We introduce a cost-effective quantum error mitigation technique that builds upon the recent Ansatz-based gate and readout error mitigation method (M0). The technique, tiled M0, leverages the unique structure of tiled Ansätze (e.g., tUPS, QNP, and hardware-efficient circuits) to apply a locality approximation to M0 that results in an exponential reduction in the QPU cost of the noise characterization. We validate the technique for molecular ground-state energy calculations with the tUPS Ansatz on LiH, H2, H2O, butadiene, and benzene (4-12 qubits), demonstrating little to no loss in accuracy compared to M0 in noisy simulations. We also show the performance of the technique in quantum experiments, highlighting its potential use in near-term applications.
Oskar Graulund Lentz Rasmussen, Erik Kjellgren, Peter Reinholdt et al.· Journal of Chemical Theory a...· 4 citations
G-quadruplexes are structurally diverse nucleic acid motifs with important biological properties as well as emerging applications in biotechnology and therapeutics. Here, we investigate whether a double-headed bis-guanine (G) nucleotide, GG-a substantial deviation from canonical nucleic acid architecture-can be accommodated within G-quadruplex structures and how its effects depend on sequence context and topology. Using a combination of circular dichroism (CD) spectroscopy, thermal denaturation analysis, UV thermal differential spectroscopy (TDS), fluorescence light-up assays, polyacrylamide gel electrophoresis (PAGE) analysis, and molecular dynamics (MD) simulations, we show that GG can substitute two consecutive guanosines in G-quadruplex-forming oligonucleotides (ONs) and directly participate in G-tetrad formation, but with strong sequence- and position-dependent consequences. GG incorporation is best tolerated in parallel G-quadruplexes and at G-tetrad steps with low native torsional twist, where local unwinding can be accommodated. In a tetramolecular TG4T system, GG positioned near the 3'-end of the G-stack preserved parallel G-quadruplex topology while providing significant thermal stabilization (+21°C). In the antiparallel thrombin-binding aptamer (TBA), a single GG incorporation yielded exceptional stabilization (+34°C) but was accompanied by altered topological signatures. Together, the results presented herein establish GG as a powerful but context-dependent G-quadruplex stabilizer and define design principles for its use in engineered G-quadruplexes and aptamer development.
Krista Urup, Peter Reinholdt, Kasper M. Beck et al.· Chemistry· 0 citations
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