The Premier League club revealed last week that they were monitoring the availability of the 23-year-old and he has now become Stoke's fifth close-season signing, much to the delight of manager Mark Hughes, who spent one season as a player at Camp Nou.
"Anyone who knows European football will be aware of him as a player and the fact that he sees his future at Stoke City is really exciting and an endorsement of the club itself," said Hughes.
"He's desperate to prove himself in the Premier League and we're pleased to be able to offer him that platform.
"The time he spends with the squad in Germany [on the club's pre-season tour] will help him settle in and will give myself and the coaches the chance to take a good look at him."
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