I can not summon xp_orb.

Try using
/summon minecraft:xp_orb
instead of just
/summon xp_orb
You can also use the /xp command instead.
For example:
/xp 10L @s
gives 10 levels to the player, and
/xp 1000 @r
gives 1000 experience orbs to a random player

Thank you for your report!
We're tracking this issue in MCPE-130835, so this ticket is being resolved and linked as a duplicate.

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