The work, led by Svetlana Malinovskaya, professor at the Charles V. Schaefer, Jr. School of Engineering and Science at Stevens, addresses a problem that has long plagued experimentalists working at the frontier of quantum control. “A laser is a device that creates a very narrow, highly directional beam of light,” Malinovskaya explains. “Unlike sunlight or light from regular bulbs or flashlights that scatters in all directions, a laser produces light in which all waves move together in a highly synchronized way allowing the light to be very focused and controlled with remarkable precision.”

When such a light wave reaches a quantum system, its packets of energy, called photons, are absorbed by the atoms and molecules in that system, lifting them into higher-energy states. This is precisely the mechanism by which scientists manipulate quantum behavior. But there is a catch. If the laser field is too intense, a single atom or molecule may interact with several photons at once. These simultaneous interactions, known as multiphoton processes, open additional pathways between the system’s energy levels, scrambling the intended dynamics and rendering the quantum system difficult, sometimes impossible, to predict or control.

“By shining laser light on molecules, we can excite molecular vibrations in a controlled way and learn about molecular properties,” says Malinovskaya. “But when very strong laser fields are used for precise quantum control, they can also trigger unwanted multiphoton processes allowing the molecule to access many different states and pathways, making its behavior much more difficult to predict and control.” In other words, the instrument of control becomes an instrument of chaos, and the very act of measurement or manipulation contaminates the result.

That unpredictability is more than an inconvenience; it is a roadblock for the technologies hoping to capitalize on quantum mechanics. “That’s not what we need, particularly for the precision measurements required in quantum computing or quantum sensing,” Malinovskaya says. “In those systems, every photon counts.” Quantum computers rely on the faithful preparation and manipulation of quantum states to perform calculations, while quantum sensors extract exquisitely faint signals from their environment, and even a small number of stray photon interactions can corrupt a computation or drown a measurement in noise. The ideal solution would use just enough light to steer a quantum system where it needs to go, without any excess energy spilling over into unwanted channels.

In their new study, Malinovskaya and her collaborators propose to do exactly that with what they describe as a “digitized” laser pulse. Their calculations show that a train of twelve short, low-intensity laser pulses can produce the same net effect on a quantum system as one long, intense pulse, but without pushing the atoms or molecules into the undesirable states that plague high-intensity approaches. The idea is conceptually similar to replacing a single powerful hammer blow with a rapid series of precisely timed taps that, together, accomplish the same task with far less collateral disturbance.

“Instead of using one very strong laser pulse, we suggest mimicking its effects with a carefully programmed sequence—or train—of weak pulses,” Malinovskaya explains. “Each pulse carries much less energy, but its timing, intensity, frequency and phase are precisely calculated and controlled.” According to the team’s analysis, this sequence of gentle nudges can drive the same gradual transfer of a quantum system from one state to another that a much stronger pulse would produce. The desired outcome is preserved, while the laser intensity at each step remains low enough to keep multiphoton processes from ever gaining a foothold.

The method is an outgrowth of a well-established control strategy known as adiabatic passage, in which a quantum system is guided slowly and smoothly between energy states so that it remains stable against small imperfections. By digitizing that smooth evolution into discrete steps, the researchers retain the robustness of the adiabatic approach while shedding its traditional dependence on high peak laser intensities. The result, described in a paper titled “Digitizing ultrafast adiabatic passage with a pulse train” published in the Journal of the Optical Society of America B on September 10, 2026, offers a theoretical blueprint that, if borne out experimentally, could reshape how quantum control experiments are designed across a wide range of platforms.

The potential applications stretch across the quantum technology landscape. Quantum sensors, quantum computers and quantum simulators all depend on reliable preparation and manipulation of quantum states, and the pulse-train technique could make those operations more accurate and repeatable. In molecular physics and spectroscopy, where intense laser pulses often generate background effects that interfere with measurements, the lower-intensity approach could yield cleaner data and sharper insights into molecular structure and behavior. The implications extend beyond physics laboratories as well: in biology and medicine, laser-based technologies are widely used for imaging and disease diagnosis, and reducing pulse intensity offers a straightforward way to minimize damage to sensitive cells and tissues, opening a path to safer optical diagnostics and therapies.

For now, the technique remains theoretical, but the paper lays out all of the necessary calculations in full detail, providing experimenters with a concrete roadmap. “The next step will be to actually test it,” Malinovskaya says. “When demonstrated experimentally, this approach will open a new way to precisely control quantum systems with weaker laser fields, making it easier to use in practical applications.” If the laboratory results match the theory, the digitized pulse train could become a standard tool in the quantum engineer’s kit, helping to bring the promise of quantum technologies—from unimaginably powerful computers to sensors capable of detecting the faintest whispers of nature—closer to everyday reality, one carefully timed pulse at a time.

Subject of Research: Digitized ultrafast adiabatic passage using low-intensity laser pulse trains for precise quantum state control

Article Title: Stevens researchers take step toward more precise, practical quantum technologies

Article References: Stevens researchers take step toward more precise, practical quantum technologies. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: quantum control, laser pulses, multiphoton processes, adiabatic passage, quantum computing, quantum sensing, spectroscopy, molecular physics, quantum states, biomedical imaging, Stevens Institute of Technology, Svetlana Malinovskaya

Historically, physicists have categorized the ways quantum waves or particles occupy materials into two distinct types: localized modes, where energy remains confined to a small region due to barriers or defects, and propagating waves, which travel freely across the material. The localized modes exhibit rapid exponential decay, meaning their influence vanishes quickly outside a limited zone, while propagating waves show no decay at all and carry energy across long distances. Between these two extremes, theorists postulated the existence of intermediate states exhibiting a slower algebraic, or power-law, decay, but these were thought to be rare phenomena requiring delicate tuning.

