Patent ID: 8897449

Claim:
A quantum computing method comprising: receiving an encrypted state from a correspondent; receiving a control message from the correspondent; storing the encrypted state in a quantum register; applying a quantum circuit to the encrypted state to produce an encrypted output state, the quantum circuit comprising a sequence of operations that manipulates the quantum register, wherein the sequence of operations includes: a unitary operation parameterized by a control message from the correspondent; and an operation that produces encryption-key-update information; wherein the sequence of operations uses an auxiliary quantum state as input, the auxiliary quantum state includes an auxiliary qubit, the quantum register includes a register qubit, and applying the sequence of operations includes: applying a first gate to the auxiliary qubit and the register qubit; after applying the first gate: measuring the register qubit to obtain the encryption-key-update information; and applying a second gate to the auxiliary qubit, wherein the second gate is parameterized by the control message; sending the encrypted output state to the correspondent; and sending the encryption-key-update information to the correspondent.