QuantRS2-Circuit: Quantum Circuit Construction

QuantRS2-Circuit is part of the QuantRS2 quantum computing framework, providing a flexible API for building and manipulating quantum circuits.

Features

• Fluent Circuit Builder API: Create quantum circuits with an intuitive, chainable interface
• Type-Safe Construction: Compile-time checking of qubit counts and operations
• Comprehensive Gate Support: All standard gates plus controlled variants
• DSL Macros: Convenient macros for circuit creation and manipulation
• Simulator Integration: Seamless connection to various simulator backends

Usage

Creating a Bell State Circuit

use quantrs2_circuit::builder::Circuit;
use quantrs2_core::prelude::*;

fn main() -> QuantRS2Result<()> {
    // Create a circuit with 2 qubits
    let mut circuit = Circuit::<2>::new();
    
    // Build the Bell state circuit
    circuit.h(0)?
           .cnot(0, 1)?;
           
    // The circuit is now ready to run on a simulator
    Ok(())
}

Using Circuit Macros

use quantrs2_circuit::{circuit, qubits};
use quantrs2_core::prelude::*;

fn main() -> QuantRS2Result<()> {
    // Create a circuit with 4 qubits
    let mut circuit = circuit!(4);
    
    // Add gates using the builder API
    circuit.h(0)?
           .cnot(0, 1)?
           .h(2)?
           .cnot(2, 3)?;
           
    // Define a set of qubits to operate on
    let qs = qubits![0, 1];
    
    // Operations can be applied to qubit sets
    // (this feature depends on implementation details)
    
    Ok(())
}

Module Structure

• builder.rs: Main circuit builder implementation
• lib.rs: Module exports and macro definitions

API Overview

Core Types

• Circuit<N>: Quantum circuit with const generic for qubit count
• Simulator: Trait for backends that can run quantum circuits

Macros

• circuit!: Creates a new circuit with the specified number of qubits
• qubits!: Creates a set of qubits for operations
• quantum!: DSL for quantum circuit construction (in development)

Implementation Notes

• The circuit builder uses a fluent API for method chaining
• Gate operations are type-checked at compile time where possible
• The implementation supports custom gates through the GateOp trait
• Circuit operations return QuantRS2Result for error handling

Future Plans

See TODO.md for planned improvements and features.

Integration with Other QuantRS2 Modules

This module is designed to work seamlessly with:

• quantrs2-core: Uses core types and gates for circuit construction
• quantrs2-sim: Circuits can be executed on simulators
• quantrs2-device: Circuits can be transpiled and run on real hardware

License

This project is licensed under either:

• Apache License, Version 2.0
• MIT License

at your option.