Titanium-based transition-edge photon number resolving detector with 98% detection efficiency with index-matched...

Area of Science:

• Quantum optics
• Superconducting devices
• Photon detection

Background:

• Photon number resolving detectors are crucial for quantum information processing.
• Existing detectors often face trade-offs between efficiency, resolution, and speed.
• Fiber-coupled detectors can suffer from wavelength-dependent efficiency due to optical interference.

Purpose of the Study:

• To develop a photon number resolving detector with high detection efficiency and resolution.
• To minimize wavelength-dependent efficiency in fiber-coupled systems.
• To achieve the highest system detection efficiency reported for the 850 nm wavelength range.

Main Methods:

• Fabrication of a titanium superconducting transition edge sensor (TES) integrated into an optical cavity.
• Direct fiber coupling with a reduced gap (approx. 300 nm) to minimize sensitive area and heat capacity.
• Characterization of detector performance, including efficiency, photon number resolution, and wavelength dependence.

Main Results:

• Achieved high photon number resolution of 0.42 eV.
• Maintained high detection efficiency and signal response speed.
• Reduced wavelength-dependent efficiency to less than 1% through the optimized coupling design.
• Demonstrated a record system detection efficiency of 98%±1% at approximately 850 nm.

Conclusions:

• The developed detector overcomes previous limitations in photon detection technology.
• The novel fiber coupling method significantly improves efficiency and reduces interference.
• This high-performance detector is a significant advancement for quantum technologies operating at 850 nm.