Asked by: Brian Shimell, Surrey
Conventional computers use electrical signals that represent binary 1s and 0s, or bits. Their building blocks are logic gates such as ‘AND’, ‘OR’ and ‘NOT’ which determine whether an output is a 1 or a 0. Quantum computers operate using qubits, which hold all possible states simultaneously, and only when their final state is measured will their final state become a reality. Quantum gates are made by using quantum entanglement, so looking at the state of one tiny particle will tell you about the state of the other. There are many varieties of quantum gate, both in theory and in practice, some resembling conventional logic, some a little bizarre, like ‘square root of NOT’.