Heralding an Arbitrary Decoherence-Free Qubit State

We present an optical device which is capable of heralding a variety of DFS states which protect against collective noise. Specifically, it can prepare all three basis states which span a DFS qutrit as well as an arbitrarily encoded DFS qubit state. We also discuss an interferometric technique for determining the amplitudes associated with an arbitrary encoding. The heralded state may find use in coherent optical systems which exhibit collective correlations.