Abstract
We present the solid-state quantum circuits that have been developed in order to implement quantum bits suitable for a quantum processor. These qubits are either based on the quantum state of a single particle (semiconductor qubits), or on the quantum state of the global circuit (superconducting qubits). We discuss more in detail the superconducting qubits, and present results on qubit manipulation and readout. We explain the main strategies used to improve and tio maintain quantum coherence.