Contribution from Anna Leonteva, Software Engineer at QPerfect
Many complex problems today — such as drug discovery and supply chain optimization — can be framed as optimization challenges, where the task is to identify the best solution among zillions of possibilities. However, traditional computing faces limits when the problem size becomes too large. Quantum computing has the potential to go beyond these limits by implementing Variational Quantum Algorithms, which use quantum principles to explore these vast solution spaces more efficiently.
Since today’s quantum computers are either too small or too noisy, showing quantum advantage at scale requires quantum emulators capable of handling large systems. As we show in this blogpost for the particular example of the Variational Quantum Eigensolver (VQE), QPerfect’s quantum emulator, MIMIQ, can simulate variational circuits of up to 100 qubits with high fidelity within minutes.
What is the Variational Quantum Eigensolver (VQE)?
VQE is an optimization algorithm which combines quantum and classical computing to find the lowest energy state of a quantum system. For example, in quantum chemistry, this lowest energy state represents a molecule’s most stable configuration. In finance, energy minimization translates into optimizing a portfolio to balance risk and return.
Benchmarking VQE scalability with MIMIQ
For small circuits (10-20 qubits), MIMIQ StateVector handles them very fast. For higher qubit numbers, MIMIQ automatically switches to MPS for faster simulations. The MPS runtime also increases as the qubit count grows, but much slower, allowing us to simulate circuits of up to 100 qubits within minutes.
Using MIMIQ’s default bond dimension of 256, the simulation is practically exact up to 40 qubits, and at bond dimension 512, MPS can simulate up to 60 qubits close to exactly, and 80 qubits with at least 80% overlap with the exact solution.
Conclusion
MIMIQ’s dual-engine approach enables efficient scaling of VQE across varying numbers of qubits. With MIMIQ, users can simulate small systems within milliseconds and tackle larger, complex systems — up to 100 qubits — in just minutes, while maintaining high fidelity.