Abstract
The sensitivity properties of an SU(1,1) interferometer made of two cascaded parametric amplifiers, as well as of an ordinary SU(2) interferometer preceded by a squeezer and followed by an anti-squeezer, are theoretically investigated. Several possible experimental configurations are considered, such as the absence or presence of a seed beam, direct or homodyne detection scheme. In all cases we formulate the optimal conditions to achieve phase super-sensitivity, meaning a sensitivity overcoming the shot-noise limit. We show that for a given gain of the first parametric amplifier, unbalancing the interferometer by increasing the gain of the second amplifier improves the interferometer properties. In particular, a broader super-sensitivity phase range and a better overall sensitivity can be achieved by gain unbalancing.
Highlights
Estimating the phase of light is one of the most important tasks in optics
It is important to note that the decrease of defined by (Df) is not accompanied by an increase of DN, see equation (3), because the optical quantum state inside the interferometer is obviously not affected by the output anti-squeezer
We have studied the phase sensitivity properties of an SU(1,1) interferometer, considering the cases of both direct and homodyne detection at the output and taking into account internal and external losses as well as the detector noise
Summary
Several possible experimental configurations are considered, such as the the work, journal citation and DOI. In all cases we formulate the optimal conditions to achieve phase super-sensitivity, meaning a sensitivity overcoming the shotnoise limit. We show that for a given gain of the first parametric amplifier, unbalancing the interferometer by increasing the gain of the second amplifier improves the interferometer properties. A broader super-sensitivity phase range and a better overall sensitivity can be achieved by gain unbalancing
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