Quantum computer circuitry illustration. Conventional computers store information as 'bits', with each transistor holding either a 1 or a 0. Quantum computers use quantum bits, or qubits, which operate according to two principles of quantum physics. One of the principles, supposition, allows a qubit to store a 1 and a 0 at the same time. This means two qubits can hold four values at once. The second principle, entanglement, means that the state of one qubit can depend on the state of another. As you expand the number of qubits, the machine becomes exponentially more powerful.