Take your current logo and double the resolution (144 dpi [dots per inch]). The document size width and height do not change but the pixel dimension will change to double it’s normal size.
Rename the logo with @2x: logo.png will be
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3) Then read up on Retina.js:
imulus.github.io/retinajs/
and utilize it (can be placed in /js/ directory in templates/rt_lumiere/ and then linked to via index.php file.)
Seems the best route from what I can see (I have no experience with this though). You can post for additional support via our forum if you'd like.