Superconducting qubits

From a physicist's standpoint, the most interesting part of quantum computing research may well be the possibility to probe the boundary between the quantum and the classical worlds. The more are the structures involved, the better. So far, the most macroscopic qubit prototypes that have been studied in the laboratory are certain kinds of superconducting qubits. To get a feeling for how these systems can be, the states of flux qubits which are brought in a quantum superposition corresponds to currents composed of as much as 10^5-10^6 electrons flowing in opposite directions in a superconducting loop. Non-superconducting qubits realized so far are all essentially microscopic.