OpenVQE/MyQLM-Fermion | OpenVQE

Release second version of OpenVQE package

Sat, 08 Feb 2025 00:00:00 +0000

Announcing the Release of OpenVQE v2.0!

We are excited to announce the release of the second version of OpenVQE, a major update that brings significant improvements and new features to our quantum variational eigensolver package.

What’s New in OpenVQE OpenVQE v2.0?

Following the success of the first version, OpenVQE v2.0 introduces:

✅ Enhanced Quantum Algorithms – Optimized for better performance in quantum computing simulations.
✅ Expanded Quantum Chemistry Support – New integrations for advanced shortcut amongst the folders
✅ Better Usability & Documentation – Making it easier for researchers and developers to use OpenVQE effectively.

Our Partners & Contributors

We are proud to collaborate with Atos, Sciences Sorbonne Université, TotalEnergies in the first version of OpenVQE. And in this second version with more than 35 contributors around the world that make the second version become more advanced and better

Get Involved!

We invite the community to explore OpenVQE v2.0 and contribute to its ongoing development. Check out the latest version on and try out the new features.

🚀 Let’s push the boundaries of quantum computing together!

The Journal of Physical Chemistry A, 2023, Vol 127/Issue 15, 3543–3550

Fri, 19 Jan 2024 00:00:00 +0000

The reasearch paper “Extension of the Trotterized Unitary Coupled Cluster to Triple Excitations” is now available on The Journal of Physical Chemistry! This release grants some following highlights include:

Highlights include:

The research paper addresses the need to extend the Trotterized Unitary Coupled Cluster Single and Double (UCCSD) ansatz to include true Triple T excitations in order to recover missing correlation effects for molecular simulations on quantum computers
The limitations of UCCSD for larger molecules are discussed, and the addition of (true) Triple T excitations to the UCCSD approach is proposed to improve accuracy.
The paper introduces the Trotterized UCCSDT approach and analyzes the behavior of triple excitations on a set of molecules compared to the initial UCCSD.
The computational methodology used for the theoretical experiments and the results obtained from testing several molecules using UCCSDT-VQE and sym-UCCSDT-VQE methods are presented.
. The significance of incorporating symmetries, such as spin and point group symmetries, to reduce the number of circuit excitations in the UCCSDT ansatz and accelerate the optimization process for tackling larger molecules is emphasized.
The paper provides insights into the UCCSD and Trotterized UCCSD ansatz, acknowledging their successes and limitations in representing wavefunctions for molecular simulations.
The significance of incorporating symmetries, such as spin and point group symmetries, to reduce the number of circuit excitations in the UCCSDT ansatz and accelerate the optimization process for tackling larger molecules is emphasized. Thank you to everyone who contributed to this release!
Extensive numerical tests on molecules such as LiH, BeH2, and H2O using the UCCSDT-VQE and sym-UCCSDT-VQE methods are presented, demonstrating the superiority of the sym-UCCSDT approach in terms of accuracy, particularly in recovering correlation energy missed by the sym-UCCSD ansatz.
The paper highlights the need for further analysis to understand the limitations of the sym-UCCSDT approach at larger bond lengths and suggests potential improvements by adding higher-order excitations, stressing the potential of the Trotterized UCCSDT approach to achieve competitive results with the gold-standard CCSD(T) classical methods

Theoretical Framework and Quantum Computing

The paper describes the theoretical formalism of the Unitary Coupled Cluster (UCC) method for electronic structure calculations, including detailed formalism of triple excitations in its simplified form after applying both spin and orbital symmetries. It highlights the challenges and opportunities associated with the use of quantum computers for solving problems in quantum chemistry, especially in simulating the full configuration interaction wavefunction of many-electron molecular systems. The Variational Quantum Eigensolver (VQE) is discussed as a promising algorithm for practical implementation on Noisy Intermediate Scaled Quantum (NISQ) devices. The paper also provides insights into the UCCSD and Trotterized UCCSD ansatz, acknowledging their successes and limitations in representing wavefunctions for molecular simulations.

