  We propose a scheme for perfect excitation of a single two-level atom by a
single photon in free space. The photon state has to match the time reversed
photon state originating from spontaneous decay of a two-level system. We
discuss its experimental preparation. The state is characterized by a
particular asymmetric exponentially-shaped temporal profile. Any deviations
from this ideal state limit the maximum absorption. Although perfect excitation
requires an infinite amount of time we demonstrate that there is a class of
initial one-photon quantum states which can achieve almost perfect absorption
even for a finite interaction time. Our results pave the way for realizing
perfect coupling between flying and stationary qubits in free space thus
opening a possibility for building scalable quantum networks.
