  Distributed computing is a fastest growing field -- enabling virtual
computing, parallel computing, and distributed storage. By exploiting the
counterfactual techniques, we devise a distributed blind quantum computation
protocol to perform a universal two-qubit controlled unitary operation for any
input state without using preshared entanglement and without exchanging
physical particles between remote parties. This distributed protocol allows Bob
to counterfactully apply an arbitrary unitary operator to Alice's qubit in
probabilistic fashion, without revealing the operator to her, using a control
qubit -- called the counterfactual concealed telecomputation (CCT). It is shown
that the protocol is valid for general input states and that single-qubit
unitary teleportation is a special case of CCT. The quantum circuit for CCT can
be implemented using the (chained) quantum Zeno gates and the protocol becomes
deterministic with simplified circuit implementation if the initial composite
state of Alice and Bob is a Bell-type state.
