Focus on... Cold Atoms

Cold Atoms

Cold neutral atoms offer an exciting alternative approach to quantum computing and simulation, being based on individual atoms trapped and manipulated with laser light and microwaves.

There are two main platform classes built using neutral atoms: Analogue quantum simulators with neutral atoms moving in potentials made of laser light; and tweezer arrays, where atoms are individually trapped and manipulated either as individual qubits with digital quantum gate operations, or in an analogue fashion with the qubits acting as individual spins. The primary upside of both these platforms over other means of implementing quantum computing and simulation is in the ease with which we can control large numbers of identical qubits.

Leading systems internationally currently reach well over 1000 particles when used for analogue quantum simulation, and over 250 when trapped individually in tweezer arrays. The biggest challenges for these platforms are in realising either high-fidelity and fast gate operations for digital quantum computing, or in realising highly- calibrated, programmable local control for analogue quantum simulation. For example, by loading cold atoms in standing waves of laser light, we can realise an optical lattice, or a crystal potential in which the atoms move. In such systems, we generally have separate control of the potential landscape for the atoms and the interactions between atoms. These setups can be used to build models of electrons moving in solid-state crystals, from which we can learn or test the building blocks of our understanding of modern solid-state materials, involving strongly interacting electrons. The effective computational problem of determining the dynamics of interacting microscopic particles in such a setting are widely understood to be exponentially complex to simulate on classical computers, and by implementing them in the laboratory we can observe their properties and effectively solve the corresponding models. The challenges are threefold: To develop the level of local control and readout necessary to manipulate and measure these systems on the level of single atoms and single lattice sites; to increase the precision of the calibration of all model parameters so that the solutions are reliable; and to understand how to make use of these to extract useful information beyond what can be accessed through calculations on classical supercomputers.

In the QCS hub, we combine experimental and theoretical teams to address these key challenges. We have experimental teams from the University of Strathclyde (led by Stefan Kuhr) and the University of Cambridge (Ulrich Schneider), who are developing and testing individual control of cold atoms in optical lattices, manipulating the initial states for atoms and the potential landscape in which they move by using spatial light modulators and optical tweezers, which impose a potential on top of an existing optical lattice. In addition, we have two theory teams, led by Andrew Daley (University of Strathclyde) and Dieter Jaksch (University of Oxford). They are exploring the calibration and control requirements for attaining a practical quantum advantage with these systems over known classical calculation methods, and exploring potential use-cases of these systems as quantum co-processors to classical supercomputing calculations – especially with applications in materials science.

You can find ourt more about our Cold Atoms work, as well as the rest of the Hub's research in our 2022 Progress Report, downloadable here.