# Resonant absorption by two-level systems
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## Jackle
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## Galperin
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## tutorials
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https://wp.optics.arizona.edu/opti511r/wp-content/uploads/sites/23/2016/01/HW9_2016.pdf
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https://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-974-fundamentals-of-photonics-quantum-electronics-spring-2006/lecture-notes/chapter6.pdf
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- thermodynamics
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http://home.thep.lu.se/~larsg/Site/SM2.pdf
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# Parents
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* QSNS universality - Leggett et al⏎