Quantenquartett (German for "quantum quartet") is a card game of unknown origins adapted from Happy Families or Authors ("Quartett" in German) with one major difference: Quantenquartett is played without cards. This game takes at least 3 players, though more than 4 players is recommended for the adventurous only.
From the wikipedia article of Happy Families:
Happy Families is a card game, usually with a specially made set of picture cards featuring illustrations of fictional families of four. The object of the game is to collect complete families. The player whose turn it is asks another player for a specific card from the same family as a card that the player already has. If the asked player has the card, he gives it to the requester and the requester can then ask any player for another card. If the asked player does not have the card, it becomes his turn and he asks another player for a specific card. Play continues in this way until no families are separated among different players. The player with the most cards wins.
In Quantenquartett, every player begins with four undefined cards, and the first player to assemble a family is usually considered the winner. Cards and hands are defined through play. Otherwise, rules from Happy Families apply.
For example, let the players be named Alice, Bob, and Carol, and they each have four undefined cards. Then Alice (or Bob, or Carol) can start the game by asking one of her fellow players a question, for example:
Alice: "Bob, do you have the apple in the family of fruits?" Then we know that Alice must have at least one card in the family of fruits, as she must follow the rules.
If Bob answers yes, then Bob must give the apple card to Alice, such that Bob will only have three undefined cards, and Alice will have 3 undefined cards, one card in the family of fruits, and the apple. Bob will then pose the next question.
If Bob answers no, then we know that either Alice or Charlie must have the apple, as the card has been introduced correctly and must thus exist in the game. Then Bob will have 4 undefined cards, Alice will have 3 undefined and one in the family of fruits (which can be the apple). Alice will continue asking questions.
The game will end under two conditions: a) A player assembles a full family -> they win. b) A player creates a paradox (i.e. break one of the rules) -> they lose.