Accurate ground-state calculations on noisy quantum computers are significantly constrained by restricted Ansatz expressivity and unavoidable hardware errors. We introduce a hybrid quantum-classical framework that simultaneously addresses these challenges. Our method systematically purifies noisy two-electron reduced density matrices from quantum devices by enforcing $N$-representability conditions through efficient semidefinite programming, guided by a norm-based distance constraint to the experimental data. To implement this constraint, we develop a hardware-efficient calibration protocol based on Clifford circuits. We demonstrate near full configuration-interaction accuracy for ground-state energies of ${\mathrm{H}}_2$, $\mathrm{Li}\mathrm{H}$, and ${\mathrm{H}}_4$, and compute precise scattering intensities for ${\mathrm{C}}_6{\mathrm{H}}_8$ on noisy hardware. This approach surpasses conventional methods by simultaneously overcoming both Ansatz limitations and hardware noise, providing a framework for quantum advantage and offering an alternative for reliable simulations of complex molecular systems on noisy devices.

Close

PrevNext

View figure in article

• Chemical Physics & Physical Chemistry
• Electronic structure of atoms & molecules
• Molecular dissociation
• Noise
• Quantum algorithms for chemical calculations
• Quantum computation
• Molecules
• Quantum many-body systems