The Alcatraz coup is an illegal method of learning about the opponents' cards in contract bridge.
It is not a true coup, and the phrase itself is a reference to its supposed provenance: the defunct Alcatraz penitentiary.
The "coup" consists of a deliberate revoke by declarer, causing the next player to reveal whether he holds the key card whose location is sought.
It also states that "A player of the offending side may not choose from among logical alternative actions one that could demonstrably have been suggested over another by the unauthorized information."
In other words, even if the coup is executed inadvertently, the declarer may not take advantage of knowing the position of the queen; if he does so, the tournament director may adjust the result accordingly.