Methods, systems, and apparatus for quantum random number generation. In one aspect, a method includes initializing N qubits in respective superposition states; computing a randomly selected oracle randomization function using i) the initialized N qubits and ii) multiple ancilla qubits, wherein the multiple ancilla qubits comprise a first ancilla qubit and one or more second ancilla qubits; performing a phase flip operation on the first ancilla qubit; computing an inverse of the randomly selected oracle randomization function using i) the N qubits and ii) the multiple ancilla qubits; performing a diffusion operation on the N qubits; and measuring the N qubits and providing data representing the measured states of the N qubits as N random bits.