@article{wilson_mueller_pakin_2022, title={Combining Hard and Soft Constraints in Quantum Constraint-Satisfaction Systems}, ISSN={["2167-4329"]}, DOI={10.1109/SC41404.2022.00018}, abstractNote={This work presents a generalization of NchooseK, a constraint satisfaction system designed to target both quantum circuit devices and quantum annealing devices. Previously, NchooseK supported only hard constraints, which made it suitable for expressing problems in NP (e.g., 3-SAT) but not NP-hard problems (e.g., minimum vertex cover). In this paper we show how support for soft constraints can be added to the model and implementation, broadening the classes of problems that can be expressed elegantly in NchooseK without sacrificing portability across different quantum devices. Through a set of examples, we argue that this enhanced version of NchooseK enables problems to be expressed in a more concise, less error-prone manner than if these problems were encoded manually for quantum execution. We include an empirical evaluation of performance, scalability, and fidelity on both a large IBM Q system and a large D- Wave system.}, journal={SC22: INTERNATIONAL CONFERENCE FOR HIGH PERFORMANCE COMPUTING, NETWORKING, STORAGE AND ANALYSIS}, author={Wilson, Ellis and Mueller, Frank and Pakin, Scott}, year={2022} }
 @article{wilson_mueller_pakin_2021, title={Mapping Constraint Problems onto Quantum Gate and Annealing Devices}, DOI={10.1109/QCS54837.2021.00016}, abstractNote={This work presents NchooseK, a unified programming model for constraint satisfaction problems that can be mapped to both quantum circuit and annealing devices through Quadratic Unconstrained Binary Operators (QUBOs). Our mapping provides an approachable and effective way to program both types of quantum computers. We provide examples of NchooseK being used.}, journal={PROCEEDINGS OF SECOND INTERNATIONAL WORKSHOP ON QUANTUM COMPUTING SOFTWARE (QCS 2021)}, author={Wilson, Ellis and Mueller, Frank and Pakin, Scott}, year={2021}, pages={110–117} }
 @article{wilson_singh_mueller_2020, title={Just-in-time Quantum Circuit Transpilation Reduces Noise}, DOI={10.1109/QCE49297.2020.00050}, abstractNote={Running quantum programs is fraught with challenges on on today's noisy intermediate scale quantum (NISQ) devices. Many of these challenges originate from the error characteristics that stem from rapid decoherence and noise during measurement, qubit connections, crosstalk, the qubits themselves, and transformations of qubit state via gates. Not only are qubits not “created equal”, but their noise level also changes over time. IBM is said to calibrate their quantum systems once per day and reports noise levels (errors) at the time of such calibration. This information is subsequently used to map circuits to higher quality qubits and connections up to the next calibration point. This work provides evidence that there is room for improvement over this daily calibration cycle. It contributes a technique to measure noise levels (errors) related to qubits immediately before executing one or more sensitive circuits and shows that just-in-time noise measurements can benefit late physical qubit mappings. With this just-in-time recalibrated transpilation, the fidelity of results is improved over IBM's default mappings, which only uses their daily calibrations. The framework assess two major sources of noise, namely readout errors (measurement errors) and two-qubit gate/connection errors. Experiments indicate that the accuracy of circuit results improves by 3–304% on average and up to 400% with on-the-fly circuit mappings based on error measurements just prior to application execution.}, journal={IEEE INTERNATIONAL CONFERENCE ON QUANTUM COMPUTING AND ENGINEERING (QCE20)}, author={Wilson, Ellis and Singh, Sudhakar and Mueller, Frank}, year={2020}, pages={345–355} }