Low-noise quantum frequency down-conversion of indistinguishable photons

Area of Science:

• Quantum optics
• Solid-state physics
• Quantum information science

Background:

• Indistinguishable single photons are essential for quantum communication and computing.
• Quantum frequency conversion is a key technique for interfacing photonic systems operating at different wavelengths.

Purpose of the Study:

• To demonstrate quantum frequency down-conversion of single photons from 904 nm to the telecom C-band (1557 nm).
• To verify the preservation of single-photon indistinguishability after the down-conversion process.

Main Methods:

• Experimental realization of quantum frequency down-conversion using an InAs/GaAs quantum dot.
• Hong-Ou-Mandel (HOM) interference measurements before and after down-conversion.
• Monte-Carlo simulations to analyze HOM experiments, considering time delays and signal-to-background ratio.
• Estimation of spectral diffusion impact on photon indistinguishability.

Main Results:

• Successful down-conversion of single photons from 904 nm to 1557 nm with high efficiency (> 30%).
• HOM interference measurements confirmed no loss of visibility after down-conversion.
• Simulations validated experimental results and quantified the impact of spectral diffusion.

Conclusions:

• The quantum frequency down-conversion process is noise-free and highly efficient.
• The demonstrated scheme is a promising source for generating indistinguishable single photons at telecom wavelengths.
• This work facilitates the integration of quantum dot sources with existing telecom infrastructure.