Entanglement Swapping with Semiconductor-Generated Photons Violates Bell's Inequality.

Area of Science:

• Quantum Information Science
• Solid-State Physics
• Optics

Background:

• Entangled photon pairs are crucial for quantum communication protocols.
• Semiconductor quantum dots offer deterministic generation of entangled photons.
• Entanglement swapping is a key technique for extending quantum network reach.

Purpose of the Study:

• To demonstrate entanglement swapping between two photon pairs emitted by a single semiconductor quantum dot.
• To verify the successful generation of a specific entangled state (Bell state Ψ⁺).
• To assess the fidelity and quantum nature of the generated entangled state.

Main Methods:

• Utilizing a single semiconductor quantum dot as a source of entangled photon pairs.
• Performing a joint Bell state measurement on one photon from each pair.
• Characterizing the generated entangled state using fidelity measurements and Bell inequality tests.

Main Results:

• Successfully achieved entanglement swapping between two photon pairs from a single quantum dot.
• Generated the Bell state Ψ⁺ with a high fidelity of 0.81±0.04.
• Demonstrated violation of the CHSH and Bell inequalities, confirming genuine entanglement.

Conclusions:

• The demonstrated entanglement swapping is a significant step towards scalable quantum networks.
• The photon source's compatibility with atomic quantum memory frequencies facilitates hybrid quantum repeater development.
• This work paves the way for practical quantum communication and distributed quantum computing.