How can we work with quantum computers today?

Quantum computers are a new, promising technology still in its infancy. Our conventional computers are already quite powerful. But this new technology could speed things up a lot! Because of this, many computer companies have already started building quantum computers. Unfortunately, they are still rather small compared to what we expect in the future. So how can we prepare programmers and users for this new technology? One way to do so: simulate the quantum computer on our conventional machines. Of course, this is very complex – if it were easy, we would not need a quantum computer in the first place. Here we propose a method that tackles this complexity using so-called decision diagrams. We tested our method by attempting several different quantum computations. Then we compared it to the other existing simulators. Our approach outperforms the other solutions in many cases. This allows everyone to simulate quantum computations today – even before the really powerful quantum computers are available.