Encrypted Qubits can be Cloned

Abstract: We show that encrypted cloning of unknown quantum states is possible. Any number of encrypted clones of a qubit can be created through a unitary transformation, and each of the encrypted clones can be decrypted through a unitary transformation. The decryption of an encrypted clone consumes the decryption key, i.e., only one decryption is possible, in agreement with the no-cloning theorem. A possible application of encrypted cloning is to enable encrypted quantum multi-cloud storage. Beyond applications in cryptography, encrypted cloning could provide a form of redundancy, parallelism, fault tolerance or scalability where direct duplication is forbidden by the no-cloning theorem.