  We propose a way to realize a multiqubit tunable phase gate of one qubit
simultaneously controlling n target qubits with atoms in cavity QED. In this
proposal, classical pulses interact with atoms outside a cavity only, thus the
experimental challenge of applying a pulse to an intra-cavity single atom
without affecting other atoms in the same cavity is avoided. Because of
employing a first-order large detuning, the gate can be performed fast when
compared with the use of a second-order large detuning. Furthermore, the gate
operation time is independent of the number of qubits. This proposal is quite
general, which can be applied to various superconducting qubits coupled to a
resonator, NV centers coupled to a microsphere cavity or quantum dots in cavity
QED.
