Interference of Single Photons Emitted by Entangled Atoms in Free Space

Area of Science:

• Quantum optics
• Quantum information science
• Atomic physics

Background:

• Entanglement is crucial for quantum information processing and atomic ensemble optical properties.
• Controlled emission and absorption from small numbers of entangled emitters in free space remain largely unobserved.

Purpose of the Study:

• To demonstrate control over single-photon emission rates from entangled atoms in free space.
• To establish a method for optically determining the degree of entanglement between atoms.

Main Methods:

• Utilizing a pair of distant, entangled atoms.
• Modulating the optical path length between the atoms.
• Measuring single-photon emission rates and interference phase evolution.

Main Results:

• Controlled modulation of single-photon emission rate with V=0.27±0.03, directly linked to atomic entanglement (concurrence C_{ρ}=0.31±0.10).
• Developed a fully optical method for quantifying entanglement using emission rates and population measurements.
• Observed high sensitivity in interference phase evolution.

Conclusions:

• Demonstrated optical control and measurement of entanglement in a free-space atomic system.
• The presented scheme offers a novel approach for determining entanglement and has potential applications in high-precision gradient sensing.