Modeling Quantum Noise in Nanolasers using Markov Chains

Fuente: arXiv
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Main Authors: Bundgaard-Nielsen, Matias, Lippi, Gian Luca, Mørk, Jesper
Format: Preprint
Published: 2025
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author Bundgaard-Nielsen, Matias
Lippi, Gian Luca
Mørk, Jesper
author_facet Bundgaard-Nielsen, Matias
Lippi, Gian Luca
Mørk, Jesper
contents The random nature of spontaneous emission leads to unavoidable fluctuations in a laser's output. This is often included through random Langevin forces in laser rate equations, but this approach falls short for nanolasers. In this paper, we show that the laser quantum noise can be quantitatively computed for a very broad class of lasers by starting from simple and intuitive rate equations and merely assuming that the number of photons and excited electrons only takes discrete values. While the approach has seen previous success, we here derive it rigorously from an open quantum system master equation, whereas it was previously introduced only on phenomenological grounds. We further show that in the many-photon limit, the model simplifies to Langevin equations. We perform an extensive comparison of different approaches for computing quantum noise in lasers, identifying the best approach for different system sizes, ranging from nanolasers to macroscopic lasers, and different levels of excitation, i.e., cavity photon number. In particular, we show that below the laser threshold, stochastic fluctuations in the numerical solution to the Langevin equations can drive populations to unphysical negative values, requiring the introduction of population bounds, which in turn skew the noise statistics, leading to inaccuracies. The Laser Markov Chain model, on the other hand, is accurate for all pump values and laser sizes when collective emitter effects are excluded.
format Preprint
id arxiv_https___arxiv_org_abs_2511_13622
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Modeling Quantum Noise in Nanolasers using Markov Chains
Bundgaard-Nielsen, Matias
Lippi, Gian Luca
Mørk, Jesper
Quantum Physics
Optics
The random nature of spontaneous emission leads to unavoidable fluctuations in a laser's output. This is often included through random Langevin forces in laser rate equations, but this approach falls short for nanolasers. In this paper, we show that the laser quantum noise can be quantitatively computed for a very broad class of lasers by starting from simple and intuitive rate equations and merely assuming that the number of photons and excited electrons only takes discrete values. While the approach has seen previous success, we here derive it rigorously from an open quantum system master equation, whereas it was previously introduced only on phenomenological grounds. We further show that in the many-photon limit, the model simplifies to Langevin equations. We perform an extensive comparison of different approaches for computing quantum noise in lasers, identifying the best approach for different system sizes, ranging from nanolasers to macroscopic lasers, and different levels of excitation, i.e., cavity photon number. In particular, we show that below the laser threshold, stochastic fluctuations in the numerical solution to the Langevin equations can drive populations to unphysical negative values, requiring the introduction of population bounds, which in turn skew the noise statistics, leading to inaccuracies. The Laser Markov Chain model, on the other hand, is accurate for all pump values and laser sizes when collective emitter effects are excluded.
title Modeling Quantum Noise in Nanolasers using Markov Chains
topic Quantum Physics
Optics
url https://arxiv.org/abs/2511.13622