Optical Zeno Gate and Bounds for Fault Tolerant Operations

Patrick Leung
University of Queensland

Quantum information processing requires universal two-qubit entangling
gates. Linear optical two-qubit quantum gates are inherently
nondeterministic and a large number of photons and gate operations are
required to implement a near deterministic two-qubit gate. The resource
requirement remains high despite a continuous in reducing it. A possible
solution to this problem is the optical quantum Zeno gate suggested by
Franson and co workers (PRA 70, 062302, 2004). This gate uses passive two
photon absorption to suppress gate failure events associated with photon
bunching at the linear optical elements, using the quantum Zeno effect.
With ideal absorbers, the gate operates deterministically and thus
eliminates the resource requirement problem. In this seminar, I will first
discuss the mechanism and performance of the Zeno gate with lossy
absorbers and propose its use in building qubit clusters. I will then show
how quantum teleportation technique can improve the Zeno gate, as well as
how mode-mismatch and detector inefficiency affect its performance.
Results on the lower bound estimates on the mode overlap and 1-photon to
2-photon transmission ratio, for which fault tolerant operation would be
possible, will be presented.