  We propose a passively self-error-rejecting single-qubit transmission scheme
for an arbitrary polarization state of a single qubit over a collective-noise
channel, without resorting to additional qubits and entanglement. By splitting
a single qubit into some wavepackets with some Mach-Zehnder interferometers, we
can obtain an uncorrupted state with a success probability approaching 100% via
postselection in different time bins, independent of the parameters of
collective noise. It is simpler and more flexible than the schemes utilizing
decoherence-free subspace and those with additional qubits. One can directly
apply this scheme to almost all quantum communication protocols based on single
photons or entangled photon systems against a collective noise.
