  Despite an apparent progress in implementing individual solid-state qubits,
there have been no experimental reports so far on multi-bit gates required for
building a real quantum computer. Here we report a new circuit comprising two
coupled charge qubits. Using a pulse technique, we coherently mix quantum
states and observe quantum oscillations whose spectrum reflects interaction
between the qubits. Our results demonstrate the feasibility of coupling of
multiple solid-state qubits and indicate the existence of entangled two-qubit
states.
