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arXiv:2405.10555 · Physical Review A

Light with even Fock states from interference of Kerr-squeezed light

Ziv Abelson, Shimshon Bar-Ad

Published Oct 9, 2024• 0 citations
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Abstract

We demonstrate the generation of nonclassical light by destructive interference of identical Kerr-squeezed states. Perfect pairwise cancellation of amplitudes that contribute to odd Fock states results in light with only even Fock states, independent of the strength of the nonlinearity. The observability of this effect is only limited by the quality of the interferometer. In the low nonlinearity limit, the even-only state resembles a squeezed vacuum state, yet the even-odd oscillations persist when the nonlinearity is strong. The effect is also robust against deviations from the optimum relative phase of the input Kerr-squeezed states.

DOI
10.1103/physreva.110.043708

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We demonstrate the generation of nonclassical light by destructive interference of identical Kerr-squeezed states. Perfect pairwise cancellation of amplitudes that contribute to odd Fock states results in light with only even Fock states, independent of the strength of the nonlinearity. The observability of this effect is only limited by the quality of the interferometer. In the low nonlinearity limit, the even-only state resembles a squeezed vacuum state, yet the even-odd oscillations persist when the nonlinearity is strong. The effect is also robust against deviations from the optimum relative phase of the input Kerr-squeezed states.
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We propose a scheme to generate a displaced macroscopic superposition of phase squeezed coherent states by incorporating an optical parametric oscillator (OPO) and a nonlinear Kerr medium in a Mach-Zhender interferometer configuration. We show that the phase squeezed coherent state generated by the OPO evolves into a macroscopic superposition of phase squeezed coherent states on spending a specific amount of time inside a Kerr medium. The phase space displacement is achieved by the interference of the intense reference beam with the signal in the final beam splitter of the interferometer. The noise of the reference beam contaminating the signal is prevented by making this beam splitter highly reflective. We have calculated the photon number uncertainty of the outcoming beam and have shown that it is smaller than the usual amplitude squeezed coherent state's value.
One of the most promising applications for squeezed light is interferometry beyond the shot-noise limit (SNL). To date, only squeezed light generated by parametric down-conversion has been used to improve interferometer sensitivity. Remarkable results have been achieved with this approach, including applications to large-scale gravitational wave detectors. On the other hand, there exists a potentially more robust way to generate squeezed light, that is, using the optical Kerr effect. It occurs almost for free in optical fibers and requires no phase matching. However, no interferometer sensitivity enhancement has been demonstrated so far using this method. One of the reasons for that is that the uncertainty distribution of a Kerr-squeezed state in phase space is tilted with respect to the amplitude or phase quadratures. Additional obstacles include Raman and guided acoustic wave Brillouin scattering in fibers.
We show that a Kerr-nonlinear cavity coupled to an incoherently pumped two-level qubit can stabilize a nonclassical steady state with pronounced Wigner negativity. Without the qubit, two-photon drive and dissipation preserve photon-number parity and confine vacuum-initiated dynamics to the even-parity Fock subspace, preventing the emergence of odd-parity-induced central Wigner negativity. The qubit opens a frequency-selective injection channel into the odd-parity Fock subspace, while Kerr nonlinearity suppresses unwanted higher-order transitions, driving the system toward a steady state dominated by the single-photon Fock state that can approach a nearly pure state in the optimal regime. The resulting Wigner negativity remains robust over broad experimentally relevant loss and dephasing regimes, providing a route to the dissipative stabilization of nonclassical light in cavity quantum electrodynamics platforms.
The generation of nonclassical states of light with specified frequency-dependent squeezing by way of introducing a correlation between the phase and amplitude of the input field is considered. Three schemes for measuring amplitude fluctuations of the input beam, based on a nondemolition measurement of the intensity in a nonlinear cubic crystal, the effect of light rectification in a quadratic optical crystal, and the use of a non-degenerate optical parametric oscillator, are proposed. The maximum possible value of noise suppression is estimated for each scheme. The prospects for practical realization of the proposed method for generation of frequency-dependent squeezed states are discussed.