# Single-Slit Diffraction Demo
## The Prompt
```
Simulate single-slit diffraction: create a barrier with one narrow slit,
send a Gaussian wavepacket through it, and show me the diffraction pattern.
Use a 256x256 grid for a 2D simulation.
```
## MCP Tool Sequence
### Step 1: Create the Barrier Potential
```tool
mcp__quantum-mcp__create_custom_potential
grid_size: [256, 256]
function: "1000 * ((np.abs(x - 128) < 3) & (np.abs(y - 128) > 8))"
```
This creates a barrier at x=128 with a single slit of width 16 units centered at y=128.
**Response:**
```json
{
"potential_id": "potential://abc123",
"shape": [256, 256]
}
```
### Step 2: Create the Incoming Wavepacket
```tool
mcp__quantum-mcp__create_gaussian_wavepacket
grid_size: [256, 256]
position: [50, 128]
momentum: [2.0, 0]
width: 15
```
A Gaussian wavepacket starting on the left, moving right toward the slit.
**Response:**
```json
{
"wavefunction": [[...], [...], ...]
}
```
### Step 3: Solve the Schrödinger Equation
```tool
mcp__quantum-mcp__solve_schrodinger_2d
potential: "potential://abc123"
initial_state: <wavefunction from step 2>
time_steps: 500
dt: 0.02
```
**Response:**
```json
{
"simulation_id": "simulation://xyz789",
"status": "completed",
"frames": 50
}
```
### Step 4: Visualize the Potential
```tool
mcp__quantum-mcp__visualize_potential
potential_id: "potential://abc123"
output_path: "/tmp/single_slit_potential.png"
```
### Step 5: Render the Animation
```tool
mcp__quantum-mcp__render_video
simulation_id: "simulation://xyz789"
output_path: "/tmp/single_slit_diffraction.mp4"
fps: 30
```
## Expected Results
### The Barrier Potential
A vertical barrier with a single narrow opening. High potential (1000) blocks the wave; zero potential at the slit allows passage.
### The Diffraction Pattern
After passing through the slit, the wave spreads out in the characteristic single-slit pattern:
- Central bright maximum directly behind the slit
- Decreasing intensity side lobes
- Dark minima where destructive interference occurs
### The Physics
The narrow slit localizes the particle's position (Δy small), which by the uncertainty principle increases momentum spread (Δpy large), causing the wave to fan out.
## Variations
### Narrower Slit
```
Make the slit half as wide and show how the diffraction pattern changes.
```
Result: Wider angular spread (more diffraction)
### Higher Momentum
```
Double the incoming momentum and compare the patterns.
```
Result: Narrower diffraction pattern (shorter effective wavelength)
