The idea of a quantum simulator was proposed by Yuri Manin in 1980 and Richard Feynman in 1982 who famously wrote: “Nature isn’t classical, dammit, and if you want to make a simulation of nature, you’d better make it quantum mechanical”. The core concept is the use of a controllable quantum system to mimic and study complex quantum systems that are intractable on classical computers. Quantum simulators are purpose-built to solve specific problems in quantum physics, chemistry and material science and should be differentiated from “digital” quantum computers which can solve a wider class of problems—although digital quantum computers can of course be used to tackle simulation problems.
How do quantum simulators work?
The basic ingredients for quantum simulation are:
- Target system mapping: identify the quantum system to be studied and map its Hamiltonian energy structure onto the simulator’s physical platform;
- Parameter control: precisely control the simulator’s parameters, such as interaction strength to match those of the target system;
- Preparation: initialize the simulator in a desired quantum state that corresponds to the initial conditions of the target system;
- Time evolution: let the simulator evolve naturally under its Hamiltonian, mimicking the dynamics of the target system;
- Readout: measure observable of interest to extract the relevant quantity about the target system.
Frequently asked questions.
- What is the difference between a quantum simulator and a quantum computer? Quantum simulators are specialized devices optimized for specific simulation tasks, while universal quantum computers can theoretically perform any quantum computation (and in particular quantum simulations). However, it is of course more difficult to build a general-purpose quantum computer.
- What fields are directly impacted by quantum simulations? Examples are \(i\) condensed matter physics (phase transitions, magnetic ordering, exotic phase of matter like quantum spin liquids, …), \(ii\) quantum chemistry (molecular dynamics, chemical reactions, electronic structure of complex molecules, …), \(iii\) high-energy physics (quantum field theories), \(iv\) material science (designing new materials).