Abstract
A significant challenge in atomic physics is the precise preparation, manipulation, and measurement of the quantum-mechanical states of physical systems. One intriguing aspect of multi-particle quantum states is entanglement. Entanglement is of high interest for conducting non-classical computations, particularly in the application of quantum information, and the enhancement of measurements through entanglement. Spin-entangled states in many-body systems have been engineered and verified via spin-changing collisions. Using optical tweezers to isolate individual atomic pairs provides a unique avenue for investigating spin-changing collisions and the entangled states at the particle level. Up until now, the entanglement for an atomic pair has been achieved with groundstate-cooled atoms. The ability to generate entanglement at a higher temperature would be a step forward to robust practical applications in real world scenarios.
In this work, we use hot spin-changing collisions as a pathway to generate entanglement. In previous studies conducted in our laboratory, we examined the population dynamics of the magnetic sub-levels within a pair of 85Rb atoms confined in an optical tweezer. These atoms, initially in a F=2, mF=0 state, undergo spin-changing collisions, resulting in strong correlations between the states F=2, mF=1 and mF=−1. To investigate the entanglement between the atoms, we utilize a Raman transition pulse that couples the two magnetic sub-levels, resulting in destructive interference when the atoms are entangled. Our experimental measurements, combined with a numerical simulation that accounts for the full atomic level structure in the presence of the Raman pulse, demonstrate that the spin-changing collisions effectively generate entanglement between the two atoms. Furthermore, our findings reveal that this resulting entanglement can be used to enhance the magnetic field measurements, surpassing the conventional quantum limit.