Quantum physics you can play in Minecraft.
QAcraft is a Paper plugin that turns three famous quantum protocols into hands-on Minecraft experiments. You build the machines, send the photons and watch what happens.
| Protocol | What it shows |
|---|---|
| BB84 | Two players make a secret key out of photons |
| Grover | Quantum search: find the right chest out of 8 in about 2 steps |
| E91 | Entangled photons react together - and give away any spy |
There is also a decorative particle "atom" and a built-in tutorial that walks you through everything step by step.
- Java 25 or newer - adoptium.net
- A Paper 26.1.2+ server - papermc.io
No Maven install needed - the wrapper downloads it on first run.
Windows: double-click build.bat, or:
mvnw.cmd clean packageLinux / macOS:
./mvnw clean packageYou get the plugin at target/QAcraft.jar.
- Copy
target/QAcraft.jarinto your server'splugins/folder. - Restart the server.
- In game, type
/qacraft help.
The easiest way to start:
/qacraft world build- builds a tutorial hall next to you./qacraft tutorial start- starts the guided tour (or press the Start Tutorial button in the hall lobby).
The tutorial walks you through all three experiments one step at a time. Finish a room and the door to the next one opens.
Every hall and every tour has a number, so several groups can work at the
same time. Others join yours with /qacraft tutorial join <id> and step
out with /qacraft tutorial leave; the tour ends when the last player
leaves.
Everything is under /qacraft (short: /q, /qac).
| Command | What it does |
|---|---|
/qacraft help |
Show help in game |
/qacraft tools <bb84|grover|e91|all> |
Get the tools for a protocol (clears your inventory first) |
/qacraft item <name> |
Get one tool and keep your inventory |
/qacraft clear |
Remove everything the plugin created |
| Command | What it does |
|---|---|
/qacraft sender place |
Place the transmitter |
/qacraft sender fill [filters|photons|both] |
Fill its chest: filters only (default), bits only, or both |
/qacraft sender start |
Send all 27 photons, done in about five seconds |
/qacraft sender stop |
Stop sending |
/qacraft gate place |
Place a measuring gate |
/qacraft gate <id|all> fill |
Fill that gate's chest with 27 random filters |
/qacraft gate <id|all> clear |
Remove that gate, or all of them |
/qacraft cipher |
Encrypt a number with the key - also a button in the [Esc] menu |
/qacraft wp [place|clear] |
Place or clear photon stations |
/qacraft parking |
Place a parking spot |
/qacraft send <rect|diag> <0|1> |
Send one photon by hand |
/qacraft photon <clear|info> |
Remove photons or show their state |
You can run several search grids at once. Each grid shows its number in the middle. Add the number after a command, or leave it out when there is only one grid. Grids cannot overlap - build the next one at least five blocks away. A grid always searches exactly 8 chests.
There are two ways to build one. The Fire Charge marks a ring of 8 slots around you. The Heavy Core ("Custom Setup") lets you put the chests wherever you like: drop the core, build as many chests as you want within 10 blocks, then right-click the core again to lock them in. While you build, the core shows a live count above itself. Click the core again later to reopen the grid and change the chests. A custom grid works with the number of chests you confirmed, so 4 chests are already certain after one step. Both kinds share the same numbering, so the first grid is #1 whichever way you made it.
A slowly turning heavy core marks the middle of every grid. Once the search finds the item, the core shoots a beam at the right chest.
| Command | What it does |
|---|---|
/qacraft grover setup [id] |
Mark 8 spots for a new grid |
/qacraft grover custom |
Drop a heavy core; run it again to confirm the chests around it |
/qacraft grover placechests [id] |
Place the chests |
/qacraft grover fillwool [id] |
Put a different wool in every chest |
/qacraft grover iterate [id] |
Run one Grover step (or throw a Wind Charge) |
/qacraft grover reset [id] |
Start the search over |
/qacraft grover clear [id] |
Remove one grid, or all grids without an id |
/qacraft grover list |
Show the active grids |
The first step only works while you hold the item you are searching for. Then hold the Spyglass (main hand) and the item (offhand) to see the probability bars. Place the reset TNT on the middle block to blow a grid away.
| Command | What it does |
|---|---|
/qacraft e91 source |
Place the photon-pair source |
/qacraft e91 alice / bob |
Mark Alice's and Bob's side |
/qacraft e91 generate |
Send one entangled pair |
/qacraft e91 start / stop |
Send pairs automatically |
/qacraft e91 key |
Show the secret key |
/qacraft e91 bell |
Run the Bell test |
/qacraft e91 eve |
Turn the spy on or off |
/qacraft e91 clear |
Remove everything E91 |
Hold a Compass, Recovery Compass or Clock next to a landed photon to measure it.
| Command | What it does |
|---|---|
/qacraft plasma |
Get the plasma tools (summon and remove the particle atom) |
/qacraft plasma clear |
Remove all plasmas |
/qacraft world build [id] |
Build a tutorial hall |
/qacraft world clear [id] |
Remove a hall (nearest one without an id) |
/qacraft world list |
List the halls in the world |
/qacraft tutorial start [id] |
Start the guided tour in a hall |
/qacraft tutorial join <id> |
Join a tour somebody else started |
/qacraft tutorial leave |
Leave your tour; the last one out ends it |
/qacraft tutorial list |
List the running tours |
| Item | What it is | Protocol |
|---|---|---|
| Compass | Rectilinear filter (+) | BB84 / E91 |
| Recovery Compass | Diagonal filter (×) | BB84 / E91 |
| Clock | Circular filter (○) | E91 |
| Snowball | Photon source | BB84 |
| Carrot on a Stick | Photon station | BB84 |
| Warped Fungus on a Stick | Parking spot | BB84 |
| Nether Star | Transmitter | BB84 |
| Eye of Ender | Measuring gate | BB84 |
| Fire Charge | New search grid (ring of 8) | Grover |
| Heavy Core | New search grid, chests where you want | Grover |
| Conduit | Place the chests | Grover |
| Wind Charge | One Grover step | Grover |
| Spyglass | Show probabilities | Grover |
| TNT | Blow a grid away | Grover |
| Amethyst Shard | Photon-pair source | E91 |
| Diamond Axe | Alice's landing pad | E91 |
| Gold Axe | Bob's landing pad | E91 |
| Heart of the Sea / Echo Shard | Summon / remove plasma | Lobby |
| Brush | Eraser for plugin things | BB84 / E91 |
Filter colours match the items: rectilinear red, diagonal cyan, circular yellow.
Tools build their apparatus where you are aiming - point at a block, right-click, and it lands centred on that block.
The BB84 transmitter only starts once the whole setup is there: the transmitter, its filled double chest and at least one Quantum Cable. Photon stations show their route: a dotted line joins them with a green dot running from the lower number to the higher one. Photons fly down the middle of that line, and after the last station they fly on to their own parking spot - or stop in the middle of the last station if they have none.
Command blocks run any command as it stands - the block acts for the
nearest player within 48 blocks, the same way @p works.
Everything the hall is built from is indestructible; blocks you place yourself can always be mined away again.
Everything survives a server restart - photons, gates, grids, the hall.
Use /qacraft clear when you want a clean slate.
The full step-by-step guide with pictures is
docs/QAcraft-Guide.docx.
Made by NVIAS for the Czech-Bavarian Quantum Academy project (Interreg Bayern-Tschechien, BYCZ10-263).