How can I refine the edges between colors?

Question

I have an image with pixelated edges and i want to make those edges sharper so that you dont notice them at 100% zoom. I tried the sharpen tool but it does not do what I want.
In this sample image, I manually refined the left half of the pixelated diagonal line.
(The top right is what I want to change so that it looks like the part in the bottom left, which I did manually)

Answer 1

I think you miss understand what sharper means. It will not add pixels to remove stair-stepping. If anything it would make it more pronounced.
A blur will blend the two colors together to make it look like there is no edge, So that would not really work either.
Does this image have to be a certain size? Reducing the final print size will make it look sharper and less stair-stepped. But none the less they will still be there.
The new algorithm that will be in the next version of photoshop will help with this issue, but still does not totally solve it.
@all new users,
And this is why it is always best to start with the highest resolution possible, so you don't run into this issue.
@Alex,
You could try one of the algorithm's for upsampling and see if they help, try one, undo try the next and so on. No promises, but maybe one of them will be worth settling on.
If you know that the area is a solid color, you could use the pen tool to create the edge then fill the center with that color, thats the only way I can think of to recreate that area with a sharp edge. But if it is lots of small areas, then one of the other solutions would have to be settled on. (If you do recreate the area with the pen tool make sure your image is high enough resolution to make it worth the effort {In other words if the resolution is too low, your wasting your time} )