Parity detection achieves the Heisenberg limit in interferometry with coherent mixed with squeezed vacuum light

The interference between coherent and squeezed vacuum light effectively produces path entangled N00N states with very high fidelities. We show that the phase sensitivity of the above interferometric scheme with parity detection saturates the quantum Cramer-Rao bound, which reaches the Heisenberg limit when the coherent and squeezed vacuum light are mixed in roughly equal proportions. For the same interferometric scheme, we draw a detailed comparison between parity detection and a symmetric-logarithmicderivative- based detection scheme suggested by Ono and Hofmann. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft