{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,30]],"date-time":"2026-10-30T03:40:09Z","timestamp":1793331609297,"version":"4.5.0"},"reference-count":54,"publisher":"American Physical Society (APS)","issue":"11","license":[{"start":{"date-parts":[[2025,9,17]],"date-time":"2025-09-17T00:00:00Z","timestamp":1758067200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100000781","name":"European Research Council","doi-asserted-by":"publisher","award":["101118911"],"award-info":[{"award-number":["101118911"]}],"id":[{"id":"10.13039\/501100000781","id-type":"DOI","asserted-by":"publisher"}]},{"name":"Nanostructure Service Laboratory"}],"content-domain":{"domain":["journals.aps.org"],"crossmark-restriction":true},"short-container-title":["Phys. Rev. B"],"accepted":{"date-parts":[[2025,8,14]]},"abstract":"<jats:p>\n                    While transverse coupling (\n                    <a:math xmlns:a=\"http:\/\/www.w3.org\/1998\/Math\/MathML\">\n                      <a:msub>\n                        <a:mi>\u03c3<\/a:mi>\n                        <a:mi>x<\/a:mi>\n                      <\/a:msub>\n                    <\/a:math>\n                    ) is commonly used in qubit-resonator systems, longitudinal coupling via\n                    <b:math xmlns:b=\"http:\/\/www.w3.org\/1998\/Math\/MathML\">\n                      <b:msub>\n                        <b:mi>\u03c3<\/b:mi>\n                        <b:mi>z<\/b:mi>\n                      <\/b:msub>\n                    <\/b:math>\n                    presents a tantalizing alternative: it does not hybridize the modes, eliminating Purcell decay, and it enables quantum-nondemolition qubit readout independent of the qubit-resonator frequency detuning. Here, we demonstrate longitudinal coupling between a\n                    <c:math xmlns:c=\"http:\/\/www.w3.org\/1998\/Math\/MathML\">\n                      <c:mrow>\n                        <c:mo>{<\/c:mo>\n                        <c:msub>\n                          <c:mi>Cr<\/c:mi>\n                          <c:mn>7<\/c:mn>\n                        <\/c:msub>\n                        <c:mi>Ni<\/c:mi>\n                        <c:mo>}<\/c:mo>\n                      <\/c:mrow>\n                    <\/c:math>\n                    molecular spin qubit ensemble and the kinetic inductance of a granular aluminum superconducting microwave resonator. The inherent frequency independence of this coupling allows for the utilization of a 7.8-GHz readout resonator to measure the full\n                    <d:math xmlns:d=\"http:\/\/www.w3.org\/1998\/Math\/MathML\">\n                      <d:mrow>\n                        <d:mo>{<\/d:mo>\n                        <d:msub>\n                          <d:mi>Cr<\/d:mi>\n                          <d:mn>7<\/d:mn>\n                        <\/d:msub>\n                        <d:mi>Ni<\/d:mi>\n                        <d:mo>}<\/d:mo>\n                      <\/d:mrow>\n                    <\/d:math>\n                    magnetization curve spanning 0\u2013600\u00a0mT, corresponding to a spin frequency range of\n                    <e:math xmlns:e=\"http:\/\/www.w3.org\/1998\/Math\/MathML\">\n                      <e:mrow>\n                        <e:msub>\n                          <e:mi>f<\/e:mi>\n                          <e:mtext>spin<\/e:mtext>\n                        <\/e:msub>\n                        <e:mo>=<\/e:mo>\n                        <e:mn>0<\/e:mn>\n                      <\/e:mrow>\n                    <\/e:math>\n                    \u201315\u00a0GHz. For 2-GHz detuning from the readout resonator, we measure a\n                    <f:math xmlns:f=\"http:\/\/www.w3.org\/1998\/Math\/MathML\">\n                      <f:mrow>\n                        <f:mn>1<\/f:mn>\n                        <f:mo>\/<\/f:mo>\n                        <f:mi>e<\/f:mi>\n                      <\/f:mrow>\n                    <\/f:math>\n                    spin relaxation time of\n                    <g:math xmlns:g=\"http:\/\/www.w3.org\/1998\/Math\/MathML\">\n                      <g:mrow>\n                        <g:mi>\u03c4<\/g:mi>\n                        <g:mo>=<\/g:mo>\n                        <g:mn>0.38<\/g:mn>\n                      <\/g:mrow>\n                    <\/g:math>\n                    \u00a0s, limited by phonon decay to the substrate. Based on these results, we propose a path towards longitudinal coupling of single spins to a superconducting fluxonium qubit.\n                  <\/jats:p>","DOI":"10.1103\/jz24-qpqv","type":"journal-article","created":{"date-parts":[[2025,8,14]],"date-time":"2025-08-14T15:37:52Z","timestamp":1755185872000},"update-policy":"https:\/\/doi.org\/10.1103\/crossmark-policy","source":"Crossref","is-referenced-by-count":3,"title":["Kinetic inductance coupling for circuit QED with spins"],"prefix":"10.1103","volume":"112","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-7873-8644","authenticated-orcid":true,"given":"S.","family":"G\u00fcnzler","sequence":"first","affiliation":[{"id":[{"id":"https:\/\/ror.org\/04t3en479","id-type":"ROR","asserted-by":"publisher"}],"name":"Karlsruhe Institute of Technology"},{"id":[{"id":"https:\/\/ror.org\/04t3en479","id-type":"ROR","asserted-by":"publisher"}],"name":"Karlsruhe Institute of Technology"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6626-3901","authenticated-orcid":true,"given":"D.","family":"Rieger","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/04t3en479","id-type":"ROR","asserted-by":"publisher"}],"name":"Karlsruhe Institute of Technology"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8640-3270","authenticated-orcid":true,"given":"M.","family":"Spiecker","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/04t3en479","id-type":"ROR","asserted-by":"publisher"}],"name":"Karlsruhe Institute of Technology"},{"id":[{"id":"https:\/\/ror.org\/04t3en479","id-type":"ROR","asserted-by":"publisher"}],"name":"Karlsruhe Institute of Technology"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0001-0381-0653","authenticated-orcid":true,"given":"T.","family":"Koch","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/04t3en479","id-type":"ROR","asserted-by":"publisher"}],"name":"Karlsruhe Institute of Technology"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0966-0315","authenticated-orcid":true,"given":"G. 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All rights are reserved, including those for text and data mining, AI training, and similar technologies.","name":"copyright_statement","label":"Copyright statement","group":{"name":"copyright","label":"copyright"}},{"value":"2025","name":"copyright_year","label":"Copyright year","group":{"name":"copyright","label":"copyright"}},{"value":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/","name":"creative_commons_license","label":"Creative Commons license","group":{"name":"licenses","label":"Licenses"}},{"value":"\u00a92025 The authors","name":"copyright_holder","label":"Copyright holder","group":{"name":"copyright","label":"copyright"}}],"article-number":"115424"}}