Phase-Tuned Entangled State Generation between Distant Spin Qubits.

Area of Science:

• Quantum Information Science
• Condensed Matter Physics
• Quantum Optics

Background:

• Quantum entanglement is crucial for quantum networks, enabling secure communication and computation.
• Distributing entanglement over long distances is a key challenge in building scalable quantum networks.

Purpose of the Study:

• To demonstrate optically generated quantum entanglement between distant electron spin qubits in semiconductor quantum dots.
• To develop a protocol for reliable entanglement distribution via photonic channels.

Main Methods:

• Utilizing spin-photon entanglement within a trionic Λ system.
• Implementing quantum erasure to remove path information of Raman photons.
• Measuring single Raman photons to project distant spin qubits into a joint quantum state.
• Employing an interferometrically stabilized and tunable relative phase.

Main Results:

• Achieved quantum entanglement between electron spin qubits in two distant semiconductor quantum dots.
• Reported an average Bell-state fidelity of 61.6±2.3% for |ψ^{(+)}⟩ and |ψ^{(-)}⟩ states.
• Established a record entanglement generation rate of 7.3 kHz between distant qubits.

Conclusions:

• The study successfully demonstrates a viable method for generating and distributing quantum entanglement between distant qubits.
• The achieved entanglement generation rate and fidelity represent significant progress towards practical quantum networks.