Capacity estimation and verification of quantum channels with arbitrarily correlated errors

Area of Science:

• Quantum Information Science
• Quantum Communication
• Quantum Computing

Background:

• Quantum capacity is vital for quantum memories and communication.
• Correlated errors pose a significant challenge in estimating quantum capacity.
• Quantum repeaters require reliable methods to assess information transmission capabilities.

Purpose of the Study:

• To present a protocol for estimating a lower bound on quantum capacity.
• To address challenges posed by arbitrarily correlated errors.
• To provide a tool for testing quantum repeater performance and verifying channel performance.

Main Methods:

• The protocol estimates the one-shot quantum capacity using two measurement bases.
• A second version verifies the quantum capacity in real-time during data transmission or storage.
• The method utilizes all involved qubits as test qubits.

Main Results:

• The protocol provides a lower bound on quantum capacity, robust against correlated errors.
• Demonstrated applicability to quantum repeaters and channel performance verification.
• The method is asymptotically optimal for channels like the dephasing channel.

Conclusions:

• The presented protocol offers a practical and implementable approach to assess quantum channel performance.
• The method was successfully applied to a superconducting qubit experiment.
• This work contributes to advancing reliable quantum communication and memory technologies.