Restoring Quantum Communication Efficiency over High Loss Optical Fibers

Area of Science:

• Quantum Information Science
• Quantum Communication
• Quantum Optics

Background:

• Quantum communication is limited by signal loss in optical fibers over 20 km.
• Transmissivity below 1/2 prevents reliable quantum state transfer.
• Quantum repeaters are typically required for long-distance quantum communication.

Purpose of the Study:

• To investigate the impact of signal memory effects on quantum communication.
• To develop schemes for unassisted quantum communication over arbitrarily long optical fibers.
• To explore entanglement-assisted communication strategies for extended distances.

Main Methods:

• Analyzing quantum signal transmission considering memory effects.
• Developing theoretical schemes for unassisted quantum communication.
• Formulating entanglement-assisted communication protocols.

Main Results:

• Unassisted quantum communication is feasible over arbitrarily long optical fibers by accounting for memory effects.
• A fixed positive qubit transmission rate can be achieved.
• Entanglement-assisted communication achieves rates comparable to the noiseless unassisted case.

Conclusions:

• Memory effects in quantum signals can be leveraged to overcome distance limitations in optical fiber communication.
• Novel schemes enable robust unassisted and entanglement-assisted quantum communication over extended ranges.
• This research paves the way for practical long-distance quantum networks without repeaters.