arXiv subjects

Oded Zilberberg

Publications and source records attributed to Oded Zilberberg.

At least 37 records · Page 2Linked to original sources

arXiv2025

Observing Laughlin's pump using quantized edge states in graphene

Laughlin's thought experiment of quantized charge pumping is central to understanding the integer quantum Hall effect (IQHE) and the topological origin of its conductance quantization. Its direct experimental observation, however, has been hindered by the difficulty of realizing clean electronic edges. We address this by fabricating ultra-small, lithographically defined contacts on graphene. This creates a Corbino-equivalent system, with well-confined inner edge states. Crucially, the small contact size induces strong energy quantization of the edge states. This quantization allows us to directly resolve the spectral flow associated with Laughlin's pump. By tracing the finite-size resonances of the inner edge, we observe clear oscillations in conductance as a function of magnetic field and carrier density. The oscillation period scales with contact size, consistent with quantized charge transfer. Thus, our results provide a direct observation of the spectral flow underlying Laughlin's pump. The simplicity of the graphene platform makes this approach scalable and robust for exploring fundamental topological effects.

cond-mat.mes-hall↗

arXiv2025

Ultrafast Non-Hermitian Skin Effect

Topological phases of matter commonly feature protected states at their boundaries. Transferring this protection to time-metamaterials is extremely challenging, as it requires the generation of an abrupt interface between two topologically distinct bulks. Here, we realize and measure an ultrafast topological non-Hermitian skin mode bound to an interface circulating within the cavity of a fast-gain semiconductor laser. The nonlinear stationary state generated in such devices features a jump in the instantaneous frequency. We show that this discontinuity gives rise to a topological interface for the field fluctuations in the system. Using direct intensity sampling, we experimentally measure the skin modes and their positioning at the frequency jump of the stationary state. Analysis of these isolated modes reveals an ultrashort full-width at half-maximum of 583 $\pm$ 16 fs. Furthermore, we show that we can tune the shape and relative timing shift of the skin modes via external bias modulation. Finally, both numerical and experimental analysis of the noise in the system reveal that field fluctuations are funneled into the topological interface. Our findings reveal a new way to generate topologically protected states of light in time, which paves the way for novel time-varying physics as well as metrological applications.

physics.optics↗

arXiv2025

Non-Hermitian topology and skin modes in the continuum via parametric processes

We demonstrate that Hermitian, nonlocal parametric pairing processes can induce non-Hermitian topology and skin modes, offering a simple alternative to complex bath engineering. Our model, stabilized by local dissipation and operating in the continuum limit, reveals exceptional points that spawn a tilted diabolical line in the dispersion. Local dissipation prevents instabilities, while a bulk anomaly signals unscreened current response. Upon opening the boundaries, we observe a non-Hermitian skin effect with localized edge modes. Through bulk winding indices and non-Bloch theory, we establish a robust bulk-boundary correspondence, highlighting parametric drives as a scalable route to non-Hermitian topology in bosonic systems.

cond-mat.mes-hall↗

arXiv2025

The parametric instability landscape of coupled Kerr parametric oscillators

Networks of coupled Kerr parametric oscillators (KPOs) hold promise as for the realization of neuromorphic and quantum computation. Yet, their rich bifurcation structure remains largely not understood. Here, we employ secular perturbation theory to map the stability regions of these networks, and identify the regime where the system can be mapped to an Ising model. Starting with two coupled KPOs, we show how the bifurcations arise from the competition between the global parametric drive and linear coupling between the KPOs. We then extend this framework to larger networks with all-to-all equal coupling, deriving analytical expressions for the full cascade of bifurcation transitions. In the thermodynamic limit, we find that these transitions become uniformly spaced, leading to a highly regular structure. Our results reveal the precise bounds under which KPO networks have an Ising-like solution space, and thus provides crucial guidance for their experimental implementation.

cond-mat.mes-hall↗

arXiv2024

Aharonov-Bohm interferometer in inverted-band pn junctions

Inverted-band $pn$ junctions in two-dimensional materials offer a promising platform for electron optics in condensed matter, as they allow to manipulate and guide electron beams without the need for spatial confinement. In this work, we propose the realization of an Aharonov-Bohm (AB) interferometer using such $pn$ junctions. We observe AB oscillations in numerically obtained conductance and analytically identify the conditions for their appearance by analyzing the scattering processes at the $pn$ interface. To support experimental implementation, we also consider junctions with a graded interface, where the potential varies smoothly between the $p$- and $n$-doped regions. Our results reveal an abrupt change in the AB-oscillation frequency, which we attribute to a distinct transition in the hybridization across the interface. We verify that our reported AB oscillations are robust to realistic disorder and temperature decoherence channels. Our study paves the way for realizing the Aharonov-Bohm effect in bulk mesoscopic systems without the need for external spatial confinement, offering new possibilities in electron optics.

