Quant-Iron

A high-performance, hardware-accelerated modular quantum computing library with a focus on physical applications.

Quant-Iron provides tools to represent quantum states, apply standard quantum gates, perform measurements, build quantum circuits, and implement quantum algorithms.

Table of Contents

• Features
• Getting Started
  • Installation
  • Quickstart
• License
• Future Plans

Features

• Quantum State Representation: Create and manipulate predefined or custom quantum states of arbitrary qubit count.

• Standard Operations: Hadamard (H), Pauli (X, Y, Z), CNOT, SWAP, Toffoli, Phase shifts, Rotations, and custom unitary operations.

• Parametric Gates: Support for parametrised gates allowing for dynamic adjustment of gate parameters.

• Hardware Acceleration: Optimised for parallel execution (CPU and GPU) and low memory overhead, with OpenCL-accelerated operations for enhanced performance on compatible hardware. (Requires gpu feature flag).

• Circuit Builder: High-level interface for constructing quantum circuits with a fluent API and the circuit! macro with support for subroutines.

• Measurement: Collapse wavefunction in the measurement basis with single or repeated measurements in the Computational, X, Y, and custom bases.

• Pauli String Algebra:

  • Represent products of Pauli operators with complex coefficients (PauliString).

  • Construct sums of Pauli strings (SumOp) to define Hamiltonians and other observables.

  • Apply Pauli strings and their sums to quantum states.

  • Calculate expectation values of SumOp with respect to a quantum state.

  • Apply exponentials of PauliString instances to states.

• Predefined Quantum Models:

  • Heisenberg Model: Generate Hamiltonians for 1D and 2D anisotropic Heisenberg models using SumOp.
  • Ising Model: Generate Hamiltonians for 1D and 2D Ising models with configurable site-specific or uniform interactions and fields using SumOp.

• Predefined Quantum Algorithms:

  • Quantum Fourier Transform (QFT): Efficiently compute the QFT for a given number of qubits.
  • Inverse Quantum Fourier Transform (IQFT): Efficiently compute the inverse QFT for a given number of qubits.

• OpenQASM 3.0 Support: Convert circuits to OpenQASM 3.0 for interoperability with other quantum computing platforms.

• Extensibility: Easily extensible for custom gates and measurement bases.

• Error Handling: Comprehensive error handling for invalid operations and state manipulations.

• Quality of Life: Implementation of std and arithmetic traits for easy, intuitive usage.

Getting Started

Installation

Add quant-iron to your Cargo.toml:

[dependencies]
quant-iron = "0.1.0"

Or via cargo:

cargo add quant-iron

Quickstart

Create a new quantum state, apply gates, and measure:

fn qubits() {
    // Initialise a 2-qubit |++> state
    let measurement = State::new_plus(2)?
        .h(0)               // Hadamard on qubit 0
        .x(1)               // Pauli-X on qubit 1
        .h_multi(&[0, 1])   // Hadamard on both qubits
        .cnot(0, 1)         // CNOT with control=0, target=1
        .measure_n(MeasurementBasis::Computational, &[0, 1], 100)?; // Measure both qubits 100 times

    println!("Measurement results:\n{:?}", measurement);            // Print the results of the measurement
}

Build a quantum circuit with a QFT subroutine and execute it on a state:

fn circuits() {
  // Build a circuit with 3 qubits
  let circuit = CircuitBuilder::new(3)
    .h_gate(0)                                                  // Add a Hadamard gate on qubit 0
    .cnot_gate(0, 1)                                            // Add a CNOT gate with control=0 and target=1
    .x_gates(vec![1, 2])                                        // Add Pauli-X gates on qubits 1 and 2
    .add_subroutine(Subroutine::qft(vec![1, 2], 3))             // Add a QFT subroutine on qubits 1 and 2 for the 3 qubit system
    .measure_gate(MeasurementBasis::Computational, vec![0, 1])  // Measure qubits 0 and 1
    .build();                                                   // Build the circuit

  let result = circuit.execute(State::new_plus(3)?);        // Execute the circuit on the |++> state
  println!("Circuit result: {:?}", result);                 // Print the result of the circuit execution
}

