Simulating 2D Spin Lattices with Ion Crystals


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The objective of this project is to experimentally realize a 100-particle quantum simulator with complete quantum control at the single-particle level . We combine the proven methodology for realizing spin models in linear ion crystals stored in radio-frequency traps with a novel approach to extending such a system into two dimensions, thus enabling studies of 2D non-equilibrium physics with a larger particle number.


Analog quantum simulation with trapped ions in Innsbruck


In Innsbruck an analog quantum simulator based on 1D strings of Calcium-40 ions stored in a linear Paul trap is already used successfully to study systems of interacting spins with up to ~20 particles. In the approach used here and several other groups around the world, a spin-half particle is encoded into two electronic states of a trapped ion, which is manipulated via laser pulses: coherent single-ion operations and measurements are combined with engineered spin-spin interactions mediated by the motional modes of the ion crystal to directly implement e.g. Ising-type Hamiltonians in the system.


Why extend the system into the second dimension?




Scaling up an ion chain to a large number of particles (>50) presents a challenging task as extremely anisotropic trapping potentials are required to keep the ion crystal linear, leading to issues such as high heating rates of the axial motional modes as well as problems in addressing outer ions in long strings. In our approach of using 2D ion crystals, such problems can be circumvented, which will enable us to scale our quantum simulator up to 100 particles.


Our approach


Two experimental setups are currently in the process of being built from scratch:

  • A room-temperature setup, to initially test key experimental techniques on small 2D ion crystals
  • A cryogenic setup: The cryogenic environment will reduce collisions of the ions with background gas and decrease motional heating of the ions due to fluctuating stray electric fields. In this setup we will be working with large 2D ion crystals of up to 100 particles.

In both setups we aim to trap planar ion crystals in a novel micro-fabricated segmented linear Paul trap. Here, we investigate a 3-layer trap design, based on ideas by the ETH ion trapping group, as well as a monolithic design, shown below. The geometry of these traps allows us to create the anisotropic potentials required for trapping 2D ion crystals while still being able to maintain sufficient optical access for imaging and addressing. In our approach, each spin-1/2 particle is encoded into the 4S 1/2 ground state Zeeman manifold of the single outer valence electron of a Calcium-40 ion. The spin states are coupled via a Raman transition using a global light field at 395 nm. Additionally, an addressing unit based on a 2D acousto-optic deflector will enable us to coherently manipulate individual spins.


monolithictrap Comsol


Our main experimental goals


  • Trapping and laser-cooling of two-dimensional ion crystals to millikelvin temperatures in a radio-frequency trap.
  • Realization of quantum spin models with particle numbers for which the simulation becomes intractable by numerical techniques.
  • Development of methods for validating quantum simulators.
  • Investigation of various models with spin-frustration in two-dimensional geometries.


Project members



Image credit: M.R. Knabl/IQOQI


  • Christian Roos (Project Leader)
  • Helene Hainzer (PhD Student)
  • Dominik Kiesenhofer (PhD Student)


We currently have positions available for Postdocs. For more information, please This email address is being protected from spambots. You need JavaScript enabled to view it.




Funding for this project is provided by the European Research Council (ERC) via an ERC
Advanced Grant (Project SPICY).

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