{"id":778847,"date":"2026-05-07T04:43:24","date_gmt":"2026-05-07T04:43:24","guid":{"rendered":"https:\/\/www.europesays.com\/us\/778847\/"},"modified":"2026-05-07T04:43:24","modified_gmt":"2026-05-07T04:43:24","slug":"quantum-coherent-manipulation-and-readout-of-superconducting-vortex-states","status":"publish","type":"post","link":"https:\/\/www.europesays.com\/us\/778847\/","title":{"rendered":"Quantum coherent manipulation and readout of superconducting vortex states"},"content":{"rendered":"<p>From the moment of its discovery, the antagonistic relation between superconductivity and a magnetic field has provided a complex playground for experimentalists and theorists alike. The measurement of the critical field and the Meissner effect<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 12\" title=\"Meissner, W. &amp; Ochsenfeld, R. Ein neuer Effekt bei Eintritt der Supraleitf&#xE4;higkeit. Naturwissenschaften 21, 787 (1933).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR12\" id=\"ref-link-section-d97029111e680\" rel=\"nofollow noopener\" target=\"_blank\">12<\/a> have anchored phase-transition theories<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 13\" title=\"London, F., London, H. &amp; Lindemann, F. A. The electromagnetic equations of the supraconductor. Proc. R. Soc. Lond. Ser. A 149, 71&#x2013;88 (1935).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR13\" id=\"ref-link-section-d97029111e684\" rel=\"nofollow noopener\" target=\"_blank\">13<\/a>,<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 14\" title=\"Ginzburg, V. L. &amp; Landau, L. D. in On Superconductivity and Superfluidity: A Scientific Autobiography (ed. Ginzburg, V. L.) 113&#x2013;137 (Springer, 2009).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR14\" id=\"ref-link-section-d97029111e687\" rel=\"nofollow noopener\" target=\"_blank\">14<\/a>, and the trapping of quantized flux inside superconductors has provided direct evidence for the existence of Cooper pairs<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 15\" title=\"Tinkham, M. Introduction to Superconductivity (Courier Corporation, 2004).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR15\" id=\"ref-link-section-d97029111e691\" rel=\"nofollow noopener\" target=\"_blank\">15<\/a>. A hallmark of type II superconductivity in a magnetic field is the formation of Abrikosov vortices: regions of local gap suppression that interact to form lattices<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 1\" title=\"Abrikosov, A. A. On the magnetic properties of superconductors of the second group. Sov. Phys. JETP 5, 1174 (1957).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR1\" id=\"ref-link-section-d97029111e695\" rel=\"nofollow noopener\" target=\"_blank\">1<\/a>. Vortex dynamics is detrimental for a wide range of applications<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 15\" title=\"Tinkham, M. Introduction to Superconductivity (Courier Corporation, 2004).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR15\" id=\"ref-link-section-d97029111e699\" rel=\"nofollow noopener\" target=\"_blank\">15<\/a>, causing heating, flux noise and magnetic hysteresis. However, pinned vortices enable quasiparticle trapping in their core, which enhances the critical current<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 16\" title=\"Hebard, A., Fiory, A. &amp; Somekh, S. Critical currents in Al films with a triangular lattice of 1 &#x3BC;m holes. IEEE Trans. Magn. 13, 589&#x2013;592 (1977).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR16\" id=\"ref-link-section-d97029111e704\" rel=\"nofollow noopener\" target=\"_blank\">16<\/a> of superconducting films, improves micro-cooler efficiency<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 17\" title=\"Peltonen, J. T., Muhonen, J. T., Meschke, M., Kopnin, N. B. &amp; Pekola, J. P. Magnetic-field-induced stabilization of nonequilibrium superconductivity in a normal-metal\/insulator\/superconductor junction. Phys. Rev. B 84, 220502 (2011).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR17\" id=\"ref-link-section-d97029111e708\" rel=\"nofollow noopener\" target=\"_blank\">17<\/a>, boosts resonator quality factors<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 18\" title=\"Nsanzineza, I. &amp; Plourde, B. Trapping a single vortex and reducing quasiparticles in a superconducting resonator. Phys. Rev. Lett. &#010;                  https:\/\/doi.org\/10.1103\/physrevlett.113.117002&#010;                  &#010;                 (2014).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR18\" id=\"ref-link-section-d97029111e712\" rel=\"nofollow noopener\" target=\"_blank\">18<\/a> and improves qubit coherence<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 19\" title=\"Wang, C. et al. Measurement and control of quasiparticle dynamics in a superconducting qubit. Nat. Commun. 5, 5836 (2014).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR19\" id=\"ref-link-section-d97029111e716\" rel=\"nofollow noopener\" target=\"_blank\">19<\/a>,<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 20\" title=\"Vool, U. et al. Non-Poissonian quantum jumps of a fluxonium qubit due to quasiparticle excitations. Phys. Rev. Lett. 113, 247001 (2014).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR20\" id=\"ref-link-section-d97029111e719\" rel=\"nofollow noopener\" target=\"_blank\">20<\/a>. In all these cases, owing to the normal state core, vortices can be understood within semi-classical models.<\/p>\n<p>Gap suppression in the vortex core stems from the crowding of supercurrent at its centre, a consequence of continuity in the superconducting medium. Recent work<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 3\" title=\"Kiselov, D., Skvortsov, M. A. &amp; Feigel&#x2019;man, M. V. Gapful electrons in a vortex core in granular superconductors. SciPost Phys. &#010;                  https:\/\/doi.org\/10.21468\/scipostphys.15.1.008&#010;                  &#010;                 (2023).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR3\" id=\"ref-link-section-d97029111e726\" rel=\"nofollow noopener\" target=\"_blank\">3<\/a> has proposed that in discretized systems, such as granular superconductors where non-superconducting regions separate superconducting islands, the vortex core can remain gapped and dissipationless; a closely related regime has also been predicted for strongly disordered superconductors, where emergent superconducting islands<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 2\" title=\"Bouadim, K., Loh, Y. L., Randeria, M. &amp; Trivedi, N. Single- and two-particle energy gaps across the disorder-driven superconductor&#x2013;insulator transition. Nat. Phys. 7, 884&#x2013;889 (2011).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR2\" id=\"ref-link-section-d97029111e730\" rel=\"nofollow noopener\" target=\"_blank\">2<\/a> host vortices with insulating cores<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 4\" title=\"Datta, A., Banerjee, A., Trivedi, N. &amp; Ghosal, A. Insulating vortex cores in disordered superconductors. Phys. Rev. B 107, L140502 (2023).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR4\" id=\"ref-link-section-d97029111e734\" rel=\"nofollow noopener\" target=\"_blank\">4<\/a>. Although quantum behaviour has been revealed by tunnelling of vortices in long Josephson junctions<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 8\" title=\"Wallraff, A. et al. Quantum dynamics of a single vortex. Nature 425, 155&#x2013;158 (2003).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR8\" id=\"ref-link-section-d97029111e738\" rel=\"nofollow noopener\" target=\"_blank\">8<\/a> and thin films<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 9\" title=\"Liu, Y., Haviland, D. B., Glazman, L. I. &amp; Goldman, A. M. Evidence for quantum tunneling of vortices in superconductors. J. Low Temp. Phys. 89, 187&#x2013;196 (1992).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR9\" id=\"ref-link-section-d97029111e742\" rel=\"nofollow noopener\" target=\"_blank\">9<\/a>, or via the zero-point motion of pinned vortices<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 10\" title=\"Dutta, S., Roy, I., Jesudasan, J., Sachdev, S. &amp; Raychaudhuri, P. Evidence of zero-point fluctuation of vortices in a very weakly pinned a-MoGe thin film. Phys. Rev. B 103, 214512 (2021).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR10\" id=\"ref-link-section-d97029111e747\" rel=\"nofollow noopener\" target=\"_blank\">10<\/a>, direct evidence of coherent superconducting vortex states has yet to be observed.<\/p>\n<p>Here we show that vortices trapped in a superconducting granular aluminium (grAl) microwave resonator form field-tunable two-level systems that behave like effective spins, strongly coupled to the resonator. They can therefore be regarded as quantum bits (qubits) that arise from vortex tunnelling in a field-modulated double-well potential formed between pinning sites. These vortex qubit (VQ) states exhibit microsecond coherence and energy relaxation times on the order of 102\u2009\u03bcs, strikingly different from the dissipative dynamics of Abrikosov vortices. We find that VQs remain stable for weeks, enabling coherent control and quantum non-demolition readout within the framework of circuit quantum electrodynamics<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 11\" title=\"Blais, A., Grimsmo, A. L., Girvin, S. M. &amp; Wallraff, A. Circuit quantum electrodynamics. Rev. Mod. Phys. 93, 025005 (2021).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR11\" id=\"ref-link-section-d97029111e756\" rel=\"nofollow noopener\" target=\"_blank\">11<\/a>.<\/p>\n<p>As schematized in Fig. <a data-track=\"click\" data-track-label=\"link\" data-track-action=\"figure anchor\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#Fig1\" rel=\"nofollow noopener\" target=\"_blank\">1<\/a>, we use a grAl micro-stripline resonator, with resistivity \u03c1\u00a0=\u00a03,600\u2009\u03bc\u03a9\u2009cm, chosen to be within a factor of 3 below the superconducting-to-insulating transition<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 21\" title=\"Levy-Bertrand, F. et al. Electrodynamics of granular aluminum from superconductor to insulator: observation of collective superconducting modes. Phys. Rev. B 99, 094506 (2019).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR21\" id=\"ref-link-section-d97029111e769\" rel=\"nofollow noopener\" target=\"_blank\">21<\/a>. In this regime, the film consists of Al grains of 3\u20134-nm diameter separated by amorphous AlOx barriers, resulting in a coherence length \u03be\u00a0\u2248\u00a07\u2009nm and London penetration depth of \u03bbL\u00a0\u2248\u00a04\u2009\u03bcm (refs. <a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 5\" title=\"Deutscher, G., Fenichel, H., Gershenson, M., Gr&#xFC;nbaum, E. &amp; Ovadyahu, Z. Transition to zero dimensionality in granular aluminum superconducting films. J. Low Temp. Phys. 10, 231&#x2013;243 (1973).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR5\" id=\"ref-link-section-d97029111e785\" rel=\"nofollow noopener\" target=\"_blank\">5<\/a>,<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 22\" title=\"Cohen, R. W. &amp; Abeles, B. Superconductivity in granular aluminum films. Phys. Rev. 168, 444&#x2013;450 (1968).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR22\" id=\"ref-link-section-d97029111e788\" rel=\"nofollow noopener\" target=\"_blank\">22<\/a>,<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 23\" title=\"Glezer Moshe, A., Farber, E. &amp; Deutscher, G. Granular superconductors for high kinetic inductance and low loss quantum devices. Appl. Phys. Lett. 117, 062601 (2020).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR23\" id=\"ref-link-section-d97029111e791\" rel=\"nofollow noopener\" target=\"_blank\">23<\/a>). The resonator is placed in a cylindrical copper waveguide (Supplementary Information section\u00a0<a data-track=\"click\" data-track-label=\"link\" data-track-action=\"supplementary material anchor\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#MOESM1\" rel=\"nofollow noopener\" target=\"_blank\">I<\/a>) anchored to the 20-mK base plate of a dilution cryostat and measured in reflection. When cooled in zero magnetic field Bcd\u00a0=\u00a00\u2009\u03bcT, the grAl resonator behaves as a weakly anharmonic oscillator<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 24\" title=\"Maleeva, N. et al. Circuit quantum electrodynamics of granular aluminum resonators. Nat. Commun. 9, 3889 (2018).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR24\" id=\"ref-link-section-d97029111e802\" rel=\"nofollow noopener\" target=\"_blank\">24<\/a>, with a fundamental frequency fr\u00a0=\u00a07.572\u2009GHz, set by its dimensions (3\u2009\u03bcm wide, 400\u2009\u03bcm long; Extended Data Fig. <a data-track=\"click\" data-track-label=\"link\" data-track-action=\"figure anchor\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#Fig5\" rel=\"nofollow noopener\" target=\"_blank\">1<\/a>). Figure <a data-track=\"click\" data-track-label=\"link\" data-track-action=\"figure anchor\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#Fig1\" rel=\"nofollow noopener\" target=\"_blank\">1b<\/a> shows the frequency decrease with perpendicular magnetic field B, as expected with the increase in kinetic inductance<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 25\" title=\"Annunziata, A. J. et al. Tunable superconducting nanoinductors. Nanotechnology 21, 445202 (2010).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR25\" id=\"ref-link-section-d97029111e820\" rel=\"nofollow noopener\" target=\"_blank\">25<\/a>,<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 26\" title=\"Borisov, K. et al. Superconducting granular aluminum resonators resilient to magnetic fields up to 1 tesla. Appl. Phys. Lett. &#010;                  https:\/\/doi.org\/10.1063\/5.0018012&#010;                  &#010;                 (2020).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR26\" id=\"ref-link-section-d97029111e823\" rel=\"nofollow noopener\" target=\"_blank\">26<\/a>.<\/p>\n<p><b id=\"Fig1\" class=\"c-article-section__figure-caption\" data-test=\"figure-caption-text\">Fig. 1: Field cooling introduces VQ states that couple to the grAl resonator.<\/b><img decoding=\"async\" aria-describedby=\"figure-1-desc ai-alt-disclaimer-figure-1-1\" src=\"https:\/\/www.europesays.com\/us\/wp-content\/uploads\/2026\/05\/41586_2026_10441_Fig1_HTML.png\" alt=\"Fig. 1: Field cooling introduces VQ states that couple to the grAl resonator.\" loading=\"lazy\" width=\"685\" height=\"570\"\/>The alternative text for this image may have been generated using AI.<\/p>\n<p><b>a<\/b>, When cooled to 20\u2009mK in perpendicular magnetic field Bcd\u00a0=\u00a00\u2009\u03bcT, a \u03bb\/2 micro-stripline grAl resonator behaves as a quantum harmonic oscillator\u00a0with resonant frequency\u00a0\u03c9r. The electric- and magnetic-field distributions are illustrated in blue and red, respectively.\u00a0The grAl film has a thickness of\u00a0t\u00a0= 20\u00a0nm and\u00a0a superconducting coherence length of \u03be\u00a0= 7\u00a0nm. <b>b<\/b>, Phase response arg(S11) of the resonator measured in reflection, as a function of perpendicular magnetic field B applied after cooling. The measured parabolic suppression of the resonance is given by the increase in kinetic inductance owing to screening currents<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 25\" title=\"Annunziata, A. J. et al. Tunable superconducting nanoinductors. Nanotechnology 21, 445202 (2010).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR25\" id=\"ref-link-section-d97029111e870\" rel=\"nofollow noopener\" target=\"_blank\">25<\/a>, and the field range is limited by the vortex penetration threshold<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 26\" title=\"Borisov, K. et al. Superconducting granular aluminum resonators resilient to magnetic fields up to 1 tesla. Appl. Phys. Lett. &#010;                  https:\/\/doi.org\/10.1063\/5.0018012&#010;                  &#010;                 (2020).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR26\" id=\"ref-link-section-d97029111e875\" rel=\"nofollow noopener\" target=\"_blank\">26<\/a>. <b>c<\/b>, When cooled in perpendicular magnetic field Bcd\u00a0=\u00a0820\u2009\u03bcT (see main text), vortices enter the grAl resonator and the system exhibits a behaviour akin to a flux qubit with a\u00a0transition frequency\u00a0\u03c9q\u00a0coupled to a readout resonator, as illustrated in <b>d<\/b> and <b>e<\/b>. <b>d<\/b>, The measured phase response of the resonator as a function of B reveals avoided level crossings, suggesting coupling to vortex states. The purple dashed line shows a fit to the asymmetric quantum Rabi model (equation (<a data-track=\"click\" data-track-label=\"link\" data-track-action=\"equation anchor\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#Equ2\" rel=\"nofollow noopener\" target=\"_blank\">2<\/a>)), yielding the coupling g\/2\u03c0\u00a0=\u00a095\u2009MHz. <b>e<\/b>, Extracted VQ frequency fq from two-tone spectroscopy (see inset) as a function of B. The green line corresponds to the joint fit of data in <b>d<\/b> and <b>e<\/b> to equation (<a data-track=\"click\" data-track-label=\"link\" data-track-action=\"equation anchor\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#Equ2\" rel=\"nofollow noopener\" target=\"_blank\">2<\/a>), and the purple dashed line marks the bare resonator frequency fr. Inset: two-tone spectroscopy in the vicinity of B0 corresponding to the minimum frequency of the VQ. The colour scale indicates the measured phase response as a function of the frequency fd of the second drive.<\/p>\n<p>Following field-cooling, sweeping B reveals avoided level crossings in the grAl resonator response as illustrated in Fig. <a data-track=\"click\" data-track-label=\"link\" data-track-action=\"figure anchor\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#Fig1\" rel=\"nofollow noopener\" target=\"_blank\">1d<\/a>, which we interpret as evidence of strong coupling with g\/2\u03c0\u00a0=\u00a095\u2009MHz to vortex states. To extract the mode\u2019s spectrum, we sweep a second microwave drive while probing the readout resonator (Fig. <a data-track=\"click\" data-track-label=\"link\" data-track-action=\"figure anchor\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#Fig1\" rel=\"nofollow noopener\" target=\"_blank\">1e<\/a>). We observe a minimum vortex mode frequency fq\u00a0=\u00a02\u2009GHz at the sweet spot B0\u00a0=\u00a0128\u2009\u03bcT (Fig. <a data-track=\"click\" data-track-label=\"link\" data-track-action=\"figure anchor\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#Fig1\" rel=\"nofollow noopener\" target=\"_blank\">1e<\/a>, inset), with a slope of the hyperbolic field dispersion \u03b3\u00a0=\u00a020\u2009GHz\u2009mT\u22121, reminiscent of a flux qubit<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 27\" title=\"Chiorescu, I., Nakamura, Y., Harmans, C. J. P. M. &amp; Mooij, J. E. Coherent quantum dynamics of a superconducting flux qubit. Science 299, 1869&#x2013;1871 (2003).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR27\" id=\"ref-link-section-d97029111e983\" rel=\"nofollow noopener\" target=\"_blank\">27<\/a>. As the field approaches the sweet spot, the resonance narrows, pointing to magnetic-field fluctuations as dominant noise source<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 28\" title=\"Faoro, L. &amp; Ioffe, L. B. Microscopic origin of low-frequency flux noise in Josephson circuits. Phys. Rev. Lett. 100, 227005 (2008).