Long-term stabilization of intensity-difference squeezing from four-wave mixing in rubidium vapor

Area of Science:

• Quantum Optics
• Nonlinear Optics

Background:

• Generating quantum states of light via off-resonance four-wave mixing in rubidium vapor is established.
• Achieving stable intensity difference squeezing (IDS) and quantum correlations over extended periods for quantum-light-based nonlinear optical spectroscopy and microscopy is challenging.

Purpose of the Study:

• To develop and validate a simple stabilization method for quantum light generation.
• To improve the consistency of intensity difference squeezing (IDS) and quantum correlations for extended timescales.

Main Methods:

• Implemented a stabilization technique combining active periodic laser frequency retuning with an automatic control algorithm.
• Quantitatively assessed factors influencing IDS level and squeezed light intensity.
• Validated the method over a 5-hour data acquisition period.

Main Results:

• Demonstrated a remarkably stable squeezing level of -7.8 dB.
• Achieved a >4× reduction in the standard deviation of the IDS level (from 0.46 dB to 0.10 dB).
• Enabled quantitative assessment of IDS reduction due to scattering in a polystyrene bead suspension.

Conclusions:

• The developed stabilization method significantly enhances the stability of quantum light generation.
• This approach enables applications requiring hours of squeezing stability, such as real-time monitoring of biological processes and chemical reactions.
• The method facilitates quantitative analysis of scattering effects in samples using quantum light techniques.