Non-Hermitian Sensing in Photonics and Electronics: A Review

Area of Science:

• Quantum physics and condensed matter theory
• Photonics and electronics engineering

Background:

• Non-Hermitian Hamiltonians are gaining interest, particularly in optics and electronics.
• Real eigenvalues in non-Hermitian systems enable novel sensing applications.
• Exceptional points (EPs) in 2x2 non-Hermitian matrices exhibit square-root dependence of eigenvalue splitting on parameters, enabling high-sensitivity sensors.

Purpose of the Study:

• To review the fundamental principles of parity-time (PT)-symmetric and anti-PT-symmetric Hamiltonians in photonics and electronics.
• To investigate the impact of noise on non-Hermitian systems.
• To present recent advancements and solutions for overcoming noise limitations and highlight sensing applications.

Main Methods:

• Theoretical review of non-Hermitian Hamiltonians and exceptional points.
• Analysis of eigenvalue splitting and sensitivity dependence on perturbations (n-th root for higher-order EPs).
• Investigation of noise influence and exploration of mitigation strategies.

Main Results:

• Exceptional points provide theoretically infinite sensitivity near the EP, enabling high-performance sensors.
• Higher-order exceptional points offer n-th root dependence of eigenfrequency splitting.
• Exceptional sensitivity to external parameters also leads to significant noise susceptibility.

Conclusions:

• Non-Hermitian systems, particularly at exceptional points, offer unprecedented sensitivity for sensing.
• Addressing noise is crucial for practical applications of non-Hermitian sensors.
• Ongoing research is developing innovative solutions and demonstrating outstanding results in non-Hermitian photonics and electronics for sensing.