  We study the higher-order statistical properties of the Carnot cycle whose
working substance consists of a small, classical system. We show that the ratio
between the fluctuations of work and heat is given by an universal form
depending solely on the temperature ratio between the hot and cold heat baths.
Moreover, we show that the Carnot cycle provides the upper bound on this
fluctuation ratio for cycles consisting of quasistatic strokes. These results
serve as a guiding principle in the design and optimization of fluctuations in
small heat engines.
