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Nanotechnol."],"published-print":{"date-parts":[[2025,4]]},"abstract":"<jats:title>Abstract<\/jats:title>\n          <jats:p>The intrinsic valley degree of freedom makes bilayer graphene (BLG) a unique platform for semiconductor qubits. The single-carrier quantum dot (QD) ground state exhibits a twofold degeneracy, where the two states that constitute a Kramers pair have opposite spin and valley quantum numbers. Because of the valley-dependent Berry curvature, an out-of-plane magnetic field breaks the time-reversal symmetry of this ground state and a qubit can be encoded in the spin\u2013valley subspace. The Kramers states are protected against known spin- and valley-mixing mechanisms because mixing requires a simultaneous change of the two quantum numbers. Here, we fabricate a tunable QD device in Bernal BLG and measure a spin\u2013valley relaxation time for the Kramers states of 38\u2009s at 30\u2009mK, which is two orders of magnitude longer than the 0.4\u2009s measured for purely spin-blocked states. We also show that the intrinsic Kane\u2013Mele spin\u2013orbit splitting enables a Kramers doublet single-shot readout even at zero magnetic field with a fidelity above 99%. If these long-lived Kramers states also possess long coherence times and can be effectively manipulated, electrostatically defined QDs in BLG may serve as long-lived semiconductor qubits, extending beyond the spin qubit paradigm.<\/jats:p>","DOI":"10.1038\/s41565-025-01858-8","type":"journal-article","created":{"date-parts":[[2025,2,10]],"date-time":"2025-02-10T10:03:42Z","timestamp":1739181822000},"page":"494-499","update-policy":"https:\/\/doi.org\/10.1007\/springer_crossmark_policy","source":"Crossref","is-referenced-by-count":25,"title":["Spin\u2013valley protected Kramers pair in bilayer graphene"],"prefix":"10.1038","volume":"20","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-9095-1579","authenticated-orcid":false,"given":"Artem O.","family":"Denisov","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Veronika","family":"Reckova","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Solenn","family":"Cances","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4776-699X","authenticated-orcid":false,"given":"Max J.","family":"Ruckriegel","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1663-8239","authenticated-orcid":false,"given":"Michele","family":"Masseroni","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Christoph","family":"Adam","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Chuyao","family":"Tong","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4164-8765","authenticated-orcid":false,"given":"Jonas D.","family":"Gerber","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9996-6371","authenticated-orcid":false,"given":"Wei Wister","family":"Huang","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3701-8119","authenticated-orcid":false,"given":"Kenji","family":"Watanabe","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1467-3105","authenticated-orcid":false,"given":"Takashi","family":"Taniguchi","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5587-6953","authenticated-orcid":false,"given":"Thomas","family":"Ihn","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7007-6949","authenticated-orcid":false,"given":"Klaus","family":"Ensslin","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0506-126X","authenticated-orcid":false,"given":"Hadrien","family":"Duprez","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"297","published-online":{"date-parts":[[2025,2,10]]},"reference":[{"key":"1858_CR1","doi-asserted-by":"publisher","first-page":"025003","DOI":"10.1103\/RevModPhys.95.025003","volume":"95","author":"G Burkard","year":"2023","unstructured":"Burkard, G., Ladd, T. 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