Massively parallel Hong-Ou-Mandel interference based on independent soliton microcombs

Area of Science:

• Quantum Optics and Photonics
• Quantum Information Science
• Optical Communications

Background:

• Hong-Ou-Mandel (HOM) interference is crucial for testing photon indistinguishability in quantum technologies.
• Scaling HOM interference to massively parallel optical channels is hindered by the lack of natural optical references for aligning laser pairs.

Purpose of the Study:

• To demonstrate high-visibility HOM interference across numerous parallel optical channels.
• To overcome alignment challenges for massively parallel quantum information processing.
• To explore the integration of quantum communication with classical wavelength division multiplexing.

Main Methods:

• Utilized two independently frequency post-aligned soliton microcombs (SMCs) to generate 50 parallel comb-teeth pairs of continuous-wave weak coherent photons.
• Developed fully frequency-stabilized SMCs with independent references for long-term alignment of comb-teeth pair frequencies.
• Adjusted the free spectral range beyond 100 kilohertz through perturbations in the soliton state for precise alignment.

Main Results:

• Achieved HOM interference with an average fringe visibility exceeding 46% across 50 parallel channels.
• Demonstrated long-term frequency alignment of all comb-teeth pairs using stabilized soliton microcombs.
• Verified the feasibility of constructing massively parallel quantum information channels.

Conclusions:

• The study successfully demonstrates a scalable method for generating high-visibility HOM interference using soliton microcombs.
• This approach integrates quantum information channels with classical wavelength division multiplexing, paving the way for practical large-scale quantum communication systems.