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

The quantum world obeys principles that confound classical intuition, none more so than Heisenberg’s uncertainty principle. It reveals a fundamental limit to simultaneously knowing a particle’s exact position and momentum, painting the quantum dance as inherently uncertain. Yet, beneath this veil, atoms in molecules engage in synchronous vibrations, rigidly structured and forever oscillating—even at absolute zero temperature where classical physics predicts stillness. This perpetual ‘dance’ is sustained by zero-point energy, a purely quantum mechanical phenomenon signifying the lowest possible energy state of a system.

Historically, these subtle zero-point motions were accessible only through indirect inference or theoretical models. Direct measurement, particularly of correlated vibrations among atoms, has remained out of reach due to the ephemeral and complex nature of quantum excitations. However, the recent work by Professor Till Jahnke and colleagues at Goethe University Frankfurt, facilitated by sophisticated experimental setups at European XFEL, has directly observed these covert vibrational patterns within single molecules of iodopyridine, a medium-sized organic compound comprised of eleven atoms with twenty-seven vibrational modes. These modes manifest as collective oscillations, akin to an ensemble performing a multifaceted choreography — from delicate ballet-like vibrations to energetic tango rhythms.

The experimental breakthrough hinged on advances in Coulomb Explosion Imaging (CEI), an innovative technique that ‘freezes’ the molecular positions instantaneously by triggering a controlled Coulomb explosion. Here, ultrashort, immensely intense high-frequency X-ray laser pulses strip numerous electrons from the molecule, causing the positively charged atomic fragments to violently repel each other. This rapid disintegration, occurring on timescales of a few hundred attoseconds, essentially captures a snapshot of the original molecular structure and atomic positions with sub-angstrom accuracy.

This atomic ‘explosion’ is meticulously recorded by a sophisticated apparatus known as a COLTRIMS (Cold Target Recoil Ion Momentum Spectroscopy) reaction microscope. The bespoke COLTRIMS system used was tailored specifically for the European XFEL by Dr. Gregor Kastirke during his doctoral research at Goethe University, showcasing decades of technical refinement. The setup measures the precise times and positions at which fragment ions strike detectors, enabling the reconstruction of their initial momentum vectors. These data allow scientists to backtrack and visualize the intricate web of atomic positions—and thus the vibrational modes—within the intact molecule before fragmentation.

Professor Jahnke emphasizes the novelty of observing coupled atomic vibrations: “Atoms do not vibrate simply in isolation but in correlated patterns. Our results represent the first direct measurement of such correlated zero-point motion in individual complex molecules within their quantum ground state.” Until now, vibrational mode analysis predominantly relied on spectroscopic techniques that infer average properties of ensembles over time. This study pioneers direct, molecule-resolved snapshots of quantum fluctuations, advancing beyond mere inference to direct, real-space imagery of nuclear quantum dynamics.

Notably, the data used for this discovery emerged serendipitously from earlier measurement campaigns in 2019, originally designed for different scientific purposes. It took a concerted interdisciplinary collaboration, particularly with theoretical physicists at the Center for Free-Electron Laser Science in Hamburg, to develop novel analytic methods and unlock the quantum signatures buried within the dataset. Benoît Richard and Ludger Inhester played key roles in refining these methodologies, demonstrating the indispensability of cross-disciplinary synergy in solving complex scientific puzzles.

Beyond the foundational quantum insight, this experimental approach carries profound implications for chemical physics and quantum chemistry. By unveiling the real-time motion and correlation of atoms at the quantum limit, it opens avenues for controlled manipulation of molecular dynamics and chemical reactivity. This method promises to deepen our understanding of phenomena like quantum tunneling, vibrational energy transfer, and reaction mechanisms at their most fundamental level.

Looking ahead, the researchers aspire to extend these techniques from atomic nuclei to electron dynamics within molecules. The electron motion is even swifter and intricately coupled to nuclear vibrations, forming a dual choreography essential to all molecular processes such as photoexcitation and energy conversion. “Our vision is to create genuine molecular movies,” Jahnke explains, “capturing not only the dance of atoms but also the dance of electrons—with temporal resolution sufficient to resolve their interdependent quantum motions.”

Such capabilities could revolutionize fields ranging from molecular electronics to quantum information science, where controlling quantum states with exquisite precision is paramount. The Frankfurt-developed COLTRIMS method, combined with powerful free-electron laser sources, provides a powerful platform to probe and ultimately manipulate the fundamental quantum nature of matter.

This remarkable scientific journey underscores the power of combining cutting-edge lasers, state-of-the-art detectors, and theoretical innovation to directly probe phenomena once thought intangible. As the convergence of experimental finesse and quantum theory accelerates, we stand on the threshold of transforming our grasp of the molecular quantum world from abstract principle into vivid visualization. The dance of atoms, once hidden in shadows, has now been illuminated in dazzling clarity.

Subject of Research: Not applicable
Article Title: Imaging collective quantum fluctuations of the structure of a complex molecule
News Publication Date: 7-Aug-2025
Web References: http://dx.doi.org/10.1126/science.adu2637
Image Credits: Till Jahnke / Goethe University Frankfurt

Keywords

Quantum fluctuations, zero-point motion, Coulomb Explosion Imaging, COLTRIMS, European XFEL, molecular vibrations, quantum choreography, quantum ground state, atomic physics, ultrafast X-ray laser, molecular dynamics, quantum molecular imaging