Phase noise in collective binary phase shift keying with Hadamard words

Area of Science:

• Quantum communication
• Optical communication systems
• Information theory

Background:

• Optical communication schemes often face limitations due to phase noise.
• Collective detection offers potential advantages over individual detection in certain regimes.
• Understanding information superadditivity is key for advancing classical communication over quantum channels.

Purpose of the Study:

• To analyze the impact of phase fluctuations on a collective detection scheme for binary coherent state symbols.
• To determine if the superadditivity of accessible information is preserved under phase noise.
• To compare the performance of collective detection with individual detection in the presence of phase noise.

Main Methods:

• Utilizing linear optics and photon counting for collective detection.
• Analyzing sequences of binary coherent state symbols.
• Mathematical modeling to assess spectral efficiency and information scaling with photon number.

Main Results:

• The scheme demonstrates qualitatively improved nonlinear scaling of spectral efficiency with mean photon number in the low-power regime compared to individual detection.
• This performance advantage, showing superadditivity of accessible information, is preserved when random phases fluctuate around a fixed reference.
• Phase fluctuations do not negate the benefits of collective detection for quantum channel communication.

Conclusions:

• Collective detection in optical communication is robust against phase fluctuations, preserving enhanced spectral efficiency.
• The superadditivity of accessible information in classical communication over quantum channels is demonstrated and maintained under specific phase noise conditions.
• This research highlights the potential of collective detection for future high-performance optical communication systems.