QUROPE Quantum Information Processing and Communication in Europe

Objectives: Quantum simulation uses controllable quantum systems to investigate the properties of other complex quantum systems, and can tackle problems that are beyond the computational capability of any classical computer. Initial experimental and theoretical work has been mainly directed towards the quantum simulation of condensed matter systems, such as bosonic or fermionic particles in lattices, but more recent work also encompasses such diverse fields as quantum field theory, cosmology and high-energy physics.

State of the art: Experimental platforms for quantum simulation comprise ultracold atomic and molecular quantum gases, ion traps, polariton condensates, circuit-based cavity quantum electrodynamics and arrays of quantum dots or Josephson junctions. All of these platforms aim to explore the potential of quantum simulations for different fields of science. The first demonstrations of quantum simulation were performed on ultra-cold atoms. In this platform, the quantum-gas microscope technique has opened up novel possibilities to probe and manipulate cold-atom quantum simulators at the single-particle level. For trapped ions, the extraordinary level of control of motional and internal quantum states has enabled for example the realization of a digital quantum simulator, and analogue quantum simulation of different spin systems. Recently, also solid-state systems like coupled arrays of cavities or superconducting qubit arrays, or arrays of defect centres, are being explored for quantum simulation purposes.

Future directions: The challenges of the science of quantum simulation can be divided into four categories that need to be addressed:

• Novel manipulation and detection schemes for quantum many-body systems to further improve the controllability of artificial quantum matter realized for quantum simulation purposes. This includes improving fidelities of present preparation schemes, as well a devising novel measurement and control techniques and also include identifying completely novel systems for quantum simulations.
• Extend the reach of quantum simulations into other fields of science, e.g. quantum field theories in high-energy physics, nuclear physics, cosmology (simulation of non-equilibrium dynamics), biology, chemistry and material science.
• Novel strategies toward lower temperatures and entropies of many-body systems. This will allow exploring novel quantum phases of matter that could find important impact in metrology (e.g. atomic clocks), quantum computing or material science.
• Novel strategies for the verification of quantum simulations, studying how finite temperature errors and imperfections in implementations of couplings affect the resulting many-body state.