Quantum computers could one day solve some of the world’s toughest problems, and they’d do this by working completely differently to a regular computer. Information is stored in your laptop in bits. Every bit is either a one or a zero: up or down. But quantum computers are made of qubits. Unlike bits, qubits can be a mixture of one and zero at the same time. Quantum computers are made of several entangled qubits with all their states connected together. But actually building a quantum computer is a challenge. In normal computers it’s easy to add more bits, but for quantum computers the more qubits you have the harder it is to add one more. This makes it tricky to scale up from a simple quantum computer to something more powerful. Another problem is that quantum computers have to keep their qubits protected. Too much interference from the outside world and the entanglement is broken. But overcoming these challenges and building a powerful quantum computer would come with big rewards. Take searching: imagine you have a bunch of mixed-up business cards. How would a computer find the right one? A normal computer has to look through, one by one, until it eventually finds the right card. But a quantum computer has a trick up its sleeve. Because the quantum computer is in many states at once, it can search all the cards at once. After several sweeps it finds the card. And quantum computers could help tackle all sorts of other problems, like modelling protein folding, and cracking data encryption. But, even if scientists can one day build a powerful quantum computer it probably wouldn’t be useful for everyday tasks, so don’t throw away your laptop just yet.