Explain It Like I'm Five: Quantum computers

What are quantum computers?

Computers that use principles of quantum physics to run computations, which could make them really fast: One designed by Google completed 47 years' worth of tasks in a few seconds.

How do they do this?

Typical computers use bits, units of data that can either exist as a 0 or a 1. Quantum computers use quantum bits, or “qubits,” which can be a 0 and a 1 simultaneously. In quantum physics, this is called superposition.

How can it be two things at the same time?

Okay, technically, that’s an oversimplification. Like Schrödinger’s cat, qubits have a mathematical probability of being either one (as well as several states in between) until the computer reads it. When you get a bunch of qubits together, all in superposition, all of those probabilities give a computer millions of different paths to completing a calculation, which are executed simultaneously.

If a computer is running a bunch of possibilities at once, isn’t it going to give you a bunch of correct and incorrect results?

That’s one thing holding quantum computers back right now. A reason companies want more qubits in computers is to have a redundancy with the qubits that are actually running a program, effectively checking their work. Right now, the best quantum computers have an error every 1,000 operations. That needs to get down to one in a million to be more feasible.

How will I use quantum computers?

You won’t have one in your home or phone — they’re probably going to be used for the kinds of tasks supercomputers are used for today. But that could still have a big impact across sectors as running millions of simultaneous simulations of chemical reactions could yield breakthroughs in things ranging from medicine to fertilizer to car batteries. It could also make more capable AI, or develop more advanced ways to encrypt data.