Nonlinearity symmetry breaking for generating tunable quantum entanglement in semiconductor metasurfaces

Area of Science:

• Quantum optics
• Metasurfaces
• Nonlinear optics

Background:

• Tunable biphoton quantum entanglement is crucial for quantum technologies.
• Material symmetry in nonlinear optical tensors limits entanglement tunability.
• Asymmetric optical responses are key for advanced optical applications.

Purpose of the Study:

• To overcome symmetry constraints in generating tunable biphoton quantum entanglement.
• To demonstrate the use of symmetry breaking in nonlinear polarization via resonant metasurfaces.
• To experimentally realize continuous tuning of polarization entanglement.

Main Methods:

• Utilized structural-asymmetric semiconductor metasurfaces with [110] InGaP nanoresonators.
• Introduced symmetry breaking in nonlinear polarization through resonant metasurfaces.
• Adjusted pump wavelength to tune polarization entanglement.

Main Results:

• Achieved continuous tuning of polarization entanglement from partially entangled states to a Bell state.
• Observed pronounced spatial anti-correlations.
• Demonstrated an ultrahigh coincidence-to-accidental ratio of ≈7 × 10^4, surpassing existing semiconductor flat optics.

Conclusions:

• Symmetry breaking in nonlinear polarization via resonant metasurfaces enables tunable biphoton entanglement.
• This approach can be extended to tailor hyperentanglement.
• The developed nanoscale entanglement source offers superior performance for quantum applications.