Quantum transistor with superconducting artificial atoms

Controlling quantum information flow inside a quantum processor can be a desirable task in a scenario where the gate fidelity depends on the qubit in which the operation is implemented. This leads to the necessity of developing a quantum device that controls how the information is switched between different parts of such processors. In this paper, we introduce the smallest quantum transistor for superconducting quantum processors, constituted of collector and emissor qubits, and the transistor gate controlled by the state of a single qubit. First, we show how the effective interaction between the collector and emissor depends on the gate state, which is used as a quantum-state switch, and how the multilevel characteristic of artificial atoms affects the effective collector-emissor coupling strength. Then high fidelity control of quantum information flow is verified. The quantum device presented meets a potential application in quantum information control in superconducting circuits.