Simulation is crucial to many sciences. We simulate cosmic events before we spy them in the skies. We simulate molecular dynamics to inform our synthesis of new drugs. We simulate electronic circuits before we build them, and quantum circuits are no exception.
But simulating a quantum circuit is especially difficult. Quantum systems evolve in a complicated way, and keeping track precisely enough requires lots of computer memory and time. Every additional qubit in a simulated quantum computer doubles the memory requirement and the runtime; if simulating a single qubit computer took only 1 second, simulating a 60 qubit computer would take longer than the age of the universe and require 17 billion times the RAM in your 8GB laptop!
Real quantum computers are already becoming too large to simulate! To keep up, it’s vital our simulators utilise all the tricks used to make classical computers run as fast as possible. To this end, we’ve released QuEST, the Quantum Exact Simulation Toolkit, a C-based simulator of quantum computers. QuEST combines several high performance classical computing techniques to simulate quantum computers at lightning speed. QuEST can run on multiple CPUs, on a GPU, and on multiple linked computers (the first open source quantum computer simulator to do so!), and can be used to simulate quantum circuits too large to fit on a single computer.
You can read more about QuEST here, read our paper comparing QuEST to other state-of-the-art simulators here, or download QuEST from github.
