As the capabilities of quantum computing hardware continue to rise, algorithms that exploit them are becoming increasingly complex. These developments increase the need for sophisticated compilation frameworks that translate high-level algorithms into executable code. In the past, most solutions were built with a quantum-first approach and handled mostly pure quantum programs without classical elements such as structured control flow. However, developments in quantum algorithms, error correction, and optimization, as well as the integration into high-performance computing (HPC) environments, depend on such classical elements. As quantum-first approaches increasingly struggle to handle these concepts, classical-first approaches are becoming a promising alternative. In this work, we present the MQT Compiler Collection, a blueprint for a future-proof quantum-classical compilation framework built on the Multi-Level Intermediate Representation (MLIR). After years of experience with the quantum-first approach and its shortcomings, we propose a framework that embraces core MLIR concepts to support the full compilation pipeline from high-level algorithms to hardware-specific instructions. The proposed architecture is designed from the ground up to support complex optimizations beyond, e.g., simple gate cancellation. It is publicly available at github.com/munich-quantum-toolkit/core.

Superconducting quantum computers are fundamentally limited by restricted qubit connectivity. Bus-resonator architectures alleviate this constraint by enabling effective all-to-all interactions. This advantage, however, comes at the cost of significant operational overhead. Realizing the full potential of such hardware thus requires sophisticated compilation techniques that minimize this overhead. In this work, we present the first formalization of the underlying compilation problem for bus-resonator architectures amenable to so-called SAT-CP solvers. This formalization yields optimal solutions for small quantum circuits. For larger instances, we propose a linear-time heuristic. Experimental evaluations confirm that the formalization makes it possible to find optimal solutions even in vast search spaces and that the heuristic provides near-optimal compilation while scaling efficiently to circuits of practical size. Together, these contributions establish both a rigorous baseline and a practical path toward low-overhead compilation for superconducting bus-resonator devices.

Quantum computing is becoming a reality. Superconducting, ion traps, neutral atoms, etc.—the hardware is getting there! However, software capable of handling complex design tasks is needed to connect end users to these platforms. Unfortunately, software for quantum computing is still in its infancy, and the development of quantum computing software remains a significant challenge. The MQSC aims to create production-ready software tools that provide for quantum computing what we already take for granted in classical IT.

Quantum computing is an emerging technology that has seen significant software and hardware improvements in recent years. Executing a quantum program requires the compilation of its quantum circuit for a target Quantum Processing Unit (QPU). Various methods for qubit mapping, gate synthesis, and optimization of quantum circuits have been proposed and implemented in compilers. These compilers try to generate a quantum circuit that leads to the best execution quality-a criterium which is usually approximated by figures of merit such as the number of (two-qubit) gates, the circuit depth, expected fidelity, or estimated success probability. However, it is often unclear how well these figures of merit represent the actual execution quality on a QPU. In this work, we investigate the correlation between established figures of merit and actual execution quality on real machines-revealing that the correlation is weaker than anticipated and that more complex figures of merit are not necessarily more accurate. Motivated by this finding, we propose an improved figure of merit (based on a machine learning approach) that can be used to predict the expected execution quality of a quantum circuit for a chosen QPU without actually executing it. The employed machine learning model reveals the influence of various circuit features on generating high correlation scores. The proposed figure of merit demonstrates a strong correlation and outperforms all previous ones in a case study-achieving an average correlation improvement of 49%.