Changelog

The format is based on Keep a Changelog, and uses Semantic Versioning.

[1.3.0] - 2026-06-24

Added

  • Classical Chemistry Calculators

    We added several new classical chemistry reference calculators including:

    • Second-order Møller-Plesset (MP2) ground-state problem calculator and reaction path problems calculator.

    • Coupled cluster (CCSD and CCSD(T)) ground-state problem calculator and reaction path problems calculator.

    • TRIM-CI (Truncated Restricted-active-space Interaction with Many-body perturbation) configuration interaction calculator.

    We also added the coupled cluster singles and doubles (CCSD) as a new molecular orbital calculator.

  • Tensor Network Simulation

    We added a new tensor network simulation module with support for both CPU and GPU backends.

  • GPU Acceleration

    We have added GPU-acceleration to the orbital optimization Hessian (supported on Linux and MLX support on macOS) We have also added the CuQuantum state-vector estimator for GPU-accelerated exact simulation.

  • Optional Extras for Hardware Backends

    Hardware backend dependencies (IBM, IQM, OQC, CUDA) have been restructured as pip optional extras. This means a bare pip install qrunch no longer pulls in heavy, backend-specific dependencies you may not need. Install only the extras required for your target hardware, e.g. pip install qrunch[iqm] to get the IQM backend working. Multiple extras can be combined: pip install qrunch[iqm, oqc]. To restore the previous behaviour where all backend dependencies are included, use pip install qrunch[all].

  • Shadow Grouper

    We added a Shadow grouper that creates groups by sampling the most important Pauli strings for the observable first.

  • Better shot utilisation

    We changed the definition of shots and added shot distributors with the new .with_total_estimator_shots(shots=1_000_000) method. The new method sets the total number of shots and distributes them across measurement groups, ensuring better use of the shot budget on hardware. The existing .with_estimator_shots(shots=1000) continues to work as before, setting the number of shots per call to the quantum computer or simulator. But deprecated in the next release.

  • Performance Improvements

    • Several general performance improvements.

    • Performance improvements for OO-FAST-VQE and OO-BEAST-PT2 VQE workflows.

[1.2.0] - 2026-05-22

Added

  • Rigetti Cepheus 108Q support via Amazon Braket.

  • Auxiliary energy contributions (DFT mean-field energies) for projective embedding problems.

  • Active electrons correlation energy property added on GroundStateProblemCalculatorResult

  • Verification that hardware backends function correctly on creation of a backend sampler or estimator.

  • Data persister support for the Configuration Interaction calculator.

  • Improved default for RI/Auxiliary basis sets.

  • VQE warm start utilities for starting VQE calculations from a previous result, a custom circuit, or a parameterized circuit.

Changed

  • Upgraded Qrunch to Python 3.12.

Fixed

  • Fixed measurement result bit ordering for IQM backends.

  • Fixed memory leak in RI integral evaluation.

  • Fixed support for Amazon Braket Hybrid Jobs.

[1.1.0] - 2026-03-03

Added

  • BEAST-PT2 (Second-Order Correction for BEAST-VQE)

    BEAST-VQE can now be augmented with a second-order perturbative correction to improve accuracy beyond the paired-electron approximation. The correction supports pair-breaking effects, single excitations, or both, and can be enabled directly in the calculator configuration.

  • Noisy Memory Restricted Simulator

    A new memory-restricted simulator can emulate physical quantum hardware, including user configured device data. It combines the standard memory restricted simulator with Monte Carlo sampling, to emulate hardware-like behavior based on calibration data.

  • GPU Acceleration

    We introduced a new GPU acceleration module with initial support for accelerated orbital rotations, providing improved performance for selected workflows.

  • Hardware Backend Improvements

    • Support for IBM NightHawk architecture devices (e.g., Miami).

    • Optional instance selection for IBM Quantum Platform backends.

    • Improved robustness of IQM backends when handling missing qubits or calibration data.

  • Performance Improvements

    • Faster mapping from second-quantized Hamiltonians to Pauli operators.

    • Performance improvements for FAST-VQE and BEAST-VQE workflows.

    • Reduced logging overhead in the memory-restricted simulator.

Deprecated

  • Tensor Hypercontraction integrals have been deprecated as it never worked to our satisfaction and it will be removed in a future release.

Fixed

  • Fixed a performance issue in even-handed projective-embedding calculations.