引用:

A quantum is the smallest possible measurable amount of something. The most utterly tiny amount that makes the difference between something 'being something' and not. In scientific terms, it's generally considered to be an atom.

The 'Quantum of Solace' was explained as being that small, practically immeasurable spark of compassion, love or feeling that kept Philip Masters alive inside while his wife was so horrifically callous towards him.

As long as there was that Quantum of Solace, there was something between them. When she finally crushed that tiny spark, Rhoda killed the connection between her and her husband. That's what empowered him to leave his wife utterly penniless in an unfriendly community - practically driving her to prostitution before a rich Canadian rescued her (and it is Rhoda and her second husband that Bond meets at the conclusion of this story.)