Santana Lujan | Searcharxiv

arXiv2026

Dynamical Decoupling using Universal Optimal Tracking

Dynamical decoupling (DD) is a widely used and resource-efficient technique for error suppression, but conventional DD relies on periodically repeating a short pulse block to refocus the qubit state during idle periods. Imperfections in this block cause residual errors to accumulate, ultimately degrading state recovery over long idle times. Here, we introduce a universal optimal tracking approach that extends the original tracking concept to a fully state-independent setting for designing DD sequences. By monitoring the qubit's evolution at predefined waypoints during optimization, the method dynamically compensates residual errors while preserving regular refocusing. Experimental demonstrations on a superconducting-qubit platform confirm the suppression of error accumulation under static control imperfections, in agreement with numerical predictions. Complementary simulations further show that optimal-tracking-based sequences maintain strong performance under time-dependent noise. These results establish optimal tracking as a practical and hardware-agnostic approach to designing short, robust DD sequences suitable for noisy quantum devices.

quant-ph↗

arXiv2025

Tackling the Challenges of Adding Pulse-level Support to a Heterogeneous HPCQC Software Stack: MQSS Pulse

We study the problem of adding native pulse-level control to heterogeneous High Performance Computing-Quantum Computing (HPCQC) software stacks, using the Munich Quantum Software Stack (MQSS) as a case study. The goal is to expand the capabilities of HPCQC environments by offering the ability for low-level access and control, currently typically not foreseen for such hybrid systems. For this, we need to establish new interfaces that integrate such pulse-level control into the lower layers of the software stack, including the need for proper representation. Pulse-level quantum programs can be fully described with only three low-level abstractions: ports (input/output channels), frames (reference signals), and waveforms (pulse envelopes). We identify four key challenges to represent those pulse abstractions at: the user-interface level, at the compiler level (including the Intermediate Representation (IR)), and at the backend-interface level (including the appropriate exchange format). For each challenge, we propose concrete solutions in the context of MQSS. These include introducing a compiled (C/C++) pulse Application Programming Interface (API) to overcome Python runtime overhead, extending its LLVM support to include pulse-related instructions, using its C-based backend interface to query relevant hardware constraints, and designing a portable exchange format for pulse sequences. Our integrated approach provides an end-to-end path for pulse-aware compilation and runtime execution in HPCQC environments. This work lays out the architectural blueprint for extending HPCQC integration to support pulse-level quantum operations without disrupting state-of-the-art classical workflows.

quant-ph↗