  Due to their strong and tunable interactions, Rydberg atoms can be used to
realize fast two-qubit entangling gates. We propose a generalization of a
generic two-qubit Rydberg-blockade gate to multi-qubit Rydberg-blockade gates
which involve both many control qubits and many target qubits simultaneously.
This is achieved by using strong microwave fields to dress nearby Rydberg
states, leading to asymmetric blockade in which control-target interactions are
much stronger than control-control and target-target interactions. The
implementation of these multi-qubit gates can drastically simplify both quantum
algorithms and state preparation. To illustrate this, we show that a 25-atom
GHZ state can be created using only three gates with an error of 7.8%.
