I have very strong desire to use superscript as the index of the variable.

However, it looks like that the Mathematica automatically recognize the superscript as the power and I got message that my variable with superscript is 'protected'.

Could you help me to make the superscript used as the index of the variable instead of power?

UPDATE (16-June-2015):

This question is being reopened and a bounty is being awarded on this. Previous answers are very good, however the bounty is to be awarded on an answer which solve this specific problem: 


  How to change the behaviour of Ctrl+^ keybinding so that it produces Superscript instead of Power.



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