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RESEARCH PRODUCT

Squeezing induced by spontaneous rotational symmetry breaking

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In this communication we study in depth the phenomenon of quadrature squeezing generated via spontaneous rotational symmetry breaking discussed for the first time in [1]. The idea can be put in short as follows. Consider a degenerate optical parametric oscillator (DOPO) tuned to the first family of transverse modes at the signal frequency, and having perfectly spherical mirrors. When pumped above threshold with a Gaussian beam and within a classical description, it is easy to show that a TEM 10 mode with an arbitrary orientation (measured by θ at Fig. 1) emerges at the subharmonic, hence breaking the rotational symmetry of the system in the transverse plane. Quantum effects are then quite intuitive: as any orientation is allowed, quantum noise is able to randomly rotate the generated pattern; this implies an indefiniteness in the angular orientation of the TEM 10 mode, what (invoking now the uncertainty principle) may lead to the perfect determination of its orbital angular momentum, which in this case coincides with the π/2 phase shifted TEM 10 mode orthogonal to the macroscopically generated one. Thus, perfect noise reduction is expected in the phase quadrature of this classically “empty” TEM 10 mode irrespectively of the pump level.