This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Quantum technologies are poised to transform fields ranging from medicine and sensing to computing and communications by manipulating the energy states of atoms and molecules. These manipulations are achieved by controlling quantum states with laser pulses.
However, the intense laser fields often required for this control can cause unwanted effects that disrupt the very system they aim to manipulate. Now, Stevens researchers and their collaborators have developed a novel method that enables precise control of quantum systems without these undesirable effects. "A laser is a device that creates a very narrow, highly directional beam of light," explains Svetlana Malinovskaya, professor at the Charles V.
School of Engineering and Science, whose research focuses on quantum science and controlling quantum systems. "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 this powerful wave reaches a quantum system, its units of energy, called photons, are absorbed by the atoms and molecules of that system, pushing these particles into a higher-energy state. If the laser field is very intense, an atom or molecule may interact with multiple photons at once, opening additional pathways between its energy states and disrupting the desired dynamics in the quantum system, making it difficult to predict or control.
These unwanted interactions are called multiphoton processes. "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." That unpredictability is a major problem when scientists need precise control—for example, when manipulating quantum systems for quantum computing or making highly sensitive measurements.
"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." In these applications, light-matter interactions must be controlled with extreme precision, so researchers want to use just enough light to control a quantum system without introducing unwanted processes. In their new study, Malinovskaya and her collaborators propose solving this problem with what they call a "digitized" version of a laser pulse.
Their calculations show that using a series of 12 short, low-intensity laser pulses would produce the same effect as one long, intense pulse, but without pushing the atoms or molecules into unwanted states that are difficult to control. "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." Discover the latest in science, tech, and space with over 100,000 subscribers who rely on Phys.org for daily insights. d research that matter—daily or weekly.
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