German physicists from Kaiserslautern and Hanover have successfully used a single cesium atom as a sensor for ultracold temperatures. By utilizing quantum states, they collected certain parameters relating to air pressure and temperature.
The team measured data from the angular movements or spin of the atom. The highly sensitive system uses the spinning to measure the temperature of an ultracold gas and the magnetic field. This discovery, recently published in “Physical Review X“, can be useful for future investigations into quantum systems without interference.
Dr. Artur Widera researches quantum systems at Technische Universität Kaiserslautern (TUK). He and his team observed individual cesium atoms in a rubidium gas that reached near absolute zero degrees. Amazingly, they can measure the temperature down to “one billionth of a fraction of a degree above this zero point.”
They investigated whether the cesium atom’s spin states can be used to gather information. Dr. Widera explains; “The term spin refers to the intrinsic angular momentum of an atom. In cesium, there are seven different orientations for this spin.”
When a single cesium atom is added to the rubidium gas, it causes a collision. Lead scientist and first author Dr. Quentin Bouton explains; “This [collision] allows angular momentum to be exchanged between the atoms until a balance of spin is achieved.” And, once that balance is achieved, they can determine the temperature from the spin measurement. Bouton continues his explanation:
In fact, for quantum sensors, there is a fundamental limit to their sensitivity in equilibrium. However, we included information about the interactions between cesium and rubidium in advance, so we did not have to wait until the atom was in equilibrium with the rubidium gas. We only needed three spin-exchange processes, in other words, three atomic collisions, to arrive at a result.
The Kaiserslautern researchers’ new measuring system is nearly ten times more sensitive than the fundamental quantum limit requires. This in turn also limits the perturbation of rubidium gas to only three quanta. It is important to have as little an amount of perturbation as possible when measuring sensitive quantum systems.
Dr. Widera points out; “This is the first time we have used a single atom as a sensor that uses quantum information and is significantly better than a classic sensor.” The team also tested this method with magnetic fields to determine how it affected magnetic states.
They are hopeful this can help with further research in highly sensitive quantum systems, and generate positive results with little or no destruction.
