Quantum Simulation of Actinide Chemistry Achieves Scalable Algorithms on Trapped Ion Quantum Computers with 19 Qubits

Actinide elements underpin a wide range of technologies, and a detailed understanding of their electronic structure promises further advancements in numerous fields. Kesha Sorathia, Cono Di Paola, and Gabriel Greene-Diniz, all from Quantinuum, alongside colleagues, now demonstrate a significant step towards achieving this understanding through quantum simulation. The team develops and implements algorithms on trapped ion quantum computers to model the complex behaviour of plutonium oxides and hydrides, offering a potential pathway to overcome the limitations of classical computational methods. By employing techniques to minimise resource demands and utilising up to nineteen qubits on Quantinuum’s H-series devices, they achieve results that closely match established classical calculations, paving the way for scalable quantum simulations of complex chemical systems and offering new insights into actinide chemistry.

Quantum Simulations of Plutonium and Hydrides

Scientists are pioneering new methods to investigate the electronic structure of actinide elements, focusing on plutonium and its hydrides, using quantum computing and advanced quantum chemistry techniques. This research addresses the challenges posed by plutonium, a heavy element exhibiting strong relativistic effects and complex electronic interactions that traditional computational methods struggle to accurately model. The study utilizes several key computational tools and software packages, including Quantum ESPRESSO, Pyscf, and quantum computing platforms like t|ket⟩ and InQuanto. Researchers assess the precision of quantum simulations by calculating standard deviations, representing the uncertainty in calculated quantum state overlaps and providing a measure of the reliability of the results. These calculations are crucial for validating the accuracy of quantum simulations and comparing them to theoretical predictions and experimental data, representing a significant step towards improving calculations on plutonium compounds and establishing a robust framework for future investigations.

Quantum Computing Reveals Actinide Electronic Structure

Scientists have unlocked a new approach to understanding the electronic structure of actinide elements by harnessing the power of quantum computing, specifically focusing on plutonium oxides and hydrides. The study directly compares two quantum algorithms, Quantum Phase Estimation (QPE) and the method of Quantum Computed Moments (QCM), to determine reaction energetics with unprecedented precision. To adapt these algorithms for current quantum hardware, researchers implemented key innovations to reduce computational demands. They screened individual Hamiltonian Pauli terms, significantly reducing the number of measurements needed for QCM, and employed variational compilation to minimize the circuit depth of QPE circuits, a critical step for near-term quantum devices.

The team derived electronic structure descriptions from representative chemical models and then computed energetics using Quantinuum’s H-series ion trap devices, successfully utilizing up to nineteen qubits in their experiments. A single-ancilla version of QPE, combined with circuit recompilation, maintained constant circuit depth regardless of calculation complexity. Researchers also leveraged quantum subspace expansion, projecting the Schrödinger equation onto a finite subspace to create a low-dimensional eigenvalue problem solvable with classical methods. They measured Hamiltonian moments quantum mechanically and then classically diagonalized a Lanczos tridiagonalized form of the Hamiltonian to determine key energy values. The results demonstrate excellent agreement between quantum experiments, classical electronic structure calculations, and state vector simulations, validating the accuracy and potential of this quantum computational approach. This work establishes a pathway for accurately modelling strongly correlated actinide systems, overcoming limitations of traditional computational methods and offering new insights into their chemical behavior and potential applications in areas like energy generation and nuclear safety.

Actinide Energetics Simulated with Quantum Algorithms

Scientists have achieved a breakthrough in simulating the electronic structure of actinide elements using quantum computers, demonstrating a new approach to understanding these complex materials. The research team successfully applied two quantum algorithms, Quantum Phase Estimation (QPE) and Quantum Computed Moments (QCM), to model the energetics of plutonium oxides and hydrides using up to nineteen qubits on Quantinuum’s H-series trapped ion devices. Experiments utilizing QCM4, an expansion of the ground state energy in terms of Hamiltonian moments truncated to fourth order, describe electron correlation interactions inaccessible by traditional mean-field theories. The team employed a single-ancilla-qubit variant of QPE, known as the Quantum Complex Exponential Least Squares (QCELS) technique, combined with circuit recompilation to maintain constant circuit depth, addressing limitations of current quantum hardware.

Results from both QPE and QCM experiments demonstrate excellent agreement with classical electronic structure calculations and state vector simulations, validating the accuracy of the quantum approach. Specifically, the quantum simulations accurately model the energetics of plutonium compounds, providing insights into their behavior in oxidation and corrosion reactions. This work represents a significant advancement in applying quantum computing to actinide chemistry, offering a pathway to model complex systems previously intractable with classical methods. The successful implementation of these algorithms on real quantum hardware paves the way for future investigations into the electronic structure and reactivity of actinides, with potential applications in energy generation, nuclear safety, and materials science. The research confirms the potential of quantum computing to unlock a deeper understanding of these vital, yet challenging, materials.

Actinide Materials Modelled with Quantum Computation

This study demonstrates the successful application of quantum computation to model the electronic structure of actinide materials, a crucial step towards improving understanding and potential technological advancements in this field. Researchers compared two quantum algorithms, statistical quantum phase estimation and a quantum subspace expansion method, to simulate the energetics of plutonium oxides and hydrides, achieving excellent agreement with established classical calculations. Notably, the team performed the largest quantum phase estimation experiment to date for a quantum chemistry application, utilizing nineteen qubits and up to five hundred statistical precision counts. Complementary results were obtained using the quantum subspace expansion method, which provided accurate energies with relatively shallow quantum circuits.

However, this method’s requirement for a large number of measurements increased significantly with qubit count, potentially limiting its scalability without further optimization. The team acknowledges that increasing the complexity of the electronic structure problems. Therefore the depth of the required quantum circuits, presents a significant challenge given current limitations in quantum hardware coherence. Future research will focus on reducing the measurement overhead of the quantum subspace expansion method and exploring techniques to improve the quality of input states, potentially enabling larger and more complex simulations. Ultimately, realizing the full potential of these quantum chemistry methods requires continued advancements in quantum computing hardware, error correction, and algorithmic development.