In 1982 Richard Feynman conceived of a “quantum mechanical computer.”1 His central idea was that a quantum device could take advantage of quantum entanglement and superposition to make calculations that are impossible on a classical computer. Two descendants have emerged from that conception: quantum simulation and quantum computing.
In a quantum simulator, one quantum system is used to model the behavior of a different quantum system. For the past 15 years, quantum simulators have taken advantage of the simplicity and controllability of ultracold atoms and ions to study a wide range of many-body physics, including aspects of Hubbard models, quantum magnetism, superconductivity, and the solutions to many other quantum models, both previously conceived and newly invented. A quantum computer is conceptually akin to a digital classical computer, with classical bits replaced by quantum bits, called qubits, that can exist in superpositions of states and can be mutually entangled. The...