Quantum mechanics is an extraordinarily profitable way of understanding the physical world at extraordinarily small scales. Via it, a handful of rules can be utilized to explain the vast majority of experimentally observable phenomena. Sometimes, however, we come throughout a problem in classical mechanics that poses explicit difficulties for translation into the quantum world.
New research revealed in The European Physical Journal D has provided some insights into one among them: momentum. The authors, theoretical physicists Di Pumpo and Matthias Freyberger from Ulm University, Germany, current an elegant mathematical model of quantum momentum that’s accessible by means of another classical concept: time-of-flight.
Many individuals will recall the standard definition of momentum from high-school physics as denoting the product of the mass of an object and the rate at which it’s traveling. In quantum theory, an object is described by a wave function, and its position can’t be determined except the wave function is ‘collapsed’ into a single state. This is the nature of measurement in quantum mechanics.
Classical momentum will be obtained just by measuring the time an object takes to pass between two stationary detectors (‘time-of-flight’), discovering the velocity and multiplying by the mass. Fabio Di Pumpo and Freyberger have developed a model of the quantum equivalent of this experiment through which the roles of time and distance are reversed: the time points are fixed, and the probabilistic positions of a wave function at each end, and thus the gap between them, estimated. This method uses new quantum systems known as pointers that are coupled to a transferring wave packet utilizing a technique developed by von Neumann, with measurements made to the pointers rather than the wave.