Entanglement between a Diamond Spin Qubit and a Photonic Time-Bin Qubit at Telecom Wavelength

Area of Science:

• Quantum physics
• Quantum information science
• Optics and photonics

Background:

• Quantum entanglement is a fundamental quantum mechanical phenomenon.
• Nitrogen-vacancy (NV) electron spin qubits are promising solid-state qubits.
• Telecom-band photons are ideal for long-distance quantum communication via optical fibers.

Purpose of the Study:

• To establish quantum entanglement between an NV electron spin qubit and a telecom-band photonic qubit.
• To demonstrate the feasibility of transferring quantum entanglement to the telecom band.
• To pave the way for integrated quantum networks.

Main Methods:

• Generating entanglement between a spin qubit and a visible-light photonic qubit (637 nm).
• Utilizing photonic quantum frequency conversion to shift the photon's wavelength to the telecom band (1588 nm).
• Characterizing the entangled state using correlation measurements in various bases.

Main Results:

• Successfully generated and verified quantum entanglement between the NV spin qubit and the telecom-band photon.
• Achieved a lower bound for the Bell state fidelity of ≥0.77±0.03.
• Demonstrated the transfer of entanglement to the 1588 nm telecom wavelength.

Conclusions:

• This work represents a significant advancement in quantum communication.
• The developed technique is crucial for building scalable quantum networks using existing fiber infrastructure.
• Enables the integration of solid-state qubits with long-range quantum communication channels.