototyping, and teaching quantum algorithms. We introduce wavebits, classical wave analogs of qubits whose amplitudes are carried by physical oscillatory signals, and show that any nonseparable N-qubit state can be encoded in 2N narrowband signals that remain locally separable at every instant. The nonseparable correlations are recovered at readout by time-averaged demodulation over auxiliary carrier frequencies, referred to as nonseparability channels. We prove that any two-qubit gate unravels into the time-averaged tensor product of two local time-varying operators, and that arbitrary circuits are emulated with a base-frequency count scaling linearly with the number of entangling layers, independent of qubit number. The exponential cost of the 2^N-dimensional state reappears at readout and in the averaging time of deep circuits, not during circuit execution, as quantified by an analytic error bound that also serves as a hardware design rule. A mixed-signal prototype emulates Bell state generation, controlled-NOT gates, phase kickback, and Bloch-sphere rotations with fidelities above 0.98, and numerical benchmarks against exact state vectors validate the scheme for up to six qubits. The architecture is directly implementable in acoustic, photonic, and mixed-signal platforms.

quant-ph↗

Transient Vibroacoustic Control of a Shock-Loaded Inter-Connected Cylindrical Double Shell

Double-wall cylindrical shells are widely used in applications where resistance to acoustic shock loading is critical. While the transient vibroacoustic behavior of single-walled shells has been extensively investigated, extending these analyses to double-wall cylindrical configurations introduces increased complexity due to multiple inter-shell acoustic reflections and strong coupling between acoustic fields and structural vibrations. These structures often feature mechanical interconnections between the shells to ensure structural integrity, load sharing, alignment, and enhanced resilience against static and dynamic loads. These links introduce additional pathways for vibration transmission and significantly influence the overall behavior of the system, thus making the analytical description of the coupled vibroacoustic response even more challenging. This study investigates the transient vibroacoustics of an inter-connected double-wall cylindrical shell subjected to an acoustic shock, considering fully coupled fluid-structure interactions. A comprehensive two-dimensional acoustoelastic model is developed in polar coordinates, incorporating the surrounding medium, the fluid occupying the inter-shell gap, and the fluid inside the inner shell. A semi-analytical solution method is employed to capture the time-domain evolution of acoustic fields and shell vibrations. The model's accuracy is verified by benchmarking against available data reported in the literature. Leveraging the passive dynamics of the system, we present a hybrid mechanism that integrates optimized nonlinear vibration absorbers with piezoelectric actuators to control the vibroacoustic behavior. The results demonstrate the effectiveness of the proposed hybrid mechanism in mitigating shock-induced acoustic pressure waves and enhancing the structural resilience of the double-wall cylindrical shell.

physics.app-ph↗

Observation of amplitude-driven nonreciprocity for energy guiding

The non-Hermitian skin effect is an intriguing physical phenomenon, in which all eigen-modes of a non-Hermitian lattice become localized at boundary regions. While such an exotic behavior has been demonstrated in various physical platforms, most realizations have been so far restricted to the linear regime. Here, we explore the cooperation between nonlinearity and the non-Hermitian skin effect, revealing extraordinary amplitude-driven skin localization dynamics. By introducing an extension to the Hatano-Nelson model where couplings inherent nonlinear behavior, we demonstrate the existence of unique amplitude-driven non-Hermitian skin modes capable of concentrating the energy of a source at any point of space, depending on the power level. Our theoretical model is supported by numerical simulations and experimental realization via a highly configurable acoustic metamaterial composed of active electroacoustic resonators. In all, our findings open up exciting paths for a new generation of non-reciprocal systems, in which nonlinearities serve as a strategic tuning knob to manipulate the guiding process.

physics.app-ph↗

Practical realization of chiral nonlinearity for strong topological protection

Nonlinear topology has been much less inquired compared to its linear counterpart. Existing advances have focused on nonlinearities of limited magnitudes and fairly homogeneous types. As such, the realizations have rarely been concerned with the requirements for nonlinearity. Here we explore nonlinear topological protection by determining nonlinear rules and demonstrate their relevance in real-world experiments. We take advantage of chiral symmetry and identify the condition for its continuation in general nonlinear environments. Applying it to one-dimensional topological lattices, we show possible evolution paths for zero-energy edge states that preserve topologically nontrivial phases regardless of the specifics of the chiral nonlinearities. Based on an acoustic prototype design with non-local nonlinearities, we theoretically, numerically, and experimentally implement the nonlinear topological edge states that persist in all nonlinear degrees and directions without any frequency shift. Our findings unveil a broad family of nonlinearities compatible with topological non-triviality, establishing a solid ground for future drilling in the emergent field of nonlinear topology.