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR28\" id=\"ref-link-section-d97029111e988\" rel=\"nofollow noopener\" target=\"_blank\">28<\/a>. From measured spectra across 32 field-cooling cycles in six different resonators, we extract values of g, fq, B0 and \u03b3 that are of similar order of magnitude but vary between cycles (Supplementary Information section\u00a0<a data-track=\"click\" data-track-label=\"link\" data-track-action=\"supplementary material anchor\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#MOESM1\" rel=\"nofollow noopener\" target=\"_blank\">II<\/a>), suggesting different underlying vortex configurations. Repeated resonator reflection\u00a0coefficient\u00a0S11\u00a0measurements\u00a0at the sweet spot reveal two distinct clusters in the quadrature plane (Fig. <a data-track=\"click\" data-track-label=\"link\" data-track-action=\"figure anchor\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#Fig2\" rel=\"nofollow noopener\" target=\"_blank\">2a<\/a>), indicating that the vortex state has a lifetime well beyond the 1.2-\u03bcs integration time, thereby enabling single-shot state discrimination. As demonstrated in Fig. <a data-track=\"click\" data-track-label=\"link\" data-track-action=\"figure anchor\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#Fig2\" rel=\"nofollow noopener\" target=\"_blank\">2b<\/a>, by driving at fq, we can calibrate a 20\u2009ns \u03c0-pulse, which inverts its thermal population (see Supplementary Information section\u00a0<a data-track=\"click\" data-track-label=\"link\" data-track-action=\"supplementary material anchor\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#MOESM1\" rel=\"nofollow noopener\" target=\"_blank\">III<\/a> for the Rabi oscillations). These signatures define the VQ states \\(| {\\rm{g}}\\rangle \\) (ground) and \\(| {\\rm{e}}\\rangle \\) (excited). From their steady-state populations, we extract a 74-mK effective temperature. The VQ\u2013resonator interaction induces a state-dependent dispersive shift \\(\\chi \/2{\\rm{\\pi }}={f}_{{\\rm{r}},| {\\rm{e}}\\rangle }-\\,{f}_{{\\rm{r}},| {\\rm{g}}\\rangle }\\). As shown in Fig. <a data-track=\"click\" data-track-label=\"link\" data-track-action=\"figure anchor\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#Fig2\" rel=\"nofollow noopener\" target=\"_blank\">2c<\/a>, fitting the resonator\u2019s phase response to the centres of in-phase and quadrature (IQ) clouds measured versus readout frequency yields \u03c7\/2\u03c0\u00a0=\u00a0\u22121.32\u2009MHz (see Supplementary Information section\u00a0<a data-track=\"click\" data-track-label=\"link\" data-track-action=\"supplementary material anchor\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#MOESM1\" rel=\"nofollow noopener\" target=\"_blank\">IV<\/a> for all measured IQ clouds).<\/p>\n<p><b id=\"Fig2\" class=\"c-article-section__figure-caption\" data-test=\"figure-caption-text\">Fig. 2: The asymmetric quantum Rabi model describes the VQ dispersively coupled to its resonator.<\/b><img decoding=\"async\" aria-describedby=\"figure-2-desc ai-alt-disclaimer-figure-2-1\" src=\"https:\/\/www.europesays.com\/us\/wp-content\/uploads\/2026\/05\/41586_2026_10441_Fig2_HTML.png\" alt=\"Fig. 2: The asymmetric quantum Rabi model describes the VQ dispersively coupled to its resonator.\" loading=\"lazy\" width=\"685\" height=\"610\"\/>The alternative text for this image may have been generated using AI.<\/p>\n<p><b>a<\/b>, Consecutive S11 measurements at the sweet spot show two IQ clouds in the complex plane. The relative occurrence of points in the clouds corresponds to the population of the \\(| {\\rm{g}}\\rangle \\) (ground) and \\(| {\\rm{e}}\\rangle \\) (excited) states. The qubit excited state population Pq yields an effective qubit temperature Teff\u00a0\u2248\u00a074\u2009mK. <b>b<\/b>, Measured IQ clouds following a 20-ns drive at fq calibrated to implement a \u03c0-pulse show a population inversion as expected for a two-level system. The black circles have a radius of 1.5 standard deviation. <b>c<\/b>, Resonator phase response arg(S11), obtained from the centres of the IQ clouds, measured versus readout frequency fRO in the vicinity of fr. A fit to the data (black solid line) yields a dispersive shift of \u03c7\/2\u03c0\u00a0=\u00a0\u22121.32\u2009MHz. The dark red (\\(| {\\rm{g}}\\rangle \\)) and light red (\\(| {\\rm{e}}\\rangle \\)) points correspond to the data in <b>a<\/b> at fRO\u00a0=\u00a07.5714\u2009GHz (dashed line). <b>d<\/b>, Variation of \u03c7 with magnetic field B, shown as triangles, with the yellow triangle corresponding to the measurement in <b>b<\/b>. The dashed line indicates the expected values from the asymmetric quantum Rabi model equation (<a data-track=\"click\" data-track-label=\"link\" data-track-action=\"equation anchor\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#Equ2\" rel=\"nofollow noopener\" target=\"_blank\">2<\/a>) with gAQRM\/2\u03c0\u00a0=\u00a092.5\u2009MHz, and the dash-dotted line to the symmetric quantum Rabi model equation (<a data-track=\"click\" data-track-label=\"link\" data-track-action=\"equation anchor\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#Equ1\" rel=\"nofollow noopener\" target=\"_blank\">1<\/a>) with gSQRM\/2\u03c0\u00a0=\u00a020\u2009MHz. The solid green line represents the qubit frequency (right axis), similar to Fig. <a data-track=\"click\" data-track-label=\"link\" data-track-action=\"figure anchor\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#Fig1\" rel=\"nofollow noopener\" target=\"_blank\">1d<\/a>.