How can you increase the bounce height of a rubber ball?

What you must not do:

Travel to another planet.

Accelerate the rubber ball downwards.

Or let's put it this way: you are only allowed to release the rubber ball from a given height.

Which factors can be changed:

-Temperature of the rubber ball

-Ambient temperature

-Rubber compound

-geometric shape, but the volume must remain constant. (I'm quite sure that a sphere is the best solution.)

What properties would be required of the rubber or other materials used to make the rubber ball bounce higher? Manufacturing costs are not a factor.

My idea would be to use a material that converts the energy after impact back into kinetic energy without any frictional losses. However, this would also require adapting the floor…

Would it be advantageous if the rubber ball deformed more? Or could it be made so that the rubber ball converts the deformation energy even faster?