As we know, the correct sized icon:
* drawable-ldpi (120 dpi, Low density screen) - 36px x 36px * drawable-mdpi (160 dpi, Medium density screen) - 48px x 48px * drawable-hdpi (240 dpi, High density screen) - 72px x 72px * drawable-xhdpi (320 dpi, Extra-high density screen) - 96px x 96px
On Jelly Bean,
drawable-xxhdpi can be supported. So what’s the correct size icon?
- MDPI: 48×48
- HDPI: 72×72
- XHDPI: 96×96
- XXHDPI: 144×144
- XXXHDPI: 192×192
to create an icon for different densities, you should follow the 2:3:4:6:8 scaling ratio between the five primary densities (medium, high, x-high, xx-high, and xxx-high respectively)
This is a quote from a post on Google Plus https://plus.google.com/118292708268361843293/posts/ePQya3KsTjW by Nick Butcher
The gorgeous screen on the Nexus 10 falls into the XHDPI density
bucket. On tablets, Launcher uses icons from one density bucket up
 to render them slightly larger. To ensure that your launcher icon
(arguably your apps most important asset) is crisp you need to add a
144*144px icon in the drawable-xxhdpi or drawable-480dpi folder.
So, for the xxhdpi qualifier, you will need to create an icon of the size 144*144px for your launcher icon. You can either place it in the drawable-xxhdpi or the drawable-480dpi
EDIT: To add to the original answer to address cone of the comments by the OP.
As per this link: http://developer.android.com/guide/practices/screens_support.html#DesigningResources, alternative resources should be created using this ratio: 3:4:6:8 scaling ratio. However, if you are concerned about loosing quality with regards to your in-app drawable resource, consider using 9-patch images wherever possible. That will reduce or eliminate any loss of quality. The Android OS all by itself, does a remarkable job handling various screen sizes most of the time anyway.
As for the icon size 144*144px, create either of these two folder drawable-xxhdpi or the drawable-480dpi and place just your launcher icon of the said size in it. That should do it.
You need to add a 144*144px icon in the drawable-xxhdpi or drawable-480dpi folder.
For more information:-
Official G+ shows that xxhdpi is 480dpi:
Standart icon size in dip is 48 dip.
You might use this service for creation all size icons. (Set size – 48 dip, and other settings)