cond-mat.mes-hall↗

Hybrid broadband conduction and amplitude-driven topological confinement of sound via synthetic acoustic crystals

Precise wave manipulation has undoubtedly forged the technological landscape we thrive in today. Although our understanding of wave phenomena has come a long way since the earliest observations of desert dunes or ocean waves, the unimpeded development of mathematics has enabled ever more complex and exotic physical phenomena to be comprehensively described. Here, we take wave manipulation a step further by introducing an unprecedented synthetic acoustic crystal capable of realizing simultaneous linear broadband conduction and nonlinear topological insulation, depicting a robust amplitude-dependent mode localized deep within - i.e. an amplitude-driven topological confinement of sound. The latter is achieved by means of an open acoustic waveguide lined with a chain of nonlocally and nonlinearly coupled active electroacoustic resonators. Starting from a comprehensive topological model for classical waves, we demonstrate that different topological regimes can be accessed by increasing driving amplitude and that topological robustness against coupling disorder is a direct consequence of symmetric and simultaneous response between coupled resonators. Theoretical predictions are validated by a fully programmable experimental apparatus capable of realizing the real-time manipulation of metacrystal properties. In all, our results provide a solid foundation for future research in the design and manipulation of classical waves in artificial materials involving nonlinearity, nonlocality, and non-hermiticity.

physics.app-ph↗

Active Su-Schrieffer-Heeger-like System

An acoustic dimer composed of two electronically controlled electro-acoustic resonators is presented in view of exploring one-dimensional topological phenomena.

physics.app-ph↗

Robust direct acoustic impedance control using two microphones for mixed feedforward-feedback controller

This paper presents an acoustic impedance control architecture for an electroacoustic absorber combining both a feedforward and a feedback microphone-based strategies on a current-driven loudspeaker. Feedforward systems enable good performance for direct impedance control. However, inaccuracies in the required actuator model can lead to a loss of passivity, which can cause unstable behaviors. The feedback contribution allows the absorber to better handle model errors and still achieve an accurate impedance, preserving passivity. Numerical and experimental studies were conducted to compare this new architecture against a state-of-the-art feedforward control method.

eess.SY↗

Ultrabroadband sound control with deep-subwavelength plasmacoustic metalayers

Controlling audible sound requires inherently broadband and subwavelength acoustic solutions, which are to date, crucially missing. This includes current noise absorption methods, such as porous materials or acoustic resonators, which are typically inefficient below 1 kHz, or fundamentally narrowband. Here, we solve this vexing issue by introducing the concept of plasmacoustic metalayers. We demonstrate that the dynamics of small layers of air plasma can be controlled to interact with sound in an ultrabroadband way and over deep-subwavelength distances. Exploiting the unique physics of plasmacoustic metalayers, we experimentally demonstrate perfect sound absorption and tunable acoustic reflection over more than two frequency decades, from several Hz to the kHz range, with transparent plasma layers of thicknesses down to $λ/1000$. Such unprecedented bandwidth and compactness opens new doors in a variety of applications, including noise control, audio-engineering, room acoustics, imaging and metamaterial design.

physics.app-ph↗

Corona Discharge Actuator as an Active Sound Absorber Under Normal and Oblique Incidence

In the majority of active sound absorbing systems, a conventional electrodynamic loudspeaker is used as a controlled source. However, particular situations may require an actuator that is more resistant to harsh environments, adjustable in shape, and lighter. In this work, a plasma-based electroacoustic actuator operating on the atmospheric corona discharge principle is used to achieve sound absorption in real-time. Two control strategies are introduced and tested for both normal in the impedance tube and grazing incidence in the flow duct. The performance of plasma-based active absorber is competitive with conventional passive technologies in terms of effective absorption bandwidth and low-frequency operation, however, it presents some inherent limitations that are discussed. The study reveals that the corona discharge technology is suitable for active noise control in ducts while offering flexibility in design, compactness, and versatility of the absorption frequency range.

physics.app-ph↗

PID-like active control strategy for electroacoustic resonators to design tunable single-degree-of-freedom sound absorbers

