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Limitations of quantum hardware for molecular energy estimation using VQE
Abel Carreras1, Román Orús1,2,3, David Casanova1,2
1Donostia International Physics Center (DIPC), 20018 Donostia, Euskadi, Spain. abelcarreras83@gmail.com.
Physical Chemistry Chemical Physics : PCCP
|January 13, 2026
Summary
Variational quantum eigensolvers (VQE) show promise for quantum chemistry but face limitations on current hardware. Noise and hardware constraints prevent accurate molecular energy calculations, necessitating future advancements for practical applications.
Area of Science:
- Quantum Computing
- Computational Chemistry
- Quantum Algorithms
Background:
- Variational quantum eigensolvers (VQE) are key quantum algorithms for electronic structure problems.
- The noisy intermediate-scale quantum (NISQ) era presents challenges for VQE implementation.
- Accurate determination of molecular ground-state energies is crucial for quantum chemistry.
Purpose of the Study:
- Investigate VQE capabilities and limitations on current quantum hardware.
- Focus on the adaptive derivative-assembled pseudo-Trotter ansatz VQE (ADAPT-VQE).
- Assess the impact of quantum noise and hardware limitations on accuracy.
Main Methods:
- Explored strategies to simplify molecular Hamiltonians.
- Optimized the ansatz and classical parameter optimization (COBYLA).
- Implemented tailored quantum computing to minimize circuit depth and cost, tested on an IBM quantum computer using benzene.
Main Results:
- Optimizations were applied to VQE implementation.
- Current quantum hardware noise significantly impacts state preparation and energy measurement.
- Achieved accuracy is insufficient for reliable quantum chemical insights.
Conclusions:
- Current quantum hardware limitations, primarily noise, prevent accurate molecular energy calculations with VQE.
- Future quantum hardware must meet specific requirements for scalable quantum chemistry.
- This study assesses VQE on real hardware, highlighting noise and accuracy challenges.
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