prism-q 0.28.0

PRISM-Q: Performance Rust Interoperable Simulator for Quantum
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# Your First Circuit

There are two ways to build a circuit: the fluent `CircuitBuilder` API, or by parsing
OpenQASM text.

## With the builder

`CircuitBuilder` chains gate calls and runs the result. This builds a Bell pair, the
two-qubit entangled state `(|00⟩ + |11⟩) / √2`:

```rust
use prism_q::CircuitBuilder;

let result = CircuitBuilder::new(2)
    .h(0)
    .cx(0, 1)
    .run(42)                       // seed = 42
    .expect("simulation failed");

let probs = result.probabilities.expect("no probabilities");
for i in 0..probs.len() {
    let p = probs.get(i);
    if p > 1e-10 {
        println!("|{i:02b}> = {p:.4}");
    }
}
// |00> = 0.5000
// |11> = 0.5000
```

A larger structurally similar circuit, the 5-qubit GHZ state, renders like this (diagram
generated by PRISM-Q's own SVG renderer):

![GHZ state preparation circuit](../diagrams/ghz_5.svg)

## From OpenQASM

The same Bell pair, written in OpenQASM 3.0 and parsed:

```rust
use prism_q::circuit::openqasm;
use prism_q::simulate;

let qasm = r#"
    OPENQASM 3.0;
    include "stdgates.inc";
    qubit[2] q;
    h q[0];
    cx q[0], q[1];
"#;

let circuit = openqasm::parse(qasm).expect("failed to parse QASM");
let result = simulate(&circuit).seed(42).run().expect("simulation failed");
```

`run_qasm(qasm, seed)` is a shortcut that parses and simulates in one call. See the
[OpenQASM Support guide](../guides/openqasm.md) for the supported subset.

```admonish note title="Qubit ordering"
`q[0]` is the least significant bit, so `x q[0]` produces state index 1, not 2. Bitstrings
print most-significant qubit first.
```

Next: sample measurement outcomes in [Shots and Sampling](./shots.md).