cond-mat.mes-hall↗

arXiv2024

Fluctuation instabilities via internal resonance in a multimode membrane as a mechanism for frequency combs

We explore self-induced parametric coupling, also called internal resonances (IRs), in a membrane nanoelectromechanical system. Specifically, we focus on the formation of a limit cycle manifesting as a phononic frequency comb. Utilizing a pump-noisy-probe technique and theoretical modeling, we reveal the behavior of mechanical excitations revealing themselves as sidebands of the stationary IR response. We find that when the energy-absorbing excitation of a lower mode is parametrically-upconverted to hybridize with a higher mode, significant squeezing and bimodality in the upper mode occurs. Instead, when the upconverted absorbing excitation hybridizes with an emitting sideband of the higher mode, a Hopf bifurcation occurs and a limit cycle forms, manifesting as a frequency comb. We thus reveal a unique mechanism to obtain frequency combs in parametrically-coupled modes. We furthermore demonstrate a rich variety of IR effects, the origin of which significantly extends beyond standard linear parametric coupling phenomena. Our findings enhance the understanding of energy transfer mechanisms with implications for advanced sensing technologies and novel phononic metamaterials.

cond-mat.mes-hall↗

arXiv2024

Effect of the readout efficiency of quantum measurement on the system entanglement

Monitored quantum systems evolve along stochastic trajectories correlated with the observer's knowledge of the system's state. Under such dynamics, certain quantum resources like entanglement may depend on the observer's state of knowledge. Here, we quantify the entanglement for a particle on a 1d quantum random walk under inefficient monitoring using a mixed state-entanglement measure - the configuration coherence. We find that the system's maximal mean entanglement at the measurement-induced quantum-to-classical crossover is suppressed in different ways by the measurement strength and inefficiency. In principle, strong measurements can lower the amount of entanglement indefinitely. However, at a given measurement strength, efficient readout can crucially increase the system entanglement, making high-fidelity detectors essential for successful quantum computing. Our results bear impact for a broad range of fields, ranging from quantum simulation platforms of random walks to questions related to measurement-induced phase transitions.

quant-ph↗

arXiv2024

Emergent cavity junction around metal-on-graphene contacts

Harnessing graphene devices for applications relies on a comprehensive understanding of how to interact with them. Specifically, scattering processes at the interface with metallic contacts can induce reproducible abnormalities in measurements. Here, we report on emergent transport signatures appearing when contacting sub-micrometer high-quality metallic top contacts to graphene. Using electrostatic simulations and first-principle calculations, we reveal their origin: the contact induces an n-doped radial cavity around it, which is cooperatively defined by the metal-induced electrostatic potential and Klein tunneling. This intricate mechanism leads to secondary resistance peaks as a function of graphene doping that decreases with increasing contact size. Interestingly, in the presence of a perpendicular magnetic field, the cavity spawns a distinct set of Landau levels that interferes with the Landau fan emanating from the graphene bulk. Essentially, an emergent 'second bulk' forms around the contact, as a result of the interplay between the magnetic field and the contact-induced electrostatic potential. The interplay between the intrinsic and emergent bulks leads to direct observation of bulk-boundary correspondence in our experiments. Our work unveils the microscopic mechanisms manifesting at metal-graphene interfaces, opening new avenues for understanding and devising graphene-based electronic devices.

cond-mat.mes-hall↗

arXiv2024

A soft-clamped topological waveguide for phonons

Topological insulators were originally discovered for electron waves in condensed matter systems. Recently this concept has been transferred to bosonic systems such as photons and phonons, which propagate in materials patterned with artificial lattices that emulate spin-Hall physics. This work has been motivated, in part, by the prospect of topologically protected transport along edge channels in on-chip circuits. Importantly, even in principle, topology protects propagation against backscattering, but not against loss, which has remained limited to the dB/cm-level for phonon waveguides, be they topological or not. Here, we combine advanced dissipation engineering, in particular the recently introduced method of soft-clamping, with the concept of a valley-Hall topological insulator for phonons. This enables on-chip phononic waveguides with propagation losses of 3 dB/km at room temperature, orders of magnitude below any previous chip-scale devices. For the first time, the low losses also allow us to accurately quantify backscattering protection in a topological phonon waveguide, using high-resolution ultrasound spectroscopy. We infer that phonons follow a sharp, 120 degree-bend with a 99.99%-probability instead of being scattered back, and less than one phonon in a million is lost. The extraordinary combination of features of this novel platform suggest applications in classical and quantum signal routing, processing, and storage.

