Atomtronics: Fundamental Limits on quantum transport

Atomtronics is the science of manipulating atoms in complex potentials much like electrons in electronic circuits. Mattewaves consisting of atoms are promising candidates for the realization of extremely sensitive sensors. They could also form the basis for complex atom-circuit quantum computers. Indeed, some of the most sensitive and precise measurements to date of gravity, inertia, and rotation are carried out using matter-wave interferometry albeit with free-falling atomic clouds. Another important potential application is circuit quantum computation. A critical requirement to achieve very high sensitivities is the long interrogation time, which consequently leads to experimental apparatus up to a hundred meters tall or the requirement for experiments to be performed in microgravity in space. To tackle this problem, the gravitational acceleration must be cancelled, e.g. by manipulating atomic waves in time-changeable traps and waveguides. In the past, we demonstrated near-perfect smooth and controllable matter-wave guides by transporting Bose-Einstein condensates (BECs) over macroscopic distances without any heating or decohering their internal quantum states. A neutral-atom accelerator ring was utilized to bring BECs to very high speeds (up to 40 times their sound velocity) and transport them in a magnetic matter-wave guide for 15 centimetres whilst fully preserving their internal coherence.

If this represents a ‘perfect’ waveguide then what is a non-perfect waveguide? How much imperfection can a waveguide tolerate before it starts to harm quantum-transport? In this presentation, we will introduce the basics of TAAP waveguides and explore experimentally how strong an obstacle has to be in order to disturb the travelling matterwave. We propose a simple fundamental quantum limit which depends only on the transverse confinement of the atoms.