Demonstration of coherent-state discrimination using a displacement-controlled photon-number-resolving detector

Area of Science:

• Quantum information science
• Quantum optics
• Quantum communication

Background:

• Distinguishing between coherent states is crucial for quantum information processing.
• Standard homodyne detection is a common but limited method for this task.
• Optimizing quantum measurement is key to advancing quantum technologies.

Purpose of the Study:

• To introduce and experimentally validate a novel measurement scheme for enhanced discrimination of two coherent states.
• To compare the performance of the new scheme against the optimal Gaussian measurement (homodyne detection).
• To assess the utility of the non-Gaussian detector in continuous-variable quantum key distribution (CV-QKD).

Main Methods:

• Implementing a measurement scheme involving a displacement operation.
• Utilizing a photon-number-resolving detector for state discrimination.
• Theoretical analysis of detector optimality within Gaussian operations.
• Experimental comparison with homodyne detection in a CV-QKD setup.

Main Results:

• The proposed measurement scheme experimentally outperforms the standard homodyne detector.
• The homodyne detector is proven to be optimal among all Gaussian operations.
• The non-Gaussian detector demonstrates superior performance in a CV-QKD scheme compared to homodyne detection.

Conclusions:

• A novel, high-performance measurement scheme for coherent state discrimination has been experimentally realized.
• The developed non-Gaussian detector offers significant advantages over traditional Gaussian methods for quantum communication tasks.
• This work paves the way for more robust and secure quantum key distribution protocols.