cond-mat.mes-hall↗

arXiv2024

Scrambling-induced entanglement suppression in noisy quantum circuits

Quantum information scrambling is a process happening during thermalization in quantum systems and describes the delocalization of quantum information. It is closely tied to entanglement, a key resource for quantum technologies and an order parameter for quantum many-body phenomena. We investigate the effect of dephasing noise on a multi-qubit teleportation protocol that experimentally validated quantum information scrambling. We find that while scrambling enhances information distribution, it is highly noise-sensitive, leading to decreased teleportation fidelity and an increase in the classical mixing of the quantum state. Using negativity as a mixed-state entanglement measure, we identify two fundamentally different entanglement-scaling regimes: efficient entanglement generation under weak dephasing noise, and entanglement suppression under strong dephasing noise. We show that in the latter, the teleportation consumes more entanglement than the scrambling is able to create. Comparison with a SWAP-gate-based teleportation protocol confirms that the entanglement suppression is a consequence of the scrambling mechanism. Our findings suggest that the information dynamics during thermalization is critically affected by dephasing noise, and confirm that in present-day noisy quantum devices, local information exchange is preferable over long-range information scrambling.

quant-ph↗

arXiv2024

Topological classification of driven-dissipative nonlinear systems

In topology, one averages over local geometrical details to reveal robust global features. This approach proves crucial for understanding quantized bulk transport and exotic boundary effects of linear wave propagation in (meta-)materials. Moving beyond linear Hamiltonian systems, the study of topology in physics strives to characterize open (non-Hermitian) and interacting systems. Here, we establish a framework for the topological classification of driven-dissipative nonlinear systems. Specifically, we define a graph index for the Floquet semiclassical equations of motion describing such systems. The graph index builds upon topological vector analysis theory and combines knowledge of the particle-hole nature of fluctuations around each out-of-equilibrium stationary state. To test this approach, we divulge the topological invariants arising in a micro-electromechanical nonlinear resonator subject to forcing and a time-modulated potential. Our framework classifies the complete phase diagram of the system and reveals the topological origin of driven-dissipative phase transitions, as well as that of under- to over-damped responses. Furthermore, we predict topological phase transitions between symmetry-broken phases that pertain to population inversion transitions. This rich manifesting phenomenology reveals the pervasive link between topology and nonlinear dynamics, with broad implications for all fields of science.

cond-mat.mes-hall↗

arXiv2024

Quench dynamics of Wannier-Stark states in an active synthetic photonic lattice

Photonic emulators have facilitated the investigation of numerous solid-state phenomena and have contributed to the development of optical devices inspired by quantum mechanics. Although current photonic emulators are constrained to bosonic behavior with local interactions, the utilization of active synthetic lattices holds promise for surpassing these limitations. In this study, we propose employing the modulated ring fast-gain laser as a foundation for emulating quench dynamics within a synthetic lattice that conforms to equal density filling of its reciprocal space. To illustrate the effectiveness of this emulation platform, we subject a dispersed Wannier-Stark ladder to quenching and directly observe oscillations, enabled by the fast-gain, along with their coherent stabilization to a single Wannier stark state. These coherent dynamics stem directly from our lasers liquid state of light, a characteristic resulting from fast-gain and explained by the rapid decay of fluctuations occurring on the system's shortest timescale. Additionally, by adequately biasing the lattice through detuning the modulation from the cavity resonance, this process supports oscillatory dynamics within the synthetic space.

physics.optics↗

arXiv2024

Floquet expansion by counting pump photons

Periodically-driven systems engender a rich competition between the time scales of the drives and those of the system, leading to a limited ability to describe the system in full. We present a framework for the description of interacting bosonic driven systems via a Floquet expansion on top of a quantization that "counts" the drive photons, and provide compelling arguments for the superior performance of our method relative to standard Floquet approaches. Crucially, our approach extends beyond the rotating wave approximation and addresses the long-standing issue of mismatch between the quantum Floquet formalism and its classical counterpart. We, furthermore, pinpoint key corrections to the positions of multiphoton resonances, which are commonly used in the calibration and operation of qubit architectures.

quant-ph↗

arXiv2024

Band engineering and study of disorder using topology in compact high kinetic inductance cavity arrays

Superconducting microwave metamaterials offer enormous potential for quantum optics and information science, enabling the development of advanced quantum technologies for sensing and amplification. In the context of circuit quantum electrodynamics, such metamaterials can be implemented as coupled cavity arrays (CCAs). In the continuous effort to miniaturize quantum devices for increasing scalability, minimizing the footprint of CCAs while preserving low disorder becomes paramount. In this work, we present a compact CCA architecture leveraging superconducting NbN thin films presenting high kinetic inductance, which enables high-impedance CCA ($\sim1.5$ k$Ω$), while reducing the resonator footprint. We demonstrate its versatility and scalability by engineering one-dimensional CCAs with up to 100 resonators and exhibiting multiple bandgaps. Additionally, we quantitatively investigate disorder in the CCAs using symmetry-protected topological SSH modes, from which we extract a resonator frequency scattering of $0.22^{+0.04}_{-0.03}\%$. Our platform opens up exciting new prospects for analog quantum simulations of many-body physics with ultrastrongly coupled emitters.

