Time-resolved single-photon detection by femtosecond upconversion.

Area of Science:

• Quantum Optics
• Photonics
• Quantum Information Processing

Background:

• Precise timing measurements are crucial for advancing photonic quantum information processing.
• Existing single-photon detection methods often lack the required femtosecond temporal resolution.
• Ultrafast sum-frequency generation (SFG) offers a potential pathway for enhanced temporal resolution.

Purpose of the Study:

• To demonstrate a time-resolved single-photon detection technique with femtosecond measurement capability.
• To achieve high temporal resolution for infrared photon detection.
• To apply this technique for characterizing nonlinear optical crystals and analyzing entangled photon correlations.

Main Methods:

• Employed noncollinear broadband upconversion using periodically poled MgO-doped stoichiometric lithium tantalate.
• Utilized an ultrafast pump laser and a Silicon single-photon counter for detection.
• Achieved temporal resolution of approximately 150 femtoseconds (fs).

Main Results:

• Successfully mapped the generation efficiency profile of a periodically poled KTiOPO(4) crystal with millimeter resolution.
• Demonstrated the capability to assess local grating quality within the crystal.
• Performed two-photon coincidence measurements, directly showing time anticorrelation in entangled photons.

Conclusions:

• The developed time-resolved single-photon detection technique provides essential femtosecond timing resolution for quantum optics.
• This method enables detailed characterization of nonlinear optical materials and analysis of quantum correlations.
• It advances the capabilities for manipulating and measuring single photons in quantum information processing applications.