Incorporating Symmetries for Computational Efficiency

The authors emphasize the significance of incorporating symmetries, such as spin and point group symmetries, to reduce the number of circuit excitations in the UCCSDT ansatz and accelerate the optimization process for tackling larger molecules. They discuss the reduction in the number of optimization parameters due to the incorporation of symmetry constraints and the use of the Trotterization approach for breaking up the exponential of a sum into a product of individual exponentials

Numerical Tests and Comparative Analysis

The research paper extensively presents the authors’ numerical tests on molecules such as LiH, BeH2, and H2O using the UCCSDT-VQE and sym-UCCSDT-VQE methods. It discusses the reductions in the number of optimization parameters for different molecules and the results obtained, showing that the sym-UCCSDT method improves the overall accuracy by at least two orders of magnitudes with respect to standard UCCSD. The authors compare the performance of the sym-UCCSDT method with classical methods such as CCSD, CCSD(T), and CCSDT-full and demonstrate the superiority of the sym-UCCSDT approach in terms of accuracy, particularly in recovering correlation energy missed by the sym-UCCSD ansatz

Limitations and Future Directions

Furthermore, the paper highlights the need for further analysis to understand the limitations of the sym-UCCSDT approach at larger bond lengths and suggests potential improvements by adding higher-order excitations. It also discusses the implications of the correlation effects on the accuracy of the sym-UCCSDT method and provides a thorough analysis of the errors and energy differences with reference to the FCI energies. The authors stress the potential of the Trotterized UCCSDT approach to achieve competitive results with the gold-standard CCSD(T) classical methods, delineating its significance for the quantum chemistry community

WIREs Computational Molecular ScienceVolume 13, Issue 5 e1664

Wed, 15 Mar 2023 00:00:00 +0000

The reasearch paper “Open source variational quantum eigensolver extension of the quantum learning machine for quantum chemistry” is now available on Wiley Journal! This release grants some following highlights include:

The paper introduces the OpenVQE open-source package, which extends the Atos Quantum Learning Machine (QLM) to provide advanced tools for using and developing variational quantum eigensolver (VQE) algorithms for quantum chemistry applications.
Present quantum processing units (QPUs) have limited qubit counts and circuit depths due to large errors, and VQE algorithms can potentially overcome such issues.
The OpenVQE package is designed to work synergistically with the myQLM-fermion open-source module, which provides key QLM resources important for quantum chemistry developments.
OpenVQE focuses on giving access to modules enabling the use of the unitary coupled cluster (UCC) family of methods and adaptive ansatz algorithms like ADAPT-VQE.
The UCC family modules in OpenVQE include various features such as different types of UCC generators, including UCCSD, k-UpCCGSD, and QUCCSD.
The adaptive VQE algorithms include fermionic-ADAPT-VQE and qubit-ADAPT-VQE, with different operator pools.
The paper presents extensive benchmarks using the OpenVQE/myQLM-fermion package on a range of molecules from 4 to 24 qubits, demonstrating the use of active space selection, MP2 pre-screening initial guesses, and comparing the fermionic and qubit-ADAPT-VQE results.
The paper compares the “fixed-length” UCC methods to the ADAPT-VQE approach, showing that ADAPT-VQE can achieve higher accuracy with fewer parameters and gates, depending on the chosen convergence threshold.
The paper emphasizes the open-source nature of the OpenVQE/myQLM-fermion packages, facilitating their use and contribution by the broader community, and provides perspectives for developing new types of UCC ansätze and/or new variational algorithms within OpenVQE.

Introduction to OpenVQE package

This paper introduces the OpenVQE open-source package, which extends the Atos Quantum Learning Machine (QLM) to provide advanced tools for using and developing variational quantum eigensolver (VQE) algorithms for quantum chemistry applications. The paper highlights that present quantum processing units (QPUs) have limited qubit counts and circuit depths due to large errors, and that VQE algorithms can potentially overcome such issues.

Design of the OpenVQE package

The UCC family modules in OpenVQE include various features such as different types of UCC generators (truncated to single and double excitations), including unitary coupled cluster singles and doubles (UCCSD), unitary pair CC with generalized singles and doubles product (k-UpCCGSD), and qubit unitary coupled cluster singles and doubles (QUCCSD). The adaptive VQE algorithms include fermionic-ADAPT-VQE and qubit-ADAPT-VQE, with different operator pools.

Benchmarking using OpenVQE/myQLM-fermion package

The paper presents extensive benchmarks using the OpenVQE/myQLM-fermion package on a range of molecules from 4 to 24 qubits. It first shows the properties of the QLM simulator, including the timings for applying the UCCSD ansatz and measuring the Hamiltonian expectation value. It then demonstrates the use of active space selection and MP2 pre-screening initial guesses for different test molecules. Using the ADAPT-VQE module, it compares the fermionic and qubit-ADAPT-VQE results in terms of chemical accuracy, number of variational parameters, operators, and quantum gates. Finally, it compares the “fixed-length” UCC methods to the ADAPT-VQE approach, showing that ADAPT-VQE can achieve higher accuracy with fewer parameters and gates, depending on the chosen convergence threshold.