<\/p>\n<p>For further insight into the nature of the VQ and its interaction with the grAl resonator, we measure \u03c7 versus field, as shown in Fig. <a data-track=\"click\" data-track-label=\"link\" data-track-action=\"figure anchor\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#Fig2\" rel=\"nofollow noopener\" target=\"_blank\">2d<\/a>. We model it using the quantum Rabi model (QRM) for a spin S\u2009=\u20091\/2 coupled via \\({{\\mathcal{H}}}_{{\\rm{c}}}=\\hbar g({\\hat{a}}^{\\dagger }+\\hat{a}){\\sigma }_{x}\\) to a harmonic oscillator with frequency \u03c9r and Hamiltonian \\({{\\mathcal{H}}}_{{\\rm{r}}}=\\hbar {\\omega }_{{\\rm{r}}}\\left({\\hat{a}}^{\\dagger }\\hat{a}+\\frac{1}{2}\\right)\\) (Supplementary Information section\u00a0<a data-track=\"click\" data-track-label=\"link\" data-track-action=\"supplementary material anchor\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#MOESM1\" rel=\"nofollow noopener\" target=\"_blank\">V<\/a>). Here \\({\\hat{a}}^{\\dagger }\\) and \\(\\hat{a}\\) are the resonator bosonic operators,\u00a0\u0127\u00a0= h\/(2\u03c0) is the reduced\u00a0Planck constant and \u03c3x is the Pauli matrix for a spin <b>S<\/b>\u00a0=\u00a0\u0127\/2<b>\u03c3<\/b>. The interaction energy between the spin and the magnetic field is \\(\\gamma {\\bf{S}}\\cdot (\\widetilde{{\\bf{B}}}+{{\\bf{B}}}^{{\\prime} })\\), where \u03b3 is the gyromagnetic ratio and the field consists of two contributions: a pseudo-field \\(\\widetilde{{\\bf{B}}}\\) that sets the VQ energy at the sweet spot, and the applied magnetic field \\(| {{\\bf{B}}}^{{\\prime} }| =B-{B}_{0}\\) measured from the sweet spot. We compare joint fits of the measured VQ and resonator frequencies in field (Fig. <a data-track=\"click\" data-track-label=\"link\" data-track-action=\"figure anchor\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#Fig1\" rel=\"nofollow noopener\" target=\"_blank\">1d,e<\/a>), using the symmetric quantum Rabi model (SQRM)<\/p>\n<p>$${{\\mathcal{H}}}_{{\\rm{S}}{\\rm{Q}}{\\rm{R}}{\\rm{M}}}={{\\mathcal{H}}}_{{\\rm{r}}}+{{\\mathcal{H}}}_{{\\rm{c}}}+\\frac{\\hbar \\gamma }{2}{{\\sigma }}_{z}\\sqrt{{\\mathop{B}\\limits^{ \\sim }}^{2}+{B}^{{\\prime} 2}},$$<\/p>\n<p>\n                    (1)\n                <\/p>\n<p>and the asymmetric quantum Rabi model (AQRM) <\/p>\n<p>$${{\\mathcal{H}}}_{{\\rm{A}}{\\rm{Q}}{\\rm{R}}{\\rm{M}}}={{\\mathcal{H}}}_{{\\rm{r}}}+{{\\mathcal{H}}}_{{\\rm{c}}}+\\frac{\\hbar \\gamma }{2}{{\\sigma }}_{z}\\mathop{B}\\limits^{ \\sim }-\\frac{\\hbar \\gamma }{2}{{\\sigma }}_{x}{B}^{{\\prime} }\\,.$$<\/p>\n<p>\n                    (2)\n                <\/p>\n<p>Only the AQRM captures the non-monotonic dependence of \u03c7 with B. In contrast, the SQRM predicts a monotonically decreasing \u03c7 with detuning from the resonator. Moreover, using the coupling constant g from the joint fit in Fig. <a data-track=\"click\" data-track-label=\"link\" data-track-action=\"figure anchor\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#Fig1\" rel=\"nofollow noopener\" target=\"_blank\">1d,e<\/a>, we obtain quantitative agreement for the measured \u03c7, as shown in Fig. <a data-track=\"click\" data-track-label=\"link\" data-track-action=\"figure anchor\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#Fig2\" rel=\"nofollow noopener\" target=\"_blank\">2d<\/a>. This suggests that the VQ, possibly consisting of persistent currents, arises from dynamics in a double-well potential, analogous to fluxon tunnelling through the Josephson junction of a flux qubit<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 27\" title=\"Chiorescu, I., Nakamura, Y., Harmans, C. J. P. M. &amp; Mooij, J. E. Coherent quantum dynamics of a superconducting flux qubit. Science 299, 1869&#x2013;1871 (2003).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR27\" id=\"ref-link-section-d97029111e2122\" rel=\"nofollow noopener\" target=\"_blank\">27<\/a>. Within this model, the pseudo-field \\(\\widetilde{B}\\) is given by the fluxon tunnelling amplitude<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 7\" title=\"Matveev, K. A., Larkin, A. I. &amp; Glazman, L. I. Persistent current in superconducting nanorings. Phys. Rev. Lett. 89, 096802 (2002).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR7\" id=\"ref-link-section-d97029111e2143\" rel=\"nofollow noopener\" target=\"_blank\">7<\/a>.