Sound absorption at low frequencies still remains a challenge in both scientific research and engineering practice. Natural porous materials are ineffective in this frequency range, as well as acoustic resonators which present too narrow bandwidth of absorption, thus requiring alternative solutions based on active absorption techniques. In the present work, we propose an active control framework applied on a closed-box loudspeaker to enable the adjustment of the acoustic impedance at the loudspeaker diaphragm. More specifically, based on the proportionality between the pressure inside the enclosure and the axial displacement of the loudspeaker diaphragm at low frequencies, we demonstrate both analytically and experimentally that a PID-like feedback control approach allows tuning independently the compliance, the resistance and the moving mass of the closed-box loudspeaker to implement a prescribed impedance of a single-degree-of-freedom resonator. By considering different control combinations to tailor the resonator characteristics, a perfect absorption (with absorption coefficient equal to 1) is achievable at the target resonance frequency, while enlarging the effective absorption bandwidth. Moreover, the proposed feedback control strategy shows an excellent control accuracy, especially compared to the feedforward-based control formerly reported in the literature. The mismatches between the performance of experimental prototype and the model, likely to result from the control time delay and the inaccuracy in estimating the loudspeaker parameters, can be compensated directly by tuning the control parameters in the control platform. The active resonators implemented through the reported control scheme can be used to build more complex acoustic devices/structures to enable high-efficiency broadband sound absorption or other types of acoustic phenomena such as wavefront shaping.

physics.app-ph↗

Improving sound absorption through nonlinear active electroacoustic resonators

Absorbing airborne noise at frequencies below 300 Hz is a particularly vexing problem due to the absence of natural sound absorbing materials at these frequencies. The prevailing solution for low-frequency sound absorption is the use of passive narrow-band resonators, whose absorption level and bandwidth can be further enhanced using nonlinear effects. However, these effects are typically triggered at high intensity levels, without much control over the form of the nonlinear absorption mechanism. In this study, we propose, implement, and experimentally demonstrate a nonlinear active control framework on an electroacoustic resonator prototype, allowing for unprecedented control over the form of non-linearity, and arbitrarily low sound intensity thresholds. More specifically, the proposed architecture combines a linear feedforward control on the front pressure through a first microphone located at the front face of the loudspeaker, and a nonlinear feedback on the membrane displacement estimated through the measurement of the pressure inside the back cavity with a second microphone located in the enclosure. It is experimentally shown that even at a weak excitation level, it is possible to observe and control the nonlinear behaviour of the system. Taking the cubic nonlinearity as an example, we demonstrate numerically and experimentally that in the low frequency range ([50 Hz, 500 Hz]), the nonlinear control law allows improving the sound absorption performance, i.e. enlarging the bandwidth of optimal sound absorption while increasing the maximal absorption coefficient value, and producing only a negligible amount of nonlinear distortion. The reported experimental methodology can be extended to implement various types of hybrid linear and/or nonlinear controls, thus opening new avenues for managing wave nonlinearity and achieving non-trivial wave phenomena.

physics.app-ph↗

Constant-pressure sound waves in non-Hermitian disordered media

When waves impinge on a disordered material they are back-scattered and form a highly complex interference pattern. Suppressing any such distortions in the free propagation of a wave is a challenging task with many applications in a number of different disciplines. In a recent theoretical proposal, it was pointed out that both perfect transmission through disorder as well as a complete suppression of any variation in a wave intensity can be achieved by adding a continuous gain-loss distribution to the disorder. Here we show that this abstract concept can be implemented in a realistic acoustic system. Our prototype consists of an acoustic waveguide containing several inclusions that scatter the incoming wave in a passive configuration and provide the gain or loss when being actively controlled. Our measurements on this non-Hermitian acoustic metamaterial demonstrate unambiguously the creation of a reflectionless scattering wave state that features a unique form of discrete constant-amplitude pressure waves. In addition to demonstrating that gain-loss additions can turn localised systems into transparent ones, we expect our proof-of-principle demonstration to trigger interesting new developments not only in sound engineering, but also in other related fields such as in non-Hermitian photonics.

physics.app-ph↗

Joint Estimation of Room Geometry and Modes with Compressed Sensing

Acoustical behavior of a room for a given position of microphone and sound source is usually described using the room impulse response. If we rely on the standard uniform sampling, the estimation of room impulse response for arbitrary positions in the room requires a large number of measurements. In order to lower the required sampling rate, some solutions have emerged that exploit the sparse representation of the room wavefield in the terms of plane waves in the low-frequency domain. The plane wave representation has a simple form in rectangular rooms. In our solution, we observe the basic axial modes of the wave vector grid for extraction of the room geometry and then we propagate the knowledge to higher order modes out of the low-pass version of the measurements. Estimation of the approximate structure of the $k$-space should lead to the reduction in the terms of number of required measurements and in the increase of the speed of the reconstruction without great losses of quality.

eess.AS↗