  A quantum cellular network with a qubit and ancilla bits in each cell is
proposed. The whole circuit works only with the help of external optical pulse
sequences. In the operation, some of the ancilla bits are activated, and
autonomous single- and two-qubit operations are made. In the sleep mode of a
cell, the decoherence of the qubit is negligibly small. Since only two cells at
most are active at once, the coherence can be maintained for a sufficiently
long time for practical purposes. A device structure using a quantum dot array
with possible operation and measurement schemes is also proposed.
