Eth Zürich Team Detects Atom Impacts with 96% Certainty

Maxime Perdriat and colleagues at École Normale Supérieure PSL, Sorbonne University, CNRS and Laboratoire Kastler Brossel have observed single momentum kicks resulting from xenon atoms colliding with a levitated nanosphere cooled to its quantum ground state, measured with 96% confidence. This sensitive detection of atomic impacts enables investigations into fundamental interactions at tiny scales. The team has achieved an unprecedented ability to measure forces from individual xenon atoms impacting minuscule, suspended particles. By observing tiny displacements, smaller than those caused by typical gas molecules, they enable these investigations.

This method also establishes a foundation for creating new sensors capable of detecting incredibly weak impulses, opening possibilities beyond current limitations in force measurement technology. They accomplished this feat through careful control of atomic beams; creating a focused stream of atoms resembles releasing compressed air from a tyre, resulting in a slow but directed flow.

Measuring minuscule displacements of the nanosphere caused by these collisions, smaller than those induced by typical gas molecules, allowed detection of momentum transfers as small as 50 keV/c, akin to comparing the gentle push of a breeze with that of a strong gale. The technique not only allows investigation into fundamental interactions at tiny scales but also paves the way for novel sensors; however, discerning genuine atom impacts from background noise requires sophisticated analysis detailed below.

Detection of individual atom collisions via optically levitated nanoparticle momentum exchange

Momentum kicks as small as 50 keV/c were observed, representing an improvement exceeding three orders of magnitude over previous limits imposed by α particle recoil. This advancement allows resolution of individual atom collisions that had previously been undetectable due to limitations in measurement sensitivity. Until now, only larger displacements caused by thermal motion or groups of atoms could be registered. The technique utilises a levitated nanosphere cooled to its quantum ground state, where all movement ceases, minimising background noise and enabling detection of these subtle momentum transfers from focused beams of xenon atoms.

Directional momentum transfer originating from the xenon atomic beam was confirmed against background thermal collisions. Individual momentum kicks occurred with ninety-six percent confidence, while maximum measured transfers reached approximately fifty keV/c, roughly twenty-five times the zero-point fluctuations within the system. Statistical analysis proved an ability to detect events specifically stemming from focused xenon interactions instead of general chamber thermal motion; control experiments blocking the supersonic beam reduced collisions to just 3.6 counts per second when nitrogen purged the chamber.

Detecting individual xenon atom interactions unlocks potential nanoscale force measurement

A levitated nanosphere now offers exciting possibilities for nanoscale sensing through detection of single xenon atoms. The current setup relies on carefully controlled beams delivered via supersonic expansion, demanding substantial infrastructure not readily available in all laboratories however. While effective at isolating atomic impacts from background noise, this method presents practical hurdles compared with alternative approaches utilising simpler vacuum systems or different particle sources. This breakthrough enables measurements of incredibly small forces, below 50 keV/c, and differentiates genuine atomic impacts from random thermal motion with ninety-six percent confidence. Optical levitation techniques suspend objects in mid-air using light pressure and were key to cooling the nanoparticle to its quantum ground state; employing focused beams created through supersonic expansion isolated directional momentum transfer and opened new possibilities for investigating interactions between atoms and suspended systems.

The research demonstrated detection of individual collisions between xenon atoms and a nanosphere cooled to its quantum ground state. This is important because it allows scientists to measure extremely weak forces, below 50 keV/c, and distinguish these specific events from background noise with 96% certainty. By utilising a combination of optical levitation and carefully controlled atomic beams, researchers observed directional momentum transfers resulting from these impacts. The authors suggest this work represents an initial step towards exploring short-range interactions at the nanoscale and developing sensitive force sensors.