Rubidium atoms can behave unpredictably during atomic collisions, especially when exposed to specific laser light. Researchers have now discovered that these tiny interactions can release unexpected bursts of energy, sometimes powerful enough to expel atoms from carefully controlled traps.
The findings, led by scientists from the University of Colorado Boulder and the University of Massachusetts, could improve our ability to manipulate atoms for quantum computing and molecular physics.
Understanding Cold Atomic Collisions
Ultracold atomic gases allow scientists to observe quantum behaviors that are otherwise difficult to detect. At temperatures near absolute zero, atoms move so slowly that quantum effects dominate their interactions.
A research team led by Professor Cindy Regal and Jose D’Incao investigated light-assisted atomic collisions, in which laser photons nudge atoms into temporary superposition states. This phenomenon means that either atom in a collision could have absorbed a photon, leading to sudden bursts of energy.
In some cases, these bursts were strong enough to eject atoms from their optical traps, disrupting the experiment.
The Role Of Hyperfine Structure
One of the study’s key insights is the influence of hyperfine structure on atomic collisions. Hyperfine structure results from the interaction between an atom’s nuclear spin and the angular momentum of its electrons.
Although these energy shifts are usually small, the research team found that they significantly impact collision rates.“This energy is imparted to the colliding atoms, which can be considered bad as they are large enough to cause atoms to escape from typical traps”, said Professor Regal. “But these collisions can also be useful when that energy can be controlled.”
Optical Tweezers For Precision
To conduct their experiments, the researchers used optical tweezers—highly focused laser beams that can trap individual atoms. By placing two rubidium atoms in separate tweezers and merging them under controlled conditions, the team measured how different laser frequencies affected collision outcomes.
By carefully adjusting laser frequency, they could control the energy transfer during each collision. This level of precision was difficult to achieve in previous studies that used larger atomic clouds rather than individual atoms.
Detecting Atomic Collisions Without Interference
Traditional imaging systems can make it challenging to measure atomic collisions accurately. Shining light to check whether atoms remain trapped can sometimes alter their energy state, affecting the results.
To solve this issue, Steven Pampel, the study’s first author, developed a new method to detect ejected atoms without disturbing the system. This technique allowed the team to gather more accurate data and refine their models for how rubidium atoms interact under laser light.
Potential Applications In Quantum Computing
These findings could have significant implications for quantum computing and molecular physics. In quantum computing, trapped atoms are often used as qubits, the building blocks of quantum information processing. Improved control over atomic collisions could lead to more reliable quantum devices.
Beyond computing, this research could help scientists better understand molecular interactions. By extending these methods to different atomic species, researchers might uncover new ways to manipulate quantum states for future experiments.
