Universality of quantum diffractive collisions and the quantum pressure standard

Abstract

This work demonstrates that quantum diffractive collisions are governed by a universal law characterized by a single parameter that can be determined experimentally. Specifically, we report a quantitative form of the universal, cumulative energy distribution transferred to initially stationary sensor particles by quantum diffractive collisions. The characteristic energy scale corresponds to the localization length associated with the collision-induced quantum measurement, and the shape of the universal function is determined only by the analytic form of the interaction potential at long range. Using cold ^87 Rb sensor atoms confined in a magnetic trap, we observe experimentally ${p}_{\mathrm{QDU}6}$ , the universal function specific to van der Waals collisions, and use it to realize a self-defining particle pressure sensor that can be used for any ambient gas. This provides the first primary and quantum definition of the Pascal, applicable to any species and therefore represents a fundamental advance for vacuum and pressure metrology. The quantum pressure standard realized here is compared with a state-of-the-art orifice flow standard transferred by an ionization gauge calibrated for N _2 . The pressure measurements agree at the 0.5% level.

Keywords

• atom and molecular physics
• cold atoms
• metrology
• units and standards
• pressure
• vacuum based detection