Precise control of squeezing angle to generate 11 dB entangled state.

Area of Science:

• Quantum Physics
• Quantum Optics

Background:

• Quantum correlations in continuous-variable entangled states are sensitive to relative phases during preparation, transmission, and detection.
• Precise control over these phases is crucial for optimizing the strength of quantum correlations.

Purpose of the Study:

• To experimentally and theoretically demonstrate the precision of relative phases affecting quadrature correlations.
• To establish robust phase-locking methodologies for stabilizing quantum states.

Main Methods:

• Development of three phase-locking methodologies: ultralow noise (RAM) control loops for DOPAs, difference DC locking for squeezed beams, and DC-AC joint locking for BHDs.
• Stabilization of relative phase differences to minimize phase noise.

Main Results:

• Phase-locking loops achieved total phase noise levels of 9.7±0.32/11.1±0.36 mrad.
• Relative phase deviations were controlled within -35 to 35 mrad.
• Enhanced correlations in amplitude and phase quadratures to -11.1 and -11.3 dB, respectively.
• Demonstrated a broadband squeezing bandwidth of up to 100 MHz.

Conclusions:

• The established phase-locking techniques effectively control relative phase deviations in continuous-variable entangled states.
• The enhanced quantum correlations and broadband squeezing bandwidth represent a significant resource for quantum information processing and precision measurement applications.