Non-destructive control of single atoms

An optical lattice is a periodic optical potential field (it has spatially dependent potential energy) created by the interference of counter-propagating laser beams. The dynamics of ultracold atoms in optical lattices are very much like those of solid-state systems, but with superior purity, regularity and tunability. This makes optical lattices a fertile test bed for the most exciting predictions in quantum engineering.

With EU support of the project 'Quantum control: Manipulating and interfacing selected atoms in optical lattices with light' (QNDLATTICE), scientists set out to merge the study of ultracold atoms in optical lattices with non-destructive (quantum non-demolition (QND)) measurements. QND measurements exploit the interaction of light with the atomic states in optical lattices. They enable one to observe a quantum system without altering it due to interference with the measurement apparatus itself.

Optical imaging of a single lattice site was achieved just prior to initiation of the reintegration grant, but the optical approach is expensive and technically quite complicated. During the reintegration phase, researchers focused on QND detection and manipulation in the optical lattice. In addition to being simpler, this technique is more sensitive because it exploits frequency that is relatively easy to control.

Given the lack of theoretical background merging the two distinct fields, the QNDLATTICE group developed the required simulation code. This enabled scientists to create and publish new architectures for scalable quantum computation, atomtronics and quantum control of many-body states using QND measurements. Development of a new laser system for QND imaging of ultracold atoms led to the first-ever probing of such atoms in optical lattices using the Faraday interaction (of light and a magnetic field).

The experimental setup and theoretical background for QND manipulation of individual sites in an optical lattice have been established. The objective is expected to be reached within a half-year of project-end. Access to an inexpensive and relatively simple experimental setup to manipulate the spin of a single atom will open a new window onto the quantum world. It will be an invaluable tool in the hands of the best and brightest.