  We present the Quantum Monte Carlo Integration (QMCI) engine developed by
Quantinuum. It is a quantum computational tool for evaluating multi-dimensional
integrals that arise in various fields of science and engineering such as
finance. This white paper presents a detailed description of the architecture
of the QMCI engine, including a variety of distribution-loading methods, a
novel quantum amplitude estimation method that improves the statistical
robustness of QMCI calculations, and a library of statistical quantities that
can be estimated. The QMCI engine is designed with modularity in mind, allowing
for the continuous development of new quantum algorithms tailored in particular
to financial applications. Additionally, the engine features a resource mode,
which provides a precise resource quantification for the quantum circuits
generated. The paper also includes extensive benchmarks that showcase the
engine's performance, with a focus on the evaluation of various financial
instruments.
