Struct MultiBodyQuantumSolver 

pub struct MultiBodyQuantumSolver {
    pub n_particles: usize,
    pub local_dim: usize,
    pub tolerance: f64,
    pub max_sweeps: usize,
}

CPU exact-diagonalization solver for small multi-body quantum Hamiltonians.

Diagonalizes the full Hamiltonian matrix exactly via Jacobi iteration for Hermitian matrices with dimension ≤ 2^20 (typically ≤ 20 qubits). For very small systems (dim ≤ 512) the algorithm converges quickly; for larger ones it is still correct but will be slow — use GPUMultiBodyQuantumSolver for production large-system calculations.

Fields

n_particles: usize

Number of particles / sites in the many-body Hilbert space.

local_dim: usize

Local Hilbert-space dimension per site (e.g. 2 for spin-1/2).

tolerance: f64

Convergence tolerance for the Jacobi sweeps.

max_sweeps: usize

Maximum number of Jacobi sweeps.

Implementations

impl MultiBodyQuantumSolver

pub fn new(n_particles: usize, local_dim: usize) -> Self

Create a new CPU multi-body quantum solver.

Arguments

• n_particles – number of particles / sites.
• local_dim – local Hilbert-space dimension per site (2 for qubits).

pub fn hilbert_dim(&self) -> usize

Total Hilbert-space dimension: local_dim^n_particles.

pub fn diagonalize( &self, hamiltonian: &Array2<Complex64>, ) -> Result<MultiBodyEigenResult>

Diagonalize the given Hermitian Hamiltonian and return all eigenvalues and eigenvectors.

The input must be a square Hermitian matrix whose dimension equals self.hilbert_dim().

pub fn find_ground_states( &self, hamiltonian: &Array2<Complex64>, k: usize, ) -> Result<MultiBodyEigenResult>

Find the k lowest-energy eigenpairs using the Lanczos algorithm.

This is more efficient than full diagonalization for large matrices when only a few eigenvalues are needed.

pub fn build_heisenberg_chain( &self, j_coupling: f64, ) -> Result<Array2<Complex64>>

Build a nearest-neighbor Heisenberg XXX Hamiltonian on a 1D chain with periodic boundary conditions:

H = J Σ_i (S^x_i S^x_{i+1} + S^y_i S^y_{i+1} + S^z_i S^z_{i+1})

This is a convenience constructor for testing and benchmarking. Only works for spin-1/2 (local_dim == 2).