Polarization Engineering in Photonic Crystal Waveguides for Spin-Photon Entanglers

Area of Science:

• Quantum optics
• Condensed matter physics
• Nanophotonics

Background:

• Photonic crystal waveguides (PCWs) offer unique light-matter interaction control.
• Quantum dots (QDs) are promising solid-state emitters for quantum information processing.
• Symmetry in light-matter interactions is key for directional emission and quantum device functionality.

Purpose of the Study:

• To analyze the role of phase in local density of states (LDOS) for light-matter interactions in PCWs.
• To investigate how QD spin coupling to PCW modes influences interaction asymmetry.
• To demonstrate the potential for unidirectional emission and deterministic entangled photon generation.

Main Methods:

• Full analysis of projected local density of states (LDOS).
• Modeling quantum dot (QD) spin coupled to photonic crystal waveguide (PCW) modes.
• Investigating phase dependencies in light-matter coupling and quantum interference.

Main Results:

• Phase is critical for determining the symmetry of light-matter interactions.
• Asymmetric light-matter interactions lead to unidirectional emission.
• Suppression of quantum interference prevents dipole-induced reflection.
• A breakdown of the semiclassical dipole approximation is observed in spin-dependent systems.

Conclusions:

• Understanding phase in LDOS and QD spin is essential for designing PCW-based quantum devices.
• Asymmetric light-matter coupling enables deterministic entangled photon sources.
• The findings challenge semiclassical approximations in spin-dependent quantum optics.