Build a parametrised circuit and update its parameters:

fn parametric() {
    // Create new parameters
    let angles_1 = Parameter::new([PI / 4.0, PI / 2.0]);            // Theta & Phi

    let angles_2 = Parameter::new([PI / 3.0, PI / 6.0, PI / 12.0]); // Theta, Phi1 & Phi2

    let _circuit = CircuitBuilder::new(3)
        .parametric_ry_phase_gate(0, angles_1.clone())              // Add a parametrised ry_phase gate
        .parametric_ry_phase_gate(2, angles_1.clone())              // Add a parametrised ry_phase gate with shared parameters
        .parametric_matchgate(1, angles_2.clone())                  // Add a parametrised matchgate
        .build_final()
        .expect("Failed to build circuit");

    angles_1.set([PI / 2.0, PI / 3.0]);  // Update parameters
    
    println!("{:?}", angles_2.get());    // Get parameters
}

Use the circuit! macro to build a circuit:

fn circuit_macro() {
    // Use the `circuit!` macro to build a circuit
    let circuit = circuit! {
        qubits: 3,           // Define a circuit with 3 qubits
        h(0),                // Hadamard on qubit 0
        x([1, 2]),           // Pauli-X on qubits 1 and 2
        cnot(0, 1),          // CNOT with target = 0 and control = 1
        crx([1, 2], 0, 1.0), // Controlled RX rotation with targets = 1, 2, control = 0, angle = 1.0
        measurex([0, 1]),    // Measure qubits 0 and 1 in the X basis
        measurez(2)          // Measure qubit 2 in the Z basis
    }.expect("Failed to create circuit");

    println!("{:?}", circuit); // Print the created circuit
}

Define a Hamiltonian and compute its expectation value:

fn hamiltonian() {
  // Define a Hamiltonian for a 2-qubit system
  let hamiltonian = SumOp::new()                                                  // 2 X_0 + Y_1 + 0.5 Z_0 X_1
    .with_term(PauliString::new(2.0).with_op(0, Pauli::X))                        // 2X_0
    .with_term(PauliString::new(1.0).with_op(1, Pauli::Y))                        // Y_1
    .with_term(PauliString::new(0.5).with_op(0, Pauli::Z).with_op(1, Pauli::X));  // 0.5Z_0 X_1

  let state = State::new_plus(2)?;                                // Initialise a |++> state
  let expectation_value = hamiltonian.expectation_value(&state)?; // Compute the expectation value for the given state

  println!("Expectation value: {:?}", expectation_value);         // Print the expectation value for the Hamiltonian
}

Create a Hamiltonian for the 1D Heisenberg model and execute it on a state:

fn heisenberg() {
  // Define a Hamiltonian for the 1D Heisenberg model
  let number_of_spins = 3;
  let coupling_constant_x = 1.0;
  let coupling_constant_y = 2.0;
  let coupling_constant_z = 3.0;
  let field_strength = 0.5;
  let magnetic_field = 0.1;

  let hamiltonian = heisenberg_1d(number_of_spins, coupling_constant_x, 
  coupling_constant_y, coupling_constant_z, field_strength, magnetic_field)?;

  let state = State::new_plus(3)?;                  // Initialise a |+++> state
  let modified_state = hamiltonian.apply(&state)?;  // Apply the Hamiltonian to the state
  println!("Modified state: {:?}", modified_state); // Print the modified state
}

Create a circuit and convert it to OpenQASM 3.0:

use std::f64::consts::PI;

fn qasm() {
    // Create a circuit
    let circuit = CircuitBuilder::new(5)
    .h_gate(0)
    .cx_gates(vec![1, 2], vec![0])
    .p_gates(vec![0,1,2], PI)
    .measure_gate(MeasurementBasis::X, vec![0, 1])
    .swap_gate(3, 4)
    .ctdag_gates(vec![2, 3], vec![0, 3])
    .crz_gates(vec![4], vec![0, 1], PI)
    .measure_gate(MeasurementBasis::Custom([[0.0.into(), 1.0.into()], [1.0.into(), 0.0.into()]]), vec![2, 3, 4])
    .build_final();

    // Convert circuit to OpenQASM 3.0
    println!("{}", circuit.to_qasm(None::<&str>).expect("Could not convert circuit to QASM"));
}

The code examples above demonstrate common use cases of Quant-Iron, and can be run using the cargo run --example {example-name} command.

License

This project is licensed under the MIT License.

Future Plans

• Density Matrix Support: Extend to mixed states and density matrices for more complex quantum systems.
• Circuit Visualisation: Graphical representation of quantum circuits for better understanding and debugging.
• Quantum Arithmetic & Algorithms: Implement common subroutines (e.g. Grover's algorithm, Variational Quantum Eigensolver (VQE)).