Optimum Mixed-State Discrimination for Noisy Entanglement-Enhanced Sensing

Area of Science:

• Quantum optics
• Quantum sensing
• Quantum information science

Background:

• Quantum metrology offers enhanced sensor performance using nonclassical resources like entanglement.
• Environmental noise and loss typically degrade these nonclassical resources, limiting sensor advantages.
• Quantum illumination (QI) is a robust scheme where entanglement-enhanced sensing advantages persist despite initial entanglement loss.

Purpose of the Study:

• To develop an optimal quantum receiver for quantum illumination (QI) that overcomes limitations of previous implementations.
• To investigate the application of sum-frequency generation (SFG) for practical quantum sensing receivers.
• To achieve performance close to theoretical quantum limits in realistic noisy environments.

Main Methods:

• Applying sum-frequency generation (SFG) to the problem of optimum multimode Gaussian-mixed-state discrimination.
• Analyzing and numerically evaluating the performance of the SFG-based quantum receiver for QI.
• Augmenting the SFG receiver with a feedforward (FF) mechanism to approach the Helstrom bound.

Main Results:

• The SFG receiver successfully saturates the quantum Chernoff bound for QI.
• The feedforward-augmented SFG (FF-SFG) receiver achieves performance approaching the Helstrom bound at low signal brightness.
• Demonstrated the practical feasibility of achieving near-optimal quantum sensing performance.

Conclusions:

• Sum-frequency generation provides a viable method for implementing optimal quantum receivers in QI.
• The FF-SFG receiver significantly advances the practical realization of quantum-enhanced technologies.
• This work paves the way for improved quantum-enhanced imaging, radar, communication, and tomography.