The new research challenges this narrative by demonstrating that power-law skin modes—formerly regarded as esoteric exceptions—are in fact abundantly realized when moving beyond traditional one-dimensional models into the richer, more complex terrain of two or higher-dimensional systems. By expanding the conceptual framework, Sun and his collaborators showed that these modes naturally arise along the boundaries or “skin” of materials in a robust manner, unaffected by minor perturbations or imperfections that would typically suppress such states.

From a mathematical perspective, the distinction between exponential and power-law decay lies in the rate at which the amplitude of the quantum state diminishes with distance. Exponential decay plummets sharply, often making localized states highly sensitive to environmental noise or structural variations. Power-law decay, while slower, still restricts energy spread but does so in a way that effectively balances confinement with extended reach. This subtle but profound difference implies that information or energy can propagate partially across the system while retaining localized features, a property with direct implications for next-generation devices.

One of the most striking findings in the study is the critical role of a material’s geometry—specifically its aspect ratio—in shaping the behavior of these power-law skin modes. Unlike previous models that treated boundaries as uniform or one-dimensional edges, the team’s exploration of two-dimensional shapes revealed that the spatial configuration dramatically influences mode distribution and decay patterns. Such sensitivity to shape paves the way for engineered materials where quantum states can be precisely tailored by geometry alone, without resorting to cumbersome fine-tuning of material parameters or external fields.

The discovery stands to impact quantum computing fundamentally. Quantum bits, or qubits, which can exist in complex superpositions of states, require delicate management of coherence and information flow. The newfound robustness of power-law modes suggests qubits may simultaneously host strongly localized modes for stable computation and power-law modes that transmit quantum information efficiently across a device. This duality could overcome some of the intractable challenges faced by present-day quantum architectures, offering a fresh design paradigm inspired directly by these newly elucidated physical principles.

Professor Sun describes the research as an exciting confluence of foundational physics and practical opportunity. “This work reveals novel concepts on the fundamental side, while also opening new opportunities for future applications,” he stated. Unlike many breakthroughs rooted in abstract theory but distant from implementation, the firm mathematical footing and experimental relevance of these modes make them immediately compelling for exploration in quantum materials, photonics, and beyond.

Underlying this advance is a reconsideration of the “non-Hermitian skin effect,” a counterintuitive phenomenon where certain open quantum systems exhibit an accumulation of states along material edges, defying the traditional bulk-boundary correspondence. The new algebraic approach generalizes this effect across arbitrary dimensions and connects it to a broadened Fermi surface formula—a pivotal tool in quantum theory that relates the geometry of electron states to their physical properties. Sun and colleagues’ method provides a unifying framework that bridges previously disparate observations and theoretical models.

At its core, the research exemplifies how expanding dimensionality in quantum models can unlock behaviors impossible to capture in simpler, one-dimensional analogies. The familiar rubber-band analogy, often used to illustrate localized versus traveling waves, falls short when confronted with higher-dimensional lattice structures and complex boundary conditions. By accounting for these richer geometries, the team unveiled a landscape where power-law decays are not only widespread but also definitional of the system’s fundamental physics.

Overcoming traditional limitations, the study also underscores computational and experimental feasibility. Because the discovered power-law modes are extremely robust and do not require fine-tuning, they are more likely to be observed and manipulated in real laboratory settings. This robustness contrasts sharply with delicate quantum states that collapse under minor environmental disturbances, thus raising hopes for practical realization in solid-state platforms or photonic simulators.

Looking ahead, the implications extend far beyond academic curiosity. Quantum materials exploiting algebraic non-Hermitian skin effects could usher in new classes of devices leveraging semi-localized states for enhanced control of light, sound, or electronic signals. Precision shaping of device geometry could tailor performance characteristics, offering a versatile toolkit for engineers and physicists alike.

The study, published in the prestigious journal Physical Review X, was partly funded by the Office of Naval Research, highlighting the strategic interest in exploring fundamental quantum phenomena with potential defense and technological applications. Key contributors besides Professor Sun include research fellow Kai Zhang and graduate student Chang Shu, whose efforts helped deepen and extend the theoretical framework.

Ultimately, this remarkable investigation opens a new frontier in quantum physics by demonstrating that once-elusive power-law skin modes are both universal and tunable features of materials in higher dimensions. By blending mathematical sophistication with visionary physical insight, the research redefines what quantum systems can do and sets the stage for innovations that harness the subtle interplay between localization, propagation, and geometry at the quantum frontier.

Subject of Research: Quantum semi-localized states and power-law skin modes in higher-dimensional non-Hermitian systems

Article Title: Algebraic Non-Hermitian Skin Effect and Generalized Fermi Surface Formula in Arbitrary Dimensions

News Publication Date: 11-Aug-2025

Web References: 10.1103/cwwd-bclc

Image Credits: Credit: K. Zhang et al. Phys. Rev. X. 2025 (DOI: 10.1103/cwwd-bclc) Used under a CC-BY license.

Keywords

quantum mechanics, non-Hermitian physics, power-law decay, localization, quantum computing, skin effect, algebraic modes, higher dimensions, quantum materials, boundary phenomena, Fermi surface, quantum technologies