quant-ph↗

arXiv2024

Tomasch Oscillations as Above-Gap Signature of Topological Superconductivity

The identification of topological superconductors usually involves searching for in-gap modes that are protected by topology. However, in the current experimental settings, the smoking-gun evidence of these in-gap modes is still lacking. In this work, we propose to distinguish between two-dimensional conventional s-wave and topological p-wave superconductors by above-gap transport signatures. Our method utilizes the emergence of Tomasch oscillations of quasiparticles in a junction consisting of a superconductor sandwiched between two metallic leads. We demonstrate that the behavior of the oscillations in conductance as a function of the interface barriers provides a distinctive signature for s-wave and p-wave superconductors. Specifically, the oscillations become weaker as the barrier strength increases in s-wave superconductors, while they become more pronounced in p-wave superconductors, which we prove to be a direct manifestation of the pairing symmetries. Our method opens a new route for identifying topological superconductors through above-gap transport.

cond-mat.supr-con↗

arXiv2024

Electron-optics using negative refraction in two-dimensional inverted-band $pn$ junctions

Electron optics deals with condensed matter platforms for manipulating and guiding electron beams with high efficiency and robustness. Common devices rely on the spatial confinement of the electrons into one-dimensional channels. Recently, there is growing interest in electron optics applications in two dimensions, which heretofore are almost exclusively based on graphene devices. In this work, we study band-inverted systems resulting from particle-hole hybridization and demonstrate their potential for electron optics applications. We develop the theory of interface scattering in an inverted-band $pn$ junction using a scattering matrix formalism and observe negative refraction conditions as well as transmission filtering akin to graphene's Klein tunneling but at finite angles. Based on these findings, we provide a comprehensive protocol for constructing electron optic components, such as focusing and bifurcating lenses, polarizers, and mirrors. We numerically test the robustness of our designs to disorder and finite temperatures, and motivate the feasibility of experimental realization. Our work opens avenues for electron optics in two dimensions beyond graphene-based devices, where a plethora of inverted-band materials in contemporary experiments can be harnessed.

cond-mat.mes-hall↗

arXiv2024

Hamiltonian reconstruction via ringdown dynamics

Many experimental techniques aim at determining the Hamiltonian of a given system. The Hamiltonian describes the system's evolution in the absence of dissipation, and is often central to control or interpret an experiment. Here, we theoretically propose and experimentally demonstrate a method for Hamiltonian reconstruction from measurements over a large area of phase space, overcoming the main limitation of previous techniques. A crucial ingredient for our method is the presence of dissipation, which enables sampling of the Hamiltonian through ringdown-type measurements. We apply the method to a driven-dissipative system -- a parametric oscillator -- observed in a rotating frame, and reconstruct the (quasi-)Hamiltonian of the system. Furthermore, we demonstrate that our method provides direct experimental access to the so-called symplectic norm of the stationary states of the system, which is tied to the particle- or hole-like nature of excitations of these states. In this way, we establish a method to unveil qualitative differences between the fluctuations around stabilized minima and maxima of the nonlinear out-of-equilibrium stationary states. Our method constitutes a versatile approach to characterize a wide class of driven-dissipative systems.

cond-mat.mes-hall↗

arXiv2023

Quantifying measurement-induced quantum-to-classical crossover using an open-system entanglement measure

The evolution of a quantum system subject to measurements can be described by stochastic quantum trajectories of pure states. Instead, the ensemble average over trajectories is a mixed state evolving via a master equation. Both descriptions lead to the same expectation values for linear observables. Recently, there is growing interest in the average entanglement appearing during quantum trajectories. The entanglement is a nonlinear observable that is sensitive to so-called measurement-induced phase transitions, namely, transitions from a system-size dependent phase to a quantum Zeno phase with area-law entanglement. Intriguingly, the mixed steady-state description of these systems is insensitive to this phase transition. Together with the difficulty of quantifying the mixed state entanglement, this favors quantum trajectories for the description of the quantum measurement process. Here, we study the entanglement of a single particle under continuous measurements (using the newly developed configuration coherence) in both the mixed state and the quantum trajectories descriptions. In both descriptions, we find that the entanglement at intermediate time scales shows the same qualitative behavior as a function of the measurement strength. The entanglement engenders a notion of coherence length, whose dependence on the measurement strength is explained by a cascade of underdamped-to-overdamped transitions. This demonstrates that measurement-induced entanglement dynamics can be captured by mixed states.

quant-ph↗