Iterative Phase Optimization of Elementary Quantum Error Correcting Codes

Performing experiments on small-scale quantum computers is certainly a challenging endeavor. Many parameters need to be optimized to achieve high-fidelity operations. This can be done efficiently for operations acting on single qubits, as errors can be fully characterized. For multiqubit operations, though, this is no longer the case, as in the most general case, analyzing the effect of the operation on the system requires a full state tomography for which resources scale exponentially with the system size. Furthermore, in recent experiments, additional electronic levels beyond the two-level system encoding the qubit have been used to enhance the capabilities of quantum-information processors, which additionally increases the number of parameters that need to be controlled. For the optimization of the experimental system for a given task (e.g., a quantum algorithm), one has to find a satisfactory error model and also efficient observables to estimate the parameters of the model. In this manuscript, we demonstrate a method to optimize the encoding procedure for a small quantum error correction code in the presence of unknown but constant phase shifts. The method, which we implement here on a small-scale linear ion-trap quantum computer, is readily applicable to other AMO platforms for quantum-information processing.

El discurso político en el contexto multicultural de las instituciones de la Unión Europea. El discurso político en español y en polaco

The comparative analysis of Polish and Spanish political discourse in the multilingual context of European institutions is challenging not only due to linguistic, cultural, geopolitical and social differences, but also because of a relatively short history of such contacts in the EU framework. Intercultural communication, as a dynamic social practice is a fascinating object of investigation. Bidirectional comparative analysis of Polish and Spanish oral texts allows define the barriers of such communication. It encompasses the discursive act together with its objectives, strategies and consequences, and also its raison d’être. It explains why different strategies reflected through discursive categories were used. Consequently it describes both, conditions and outcomes of identity negotiation. The latter is a political competence perceived and evaluated by the direct interlocutors, the participants of the political debate, and indirectly, by a public opinion of the European Union. That proves it is two-level communication. The negotiation of political identity through discourse, according to the Ting-Toomey theory, can lead to maintaining, loosing, recovering or reinforcing it282. The Identity Negotiation Theory includes the construction and development of personal, relational, role and desired identity and is one of the methodological axes of this investigation. Political identity consists of exhibiting necessary competences to efficiently participate in the legislation process, for example, in order to present amendments, promote a given ideology, participate in controversial discussions and manage conflicts, and, finally, gain the support of public opinion. The analysis of creation, negotiation, maintenance, recovery and promotion of the political identity is performed through the identification and description of discursive categories proposed by Van Dijk283 and adapted to the needs of this study. This is the second methodological axe of the investigation. The following questions arise: which discursive strategies, used by Polish and Spanish politicians, will be communication facilitators and which will be barriers hampering communication? Which strategies show political competencies of the speaker, his or her influence in the legal EU reality through discourse?...