CORDIS - Forschungsergebnisse der EU

A Quantum Non-Demolition Microscope

Final Report Summary - QUANTUMPROBE (A Quantum Non-Demolition Microscope)

Quantum phenomena have an increasing impact onto applications. Quantum gases have proven versatile tools to study quantum phenomena in an exceptionally clean and controllable environment. At the same time, a high level of control has been developed to control and manipulate quantum properties of individual quantum objets, such as single neutral atoms.
The project QuantumProbe has brought together those previously distinct areas. It immerses single highly controlled, ultracold Caesium atoms into an ultracold gas of Rubidium atoms in order to detect and steer intricate quantum properties of complicated many-body states. This system envisions the use of single atoms as microscopic, non-destructive probes to detect and map out properties of a fragile quantum many-body system.
Technologically, this vision requires simultaneous preparation of both, a quantum gas and tightly controlled single ultracold atoms, which are subsequently brought into contact.
To this end, an experimental apparatus was designed and constructed, which features rapid production of a Bose-Einstein condensate of Rubidium atoms as quantum many-body system on the one hand; and cooling and trapping of individual neutral ultracold Caesium atoms on the other hand. Bringing together ultracold gas and individual atoms transfers the exceptional control over individual atoms onto a quantum many-body system. In all these three areas of quantum gases, single atoms and the combination of both, the project could advance current state-of-the-art.
First, control and investigation of individual neutral atoms and their properties in engineered potentials allowed to observe fundamental properties of single atoms diffusing in periodic potentials. This system is an ideal model system for various phenomena, including diffusion on surfaces or in structured environments, superionic conductors, or Josephson junctions. The results obtained are thus not specific to the cold atom system but allow drawing rather general conclusions to similar diffusion systems in biology, medicine or soft matter systems.
Second, technological optimization of production of quantum gases as well as novel tools for quantum gas manipulation allowed for precision measurements of atomic properties, yielding a deepened insight into the atomic structure of atomic species used.
Third, the experimental apparatus has enabled us tracking the dynamics of a single atom interacting within a gas with high spatial and temporal resolution. This is reminiscent of single particle tracking in fluorescence imaging, but here brought to the extreme limit of tracking the motion of a single tagged atom within an ultracold gas. The information obtained from the measurements of these probe atoms has allowed to establish a temperature measurement of the ultracold gas using the individual atoms as non-destructive, local thermometers. Furthermore, we have realized and studied the so-far unexplored regime of particle diffusion dominated by individual atomic collisions. Beyond their relevance to related phenomena in atmospheric physics, for example, our results directly point toward further investigations of quantum properties or toward simulation of impurity physics on a single atom level.
While the immediate results have relevance and impact far beyond the physics horizont of the project, the technological advance and scientific results have opened the door to establish single atoms as microscopic probes for a quantum many-body system.