Optical zeno gate: bounds for fault tolerant operation

In principle the Zeno effect controlled-sign gate of Franson et al (2004 Phys. Rev. A 70 062302) is a deterministic two-qubit optical gate. However, when realistic values of photon loss are considered its fidelity is significantly reduced. Here we consider the use of measurement based quantum processing techniques to enhance the operation of the Zeno gate. With the help of quantum teleportation, we show that it is possible to achieve a Zeno CNOT gate (GC-Zeno gate) that gives (near) unit fidelity and moderate probability of success of 0.8 with a two-photon to one-photon absorption ratio kappa = 10(4). We include some mode-mismatch effects and estimate the bounds on the mode overlap and. for which fault tolerant operation would be possible.