<\/p>\n<p>We complete the characterization of the VQ with time-domain measurements at the sweet spot. As shown in Fig. <a data-track=\"click\" data-track-label=\"link\" data-track-action=\"figure anchor\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#Fig3\" rel=\"nofollow noopener\" target=\"_blank\">3a<\/a>, the fitted energy relaxation time is T1\u00a0=\u00a0186\u2009\u03bcs, with values ranging from 40\u2009\u03bcs to 300\u2009\u03bcs across multiple VQ preparation cycles (Supplementary Information section\u00a0<a data-track=\"click\" data-track-label=\"link\" data-track-action=\"supplementary material anchor\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#MOESM1\" rel=\"nofollow noopener\" target=\"_blank\">VI<\/a>). Relaxation times extracted from VQ quantum jumps (Supplementary Information section\u00a0<a data-track=\"click\" data-track-label=\"link\" data-track-action=\"supplementary material anchor\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#MOESM1\" rel=\"nofollow noopener\" target=\"_blank\">VI<\/a>) fall within the temporal fluctuations observed in free decay, indicating a quantum non-demolition readout. Remarkably, the VQ exhibits quantum coherence, with a Ramsey time \\({T}_{2}^{* }=440\\,{\\rm{n}}{\\rm{s}}\\), which extends to \\({T}_{2}^{{\\rm{e}}{\\rm{c}}{\\rm{h}}{\\rm{o}}}=1.2\\,{\\rm{\\mu }}{\\rm{s}}\\) in Hahn-echo measurements, which suppress the low-frequency noise (Fig. <a data-track=\"click\" data-track-label=\"link\" data-track-action=\"figure anchor\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#Fig3\" rel=\"nofollow noopener\" target=\"_blank\">3b,c<\/a>). The Ramsey fringes exhibit a beating pattern, corresponding to a toggling of the VQ\u2019s frequency between two values separated by 1.9\u2009MHz. This feature is sometimes also observed in superconducting qubits<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 29\" title=\"Rieger, D. et al. Granular aluminium nanojunction fluxonium qubit. Nat. Mater. 22, 194&#x2013;199 (2023).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR29\" id=\"ref-link-section-d97029111e2248\" rel=\"nofollow noopener\" target=\"_blank\">29<\/a>, possibly indicative of charge noise or conductance channel fluctuations. The measured VQ lifetime T1 is competitive with superconducting flux qubits<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 30\" title=\"Kjaergaard, M. et al. Superconducting qubits: current state of play. Annu. Rev. Condensed Matter Phys. 11, 369&#x2013;395 (2020).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR30\" id=\"ref-link-section-d97029111e2256\" rel=\"nofollow noopener\" target=\"_blank\">30<\/a>,<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 31\" title=\"Yan, F. et al. The flux qubit revisited to enhance coherence and reproducibility. Nat. Commun. 7, 12964 (2016).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR31\" id=\"ref-link-section-d97029111e2259\" rel=\"nofollow noopener\" target=\"_blank\">31<\/a>, whereas the coherence \\({T}_{2}^{* },{T}_{2}^{\\mathrm{echo}}\\) remains more modest, in line with flux qubit devices realized entirely from disordered superconductors<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 29\" title=\"Rieger, D. et al. Granular aluminium nanojunction fluxonium qubit. Nat. Mater. 22, 194&#x2013;199 (2023).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR29\" id=\"ref-link-section-d97029111e2313\" rel=\"nofollow noopener\" target=\"_blank\">29<\/a>,<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 32\" title=\"Purmessur, C., Chow, K., van Heck, B. &amp; Kou, A. Operation of a high-frequency, phase-slip qubit. Nat. Commun. &#010;                  https:\/\/doi.org\/10.1038\/s41467-025-66348-w&#010;                  &#010;                 (2025).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR32\" id=\"ref-link-section-d97029111e2316\" rel=\"nofollow noopener\" target=\"_blank\">32<\/a>. Away from the sweet spot, both \\({T}_{2}^{* }\\) and \\({T}_{2}^{\\mathrm{echo}}\\) decrease (Supplementary Information section\u00a0<a data-track=\"click\" data-track-label=\"link\" data-track-action=\"supplementary material anchor\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#MOESM1\" rel=\"nofollow noopener\" target=\"_blank\">VI<\/a>), consistent with flux-noise-limited dephasing in loop-based superconducting circuits and motivating a detailed comparison with established flux-noise mechanisms<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 30\" title=\"Kjaergaard, M. et al. Superconducting qubits: current state of play. Annu. Rev. Condensed Matter Phys. 11, 369&#x2013;395 (2020).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR30\" id=\"ref-link-section-d97029111e2379\" rel=\"nofollow noopener\" target=\"_blank\">30<\/a>,<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 31\" title=\"Yan, F. et al. The flux qubit revisited to enhance coherence and reproducibility. Nat. Commun. 7, 12964 (2016).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR31\" id=\"ref-link-section-d97029111e2382\" rel=\"nofollow noopener\" target=\"_blank\">31<\/a>,<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 33\" title=\"G&#xFC;nzler, S. et al. Spin environment of a superconducting qubit in high magnetic fields. Nat. Commun. 16, 1 (2025).