Before the advent of digital computers, sophisticated orreries were used to predict the positions and motions of astronomical bodies. Today, we are witnessing the renaissance of devices that simulate, rather than calculate, the evolution of complex many-body systems. Quantum simulators — which use one controllable quantum system to investigate the behaviour and properties of another, less accessible one — hold the promise of tackling problems that are too demanding for classical computers. Over the past few years, significant progress has been made in a number of experimental fields, as reviewed in this Insight, which also considers where quantum simulation might take us.
The long-term promises of quantum simulators are far-reaching. The field, however, also needs clearly defined short-term goals.
Quantum simulations with ultracold quantum gases
Experiments with ultracold quantum gases provide a platform for creating many-body systems that can be well controlled and whose parameters can be tuned over a wide range. These properties put these systems in an ideal position for simulating problems that are out of reach for classical computers. This review surveys key advances in this field and discusses the possibilities offered by this approach to quantum simulation.
Quantum simulations with trapped ions
Experimental progress in controlling and manipulating trapped atomic ions has opened the door for a series of proof-of-principle quantum simulations. This article reviews these experiments, together with the methods and tools that have enabled them, and provides an outlook on future directions in the field.
Photonic quantum simulators
Quantum optics has played an important role in the exploration of foundational issues in quantum mechanics, and in using quantum effects for information processing and communications purposes. Photonic quantum systems now also provide a valuable test bed for quantum simulations. This article surveys the first generation of such experiments, and discusses the prospects for tackling outstanding problems in physics, chemistry and biology.
On-chip quantum simulation with superconducting circuits
Lithographically fabricated micrometre-scale superconducting circuits exhibit behaviour analogues to natural quantum entities, such as atom, ions and photons. Large-scale arrays of such circuits hold the promise of providing a unique route to quantum simulation. Recent progress in technology and methodology are reviewed here, and prospects and challenges discussed.
In the field of quantum information processing, it is one of the grand challenges and visions to build in the laboratory a quantum device which performs tasks not achievable on a classical level. A next generation quantum simulation experiment involving (experimentally proven) large-scale entanglement may be the first laboratory demonstration that fulfills this promise in a convincing way. This would be an exciting and big step forward towards the realization of Feynman’s 30-years-old dream of building a programmable quantum simulator, which might not only provide us with answers to long-standing open questions, but also allow us to explore new realms of physics, such as many-body quantum dynamics beyond thermodynamic equilibrium