Lecture“ Matter-wave interferometry with ultracold atoms”

We cordially invite you to the lecture, which will take place in the hall of the ISI CAS on 2 April 2025 at 10:00. The topic will be presented by Prof. Christopher Foot, University of Oxford.

Abstract
Two applications of atom interferometry that we are currently working on in Oxford will be described. Firstly, an experiment in which rubidium atoms are cooled to temperatures of tens of nanokelvin, resulting in a phase of matter where the lowest energy quantum state is macroscopically occupied, called a Bose-Einstein condensate. Such matter displays quantum mechanical properties on a macroscopic scale. For example, when released two clouds of atoms in this state expand as they freely fall and the wave-nature of matter leads to the formation of interference fringes in the overlap region, analogous to those in a Young's double-slit experiment with light. From the phase of the interference fringes we read out information about the macroscopic wave function of the quantum gases. This is a powerful method for investigating non-equilibrium physics in many-body quantum mechanical systems, i.e. by observing the time evolution of the quantum system after a quench (a sudden change of conditions) [1].  Secondly, our work towards the development of a large-scale interferometer using strontium atoms will be outlined. This is an analogue of a Mach-Zehnder interferometer in which the roles of light and matter are reversed as compared to an optical device: the atomic wave packets are split, deflected and recombined by pulses of laser light. This exploits the special properties of an extremely narrow transition in strontium, which is also used for the best optical-lattice clocks, and allows this type of interferometer to be made large. A prototype that is 10-metre tall is planned by the AION collaboration (of 7 institutions within the UK) and even taller instruments are under construction elsewhere for tests of fundamental physics. A very long-term goal of this method of atom interferometry is the detection of gravitational waves (requiring scaling up by several orders of magnitude) in a frequency band around 1 Hz not measurable with current terrestrial experiments.

[1] Universal scaling of the dynamic BKT transition in quenched 2D Bose gases.  Sunami et al. (2023) Science 382, 443. DOI:(10.1126/science.abq6753)