Figure 5
From: Quantum phase estimation using path-symmetric entangled states
(a) Generation of SOOS state via a conditional phase shift (CPS) operation. Each single-mode squeezed vacuum state is injected into a CPS operation setup. Ancillary qubits are entangled in polarization (H, V) and path (u, d) modes. LO stands for local squeezing operation 
. (b) Generation of QOOQ state via a successive application of the coherent operation 
with ϕk = 2πk/N. NOON state is first injected into the coherent operation setups. The coherent operation 
is implemented with three beam splitters. Two beam splitters are highly reflective whereas one beam splitter is highly transmissive. The phase ϕk is a control parameter of strong coherent light.
