Quantum Quartets will break your mind (in a good way)

What if I told you the most fun I ever had playing a card game was with no cards at all?

Quartets is a card game (with real cards) about collecting four of a family of cards that is widely popular in Germany (and potentially other places).

Quantum Quartets is played solely within the minds of the players and cards are created in a quantum-mechanical way (of sorts, I'm not a physicist, please don't sue me).

The aim of the game is to accumulate one full family in your own hand, but to get there you'll have to work with your team. Whoever is the first to have a complete family of four in their hand wins. If you make a mistake, everyone loses.

The structure of the deck

It might sound strange to talk about a deck that doesn't exist yet, but it still has a structure.

Each card belongs to a family (or category if you prefer) and has a name, with each family consisting of four cards with unique names. For each player who participates in a round of Quantum Quartets one potential family is added to the game.

A good group to start playing Quantum Quartets with consists of three or four people, but for our purposes we'll assume four people playing. This puts our deck of cards at a manageable size of 16 cards.

How to start playing

Each player starts with four blank cards in their hand. Keep in mind that these don't have a physical representation and only exist in the minds of the people playing.

But what cards are they?

Just as with regular Quartets, the game starts with one person asking another if they have a specific card from a specific family. The key to Quantum Quartets is that only through asking questions, cards and families are created. Which families and which cards is up to the players, who usually choose not to reuse cards from one round to another.

Ingo, asking Maria: Do you have PostgreSQL from the family of Databases?

Maria: Yes. Maria gives Ingo the PostgreSQL card.

A few things have happened as a result of this interaction. In this round, one of the four families is now called Databases and one card called PostgreSQL is now in Ingo's possession.

Why did Maria say yes, if all she had was blank cards?

One of the core concepts of Quantum Quartets is that anything that could be possible can become reality if you choose to.

Therefore, it was her free choice. At this point she could have also said no, which would have still brought the family of Databases and the card PostgreSQL into existence, but in that scenario PostgreSQL lies in a sort of quantum state in the hands of both other players, until one of them is asked if they have it and they either choose to say yes (handing it over to whomever asked them for it) or by logical consequence (if they are the only person who can have the card).

Leo, asking Ingo: Do you have xkcd from the family of web comics?

Ingo: No.

Ingo could have said yes and hand Leo the xkcd card, but since he said no the card is now in unknown hands but still exists: Either Maria or the fourth player Tobias must have it. Who exactly is not known yet, but we've learned anything that could be possible can become reality in Quantum Quartets!

Maria, asking Tobias: Do you have xkcd from the family of web comics?

Tobias: No.

If you're hearing the sound of a Jenga tower falling in your head then you're not mistaken: Tobias just lost everyone this round by committing a logical error! 🤯

What happened?

Previously, Leo asked Ingo if he had xkcd from the family of web comics, but Ingo denied having it, which was legal since both Maria or Tobias could still be in possession of the card.

Now that Maria asked Tobias for xkcd, implying that she also doesn't have it, the card materialized in Tobias' hands: He was the only one left who could have it, so he needed to say yes when Maria asked him for it.

Go play!

If you commit the rules of Quantum Quartets to your head you always have everything you need on hand to play a round, no (real) cards needed ¹!

Rules

• Edit to clarify: This game is played without physical cards or other physical representations of cards.
• Each player starts with four blank cards in their hands.
• For each player, one family can be created, but not necessarily by each player themselves.
• A family consists of exactly four individual cards.
• The game ends in a win for the player who first collects all four cards of one family.
• Asking someone for a card implies you don't have it yourself.
• If you have a card or would need to have it due to logical constraints, you must answer yes if asked for it.
• If you could have a card that either you or another player could potentially have, then you may choose whether to answer yes or no.
• Whenever you choose to or have to answer yes to a card inquiry, you must hand it over to the player who asked you for the card.
• If you can't have a card due to logical constraints, you must answer no.
• Turns to ask a question are passed on clockwise.
• Breaking any of these rules by asking or answering incorrectly is a logical error.
• The game ends in a loss for everyone if someone commits a logical error.

What you can do after playing Quantum Quartets

• Write a comment or blog post about what could be an optimal strategy to play this game (or just your favourite ones).
• Write about other games that can be played entirely within the minds of the players.
• Spread the word about Quantum Quartets by playing it with your friends or sharing this post (or even your own if you decided to do the above).