Quantum repeater systems and apparatus for quantum communication. In one aspect, a system includes a quantum signal receiver configured to receive a quantum field signal; a quantum signal converter configured to: sample quantum analog signals from a quantum field signal received by the quantum signal receiver; encode sampled quantum analog signals as corresponding digital quantum information in one or more qudits, comprising applying a hybrid analog-digital encoding operation to each quantum analog signal and a qudit in an initial state; decode digital quantum information stored in the one or more qudits as a recovered quantum field signal, comprising applying a hybrid digital-analog decoding operation to each qudit and a quantum analog register in an initial state; a quantum memory comprising qudits and configured to store digital quantum information encoded by the quantum signal converter; and a quantum signal transmitter configured to transmit the recovered quantum field signal.

Migration of quantum services from quantum computing devices to quantum simulators is disclosed herein. In one example, a quantum computing device executes a migration service that receives a system stress indicator from a system monitor that tracks a status of the quantum computing device and/or a status of qubits maintained by the quantum computing device. The migration service determines, based on the system stress indicator, that a quantum service running on the quantum computing device is to be migrated. Upon determining that the quantum service is to be migrated, the migration service retrieves a QASM file that contains quantum programming instructions defining the quantum service. The QASM file is then transmitted to a quantum simulator running on a classical computing device for failover execution. In some examples, the classical computing device then executes a simulated quantum service within the quantum simulator based on the QASM file.

A device comprises a data quantum bit, a first quantum bit coupler, a second quantum bit coupler, and an auxiliary quantum bit. The first quantum bit coupler is coupled to the data quantum bit. The second quantum bit coupler is coupled to the first quantum bit coupler. The auxiliary quantum bit is coupled to the second quantum bit coupler. The first quantum bit coupler is configured to operate in a state to suppress interaction between the data quantum bit and the auxiliary quantum bit. The first quantum bit coupler and the second quantum bit coupler are each configured to operate in a respective state to enable interaction between the data quantum bit and the auxiliary quantum bit and entangle a state of the data quantum bit with a state of the auxiliary quantum bit.

The present disclosure provides a quantum-dot ligand, a quantum-dot catalyst and a quantum-dot device. The quantum-dot ligand includes: a first ligand having a first group and a second group and a second ligand having an inorganic ion, in which a coordination bond is formed between the first group and a surface of a quantum dot, a hydrogen bond is formed between the second group and a hydroxyl group; and a coordination bond is formed between the inorganic ion and the surface of the quantum dot. The quantum-dot catalyst of the present disclosure can enhance a catalytic activity of the quantum dots and improve the catalytic performance.