Make SKSpriteNode edges smooth after rotation

I create an SKSpriteNode like this:

var shape:SKSpriteNode = SKSpriteNode(color: UIColor.redColor(), size: CGSizeMake(CGFloat(sizeOfShape), CGFloat(sizeOfShape)))

      

        
        
        
      

    

How can I achieve that the SKSpriteNode still has smooth edges after I rotated it.

It currently looks like this:

As you can see, the edges are jagged.