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR33\" id=\"ref-link-section-d97029111e2385\" rel=\"nofollow noopener\" target=\"_blank\">33<\/a>. In future experiments, detailed noise characterization<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 31\" title=\"Yan, F. et al. The flux qubit revisited to enhance coherence and reproducibility. Nat. Commun. 7, 12964 (2016).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR31\" id=\"ref-link-section-d97029111e2390\" rel=\"nofollow noopener\" target=\"_blank\">31<\/a>, environment polarizability<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 34\" title=\"Spiecker, M. et al. Two-level system hyperpolarization using a quantum szilard engine. Nat. Phys. 19, 1320&#x2013;1325 (2023).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR34\" id=\"ref-link-section-d97029111e2394\" rel=\"nofollow noopener\" target=\"_blank\">34<\/a>,\u00a0as well as\u00a0susceptibility to in-plane magnetic<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 33\" title=\"G&#xFC;nzler, S. et al. Spin environment of a superconducting qubit in high magnetic fields. Nat. Commun. 16, 1 (2025).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR33\" id=\"ref-link-section-d97029111e2398\" rel=\"nofollow noopener\" target=\"_blank\">33<\/a>\u00a0and electric\u00a0fields<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 35\" title=\"Kristen, M. et al. Giant two-level systems in a granular superconductor. Phys. Rev. Lett. 132, 217002 (2024).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR35\" id=\"ref-link-section-d97029111e2402\" rel=\"nofollow noopener\" target=\"_blank\">35<\/a> could shed light on the microscopic origin of the VQ and its environment.<\/p>\n<p><b id=\"Fig3\" class=\"c-article-section__figure-caption\" data-test=\"figure-caption-text\">Fig. 3: Measurement of low loss and coherence in the VQ.<\/b><img decoding=\"async\" aria-describedby=\"figure-3-desc ai-alt-disclaimer-figure-3-1\" src=\"https:\/\/www.europesays.com\/us\/wp-content\/uploads\/2026\/05\/41586_2026_10441_Fig3_HTML.png\" alt=\"Fig. 3: Measurement of low loss and coherence in the VQ.\" loading=\"lazy\" width=\"685\" height=\"288\"\/>The alternative text for this image may have been generated using AI.<\/p>\n<p><b>a<\/b>, Free energy decay measured after a 20-ns \u03c0-pulse applied selectively to the VQ measured in the ground state \\(| {\\rm{g}}\\rangle \\). The readout pulse has a duration \u03c4m\u00a0=\u00a01.2\u2009\u03bcs. The excited VQ population as a function of wait time t is fitted with an exponential corresponding to T1\u00a0=\u00a0186\u2009\u03bcs (solid line). <b>b<\/b>, Ramsey fringes exhibit a beating pattern, resulting from two frequencies separated by fbeat\u00a0=\u00a01.9\u2009MHz. We extract \\({T}_{2}^{* }\\) Ramsey coherence times of 440\u2009ns. <b>c<\/b>, Spin Hahn-echo measurement with extracted \\({T}_{2}^{{\\rm{e}}{\\rm{c}}{\\rm{h}}{\\rm{o}}}=1.2\\,{\\rm{\\mu }}{\\rm{s}}\\). For each panel, the corresponding pulse sequence is sketched at the top, and the insets show measured coherence times, with error bars indicating the standard deviation from the fit, over several hours.<\/p>\n<p>To give a hypothesis for the origin of the double-well potential of the VQ, we consider the process of introducing vortices into the grAl resonator through field-cooling. Their formation and spatial arrangement depend on the value of the flux bias during cooling \u03d5\u00a0=\u00a0Bcdw2\/\u03a60, where \u03a60\u00a0=\u00a0h\/2e is the magnetic flux quantum, e\u00a0is the charge of an electron, and w is the width of the resonator. In the Pearl limit<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 36\" title=\"Pearl, J. Current distribution in superconducting films carrying quantized fluxoids. Appl. Phys. Lett. 5, 65&#x2013;66 (1964).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR36\" id=\"ref-link-section-d97029111e2579\" rel=\"nofollow noopener\" target=\"_blank\">36<\/a>, where the thickness of the film t \u226a \u03bbL, the threshold for stable vortices is \\({\\phi }_{{\\rm{S}}}=(2\/{\\rm{\\pi }})\\mathrm{ln}(2w\/{\\rm{\\pi }}\\xi )\\) (refs. <a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" title=\"Kogan, V. G. Pearl&#x2019;s vortex near the film edge. Phys. Rev. B 49, 15874 (1994).\" href=\"#ref-CR37\" id=\"ref-link-section-d97029111e2649\">37<\/a>,<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" title=\"Stan, G., Field, S. B. &amp; Martinis, J. M. Critical field for complete vortex expulsion from narrow superconducting strips. Phys. Rev. Lett. 92, 097003 (2004).\" href=\"#ref-CR38\" id=\"ref-link-section-d97029111e2649_1\">38<\/a>,<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 39\" title=\"Bronson, E., Gelfand, M. P. &amp; Field, S. B. Equilibrium configurations of pearl vortices in narrow strips. Phys. Rev. B 73, 144501 (2006).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR39\" id=\"ref-link-section-d97029111e2652\" rel=\"nofollow noopener\" target=\