Observing quantum coherence from photons scattered in free-space.

Area of Science:

• Quantum Information Science
• Optics and Photonics
• Quantum Communication

Background:

• Quantum channels in free-space typically require direct line-of-sight.
• Existing photon-encoding methods (polarization, spatial modes) fail with scattered photons.
• This limits quantum mechanics tests and quantum technologies in open environments.

Purpose of the Study:

• To develop a method for transferring and recovering quantum coherence from scattered, non-line-of-sight photons.
• To enable non-line-of-sight quantum communication and enhance low-light imaging/ranging.
• To overcome limitations of current free-space quantum channel technologies.

Main Methods:

• Utilized a multimode and imaging interferometer for time-bins to analyze scattered photons.
• Employed an 8x8 single-photon-detector array for photon detection.
• Demonstrated quantum coherence transfer and recovery from non-line-of-sight photons.

Main Results:

• Achieved high time-bin visibility (95%) for scattered photons across wide scattering angles (-45° to +45°).
• Resolved and tracked images with the detector array within a 0.5° field of view.
• Validated two novel applications: non-line-of-sight quantum communication and enhanced low-light imaging/ranging.

Conclusions:

• The developed method successfully transfers and recovers quantum coherence from scattered photons.
• This breakthrough enables non-line-of-sight quantum communication with background suppression.
• The technique offers enhanced contrast for low-light imaging and laser ranging in high-background conditions.
• This research opens new avenues for quantum sensing, imaging, and communication in free-space environments.