Arbitrary quantum information is input. The information of a quantum two-state system is acquired as a qubit by performing a computation in consideration of a physical system. The acquired qubit is encrypted. A quantum system having signature information for guaranteeing that the qubit is really transferred from a sender to a recipient is added to the encrypted qubit. The qubit to which the quantum system having the signature information is added is further encrypted. In this manner, an arbitrary quantum state can be encrypted and transmitted without letting the sender and recipient share an entangled pair of qubits in advance.