Raman coherence beats from entangled polarization eigenstates in InAs quantum dots

Area of Science:

• Quantum optics
• Solid-state physics
• Materials science

Background:

• Self-assembled quantum dots (QDs) are crucial for quantum information technologies.
• Understanding exciton dynamics in QDs is essential for device applications.
• Homodyne detection offers phase-sensitive measurements of quantum phenomena.

Purpose of the Study:

• To investigate the temporal dynamics of optically induced Raman coherence in InAs/GaAs quantum dots.
• To measure the fine-structure splitting (FSS) and decoherence rates of entangled exciton polarization states.
• To demonstrate the utility of homodyne-detected transient four-wave mixing for probing quantum coherence.

Main Methods:

• Utilized transient four-wave mixing (TFWM) spectroscopy with homodyne detection.
• Applied TFWM to InAs/GaAs self-assembled quantum dots.
• Analyzed temporal oscillations in the homodyne signal to extract coherence dynamics.

Main Results:

• Observed temporal oscillations in the TFWM response, attributed to Raman coherence.
• Identified oscillations arising from two entangled polarization eigenstates of the exciton.
• Successfully measured the fine-structure splitting (FSS) of the exciton states.
• Quantified the decoherence rate of the entangled polarization states.

Conclusions:

• Homodyne detection allows sensitive tracking of nonradiative quantum coherence.
• TFWM is a powerful technique for measuring FSS in quantum dots, even when it's smaller than inhomogeneous broadening.
• The study provides insights into exciton decoherence mechanisms in self-assembled quantum dots.