“…Quantum heat engines and cyclic refrigerators are presently under intensive study; see Humphrey and Linke (2005), Quan et al (2007), Deffner, Jarzynski, andCampo (2014), Pilgram, Sánchez, and López (2015), Campisi and Fazio (2016), Benenti et al (2017), Brandner, Bauer, andSeifert (2017), Alicki and Kosloff (2018), Josefsson et al (2018), Bhandari et al (2020), Majidi et al (2021), andRaja et al (2021). Experiments that are fully in the quantum regime have thus far been practically nonexistent, although there have been proposals addressing realistic setups (Abah et al, 2012;Karimi and Pekola, 2016).…”