  Photonic quantum information processing schemes, such as linear optics
quantum computing, and other experiments relying on single-photon interference,
inherently require complete photon indistinguishability to enable the desired
photonic interactions to take place. Mode-mismatch is the dominant cause of
photon distinguishability in optical circuits. Here we study the effects of
photon wave-packet shape on tolerance against the effects of mode-mismatch in
linear optical circuits, and show that Gaussian distributed photons with large
bandwidth are optimal. The result is general and holds for arbitrary linear
optical circuits, including ones which allow for post-selection and classical
feed-forward.
