QAcraft

Quantum physics, playable in Minecraft. QAcraft is an educational Paper plugin that turns three landmark quantum-information protocols into hands-on, visual experiments you can run inside a Minecraft world — built for lectures and workshops at the Czech–Bavarian Quantum Academy.

Protocol	What you demonstrate
BB84	Quantum key distribution — encode photons in random bases, measure, sift a shared key
Grover	Quantum search — find the marked item in √N steps with amplitude amplification
E91	Entanglement-based QKD — Bell pairs, correlated measurements, eavesdropper detection

Plus a lobby plasma "atom" particle effect and a built-in guided tutorial for workshops.

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Requirements

• Java 21 or newer — Adoptium / Temurin
• Paper 1.21.4+ server (papermc.io)

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Build

No Maven installation required — the wrapper downloads it automatically on first run.

Windows: double-click build.bat, or:

mvnw.cmd clean package

Linux / macOS:

./mvnw clean package

The compiled plugin lands at target/QAcraft.jar.

Install

1. Copy target/QAcraft.jar into your server's plugins/ folder.
2. Start (or restart) the server.
3. In game, run /qacraft help.

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Try it on your own

The quickest way to meet the plugin — build the tutorial hall and take the guided walkthrough:

1. /qacraft world build — builds a decorated tutorial hall (Lobby → BB84 → Grover → E91) next to you.
2. /qacraft tutorial start — starts the interactive, gated walkthrough inside it (or press the Start Tutorial button in the hall lobby).

The tutorial teleports you into the hall and guides you step by step: each protocol room must be completed hands-on before its door opens. Wall panels, floating "X here" markers, live "Missing: …" chest hints, and in-room "give tools" buttons walk a newcomer through every experiment.

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Commands

All commands are under /qacraft (aliases: /q, /qac).

General

Command	Description
/qacraft help	Show the in-game help
/qacraft tools <bb84|grover|e91|all>	Give a protocol's tools (clears your inventory first)
/qacraft item <name>	Give one named tool without clearing your inventory (tab-complete for names)
/qacraft clear	Remove every QAcraft entity in all worlds

BB84 — Quantum Key Distribution

Command	Description
/qacraft sender place	Place the transmitter (snaps to block centre; outlines mark the double chest)
/qacraft sender fill	Fill the double chest with 27 random basis filters
/qacraft sender start	Transmit — one photon per second (27 total)
/qacraft sender stop	Stop transmitting
/qacraft gate place	Place a measurement gate (outline marks its filter chest)
/qacraft gate clear	Remove all gates
/qacraft wp [place|clear]	Route waypoints for photons
/qacraft parking	Place a parking spot
/qacraft send <rect|diag> <0|1>	Manually send one photon with a given basis and bit
/qacraft photon <clear|info>	Clear photons / print their hidden state

Grover's Search

Multiple independent grids can run at once — each is identified by an id shown on a big number floating in its centre. Give the id after each command (omit it when only one grid exists).

Command	Description
/qacraft grover setup [id]	Mark 8 positions in a ring (new grid; auto-assigns the lowest free id)
/qacraft grover placechests [id]	Auto-place chests on the marked positions
/qacraft grover fillwool [id]	Put a random wool colour in each chest
/qacraft grover iterate [id]	Run one Grover iteration (or throw a Wind Charge — iterates the nearest grid)
/qacraft grover reset [id]	Reset to equal superposition
/qacraft grover clear [id]	Remove one grid; without an id, remove all
/qacraft grover list	List the active grids and their iteration counts

The first iteration runs only while you hold the item you are searching for — it becomes the grid's target. Hold the Spyglass in your main hand and the target in the offhand to see the probability columns after the first iteration. Searching for a new item restarts that grid. Drop the Grover Reset (TNT) on a grid's centre block to deactivate it.

E91 — Entanglement Protocol

Command	Description
/qacraft e91 source	Place the entangled-pair (EPR) source
/qacraft e91 alice / bob	Set Alice's / Bob's zone marker
/qacraft e91 generate	Emit one entangled pair
/qacraft e91 start / stop	Auto-generate pairs
/qacraft e91 key	Show the sifted key (same-basis measurements)
/qacraft e91 bell	Show Bell / CHSH correlations
/qacraft e91 eve	Toggle the eavesdropper simulation
/qacraft e91 clear	Remove all E91 entities

Hold a Compass, Recovery Compass, or Clock near an arrived photon to measure it in the rectilinear, diagonal, or circular basis.

Lobby & Workshop

Command	Description
/qacraft plasma	Get the Plasma tools — right-click Heart of the Sea to summon a particle "atom", Echo Shard to remove the nearest
/qacraft plasma clear	Remove all plasmas
/qacraft world build	Build a decorated tutorial hall (Lobby → BB84 → Grover → E91) next to you
/qacraft world clear	Remove the hall and restore the ground
/qacraft tutorial start	Start the interactive, gated walkthrough inside the built hall
/qacraft tutorial stop	End the walkthrough (clears placed apparatus and chests)

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Tools

Item	Tool	Protocol
Compass	Rectilinear filter (+)	BB84 / E91
Recovery Compass	Diagonal filter (×)	BB84 / E91
Clock	Circular filter (○)	E91
Snowball	Quantum source	BB84
Carrot on a Stick	Quantum cable (waypoint)	BB84
Warped Fungus on a Stick	Parking spot	BB84
Nether Star	Quantum sender	BB84
Eye of Ender	Quantum gate	BB84
Fire Charge	Grover setup (new grid)	Grover
Conduit	Place chests on the nearest grid	Grover
Wind Charge	Grover operator (iterate)	Grover
Spyglass	Quantum observer	Grover
TNT	Grover reset (drop on grid centre)	Grover
Amethyst Shard	EPR source	E91
Diamond Axe	Alice landing pad (R) / zone (L)	E91
Gold Axe	Bob landing pad (R) / zone (L)	E91
Heart of the Sea / Echo Shard	Plasma summon / remove	Lobby
Brush	Quantum eraser	all

Filter colours mirror the compasses: Rectilinear red, Diagonal cyan, Circular yellow.

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Persistence

QAcraft entities (photons, gates, pads, plasmas, tutorial signs) and protocol runtime state survive server restarts — they are saved with the world and to plugins/QAcraft/state.yml. Use /qacraft clear (or the per-protocol clear subcommands) to remove them deliberately.

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Documentation

The step-by-step user guide is docs/QAcraft-Guide.docx — chapter by chapter: tools and items with in-game icons, every command, and each protocol explained.

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Project

Czech–Bavarian Quantum Academy · Interreg Bayern–Tschechien · BYCZ10-263 Developed by NVIAS.