  We produce and holographically measure entangled qudits encoded in transverse
spatial modes of single photons. With the novel use of a quantum state
tomography method that only requires two-state superpositions, we achieve the
most complete characterisation of entangled qutrits to date. Ideally, entangled
qutrits provide better security than qubits in quantum bit-commitment: we model
the sensitivity of this to mixture and show experimentally and theoretically
that qutrits with even a small amount of decoherence cannot offer increased
security over qubits.
