Quantum Computing’s Potential in Chemistry Limited by Basis Sets and Ansatze, Study Finds

Quantum computing, with its potential to outperform existing algorithms, holds significant promise for computational and theoretical chemistry, according to researchers from the State University of Campinas. Despite current limitations, such as noise altering quantum states, the variational quantum eigensolver (VQE) algorithm is suitable for noisy-intermediate-scale-quantum (NISQ) hardware. The study investigates the role of basis sets and ansatze, like the unitary coupled-cluster (UCC), in quantum computing. However, only the smallest molecules and basis sets are currently tractable. Despite these challenges, the rapid development of the field suggests potential breakthroughs in the future.

What is the Impact of Basis Sets and Ansatze on Quantum Computing in Chemistry?

Quantum computing is a rapidly evolving field that holds significant promise for various sectors, including computational and theoretical chemistry. This article, authored by Caio Moraes Porto, Rene Alfonso Nome, and Nelson Henrique Morgon from the State University of Campinas, delves into the influence of basis sets and ansatze on quantum computing in chemistry.

Understanding Quantum Computing and Its Relevance in Chemistry

Quantum computing leverages the unique properties of quantum mechanics, such as superposition, entanglement, interference, and tunneling, to perform computational operations. This approach has the potential to significantly outperform existing algorithms designed for classical computers. However, the current state of quantum computing, known as the noisy-intermediate-scale-quantum (NISQ), is still not close to surpassing classical algorithms for most applications. The main limitation is noise, which can alter the quantum states of the qubits (quantum bits) and lead to a loss of quantum coherence.

Despite these challenges, quantum computing is particularly promising for computational and theoretical chemistry. One algorithm that has received significant attention is the variational quantum eigensolver (VQE). This algorithm is used to solve electronic structure problems and is suitable for NISQ hardware.

The Role of Basis Sets and Ansatze in Quantum Computing

In quantum computing, calculations require ansatze, and one of the most known is the unitary coupled-cluster (UCC). It uses the chosen basis set to generate a circuit, which is then iteratively minimized. The present work investigates the circuit depth as a function of basis sets and molecular size.

The researchers found that for the current quantum devices, only the smallest molecules and basis sets are tractable. For instance, the H2 molecule with the ccpVTZ and aug-cc-pVTZ basis sets have circuit depths in the order of 106 to 107 gates, and the C2H6 molecule with 321G basis set has a circuit depth of 22108 gates.

The Limitations and Future Prospects of Quantum Computing in Chemistry

While quantum computing holds significant promise for chemistry, the current limitations of the technology mean that only the smallest molecules and basis sets are currently tractable. Furthermore, error mitigation schemes, while able to reduce the error, were not able to completely negate it.

Despite these challenges, the rapid development of the field suggests that quantum computing may soon be able to fulfill the high expectations set for it. The race between classical and quantum computers has spurred the development of classical simulation techniques and algorithms, which could potentially lead to breakthroughs in the field.

In conclusion, while quantum computing is still in its nascent stages, its potential applications in chemistry are vast. The influence of basis sets and ansatze on quantum computing in chemistry is a crucial area of research that could pave the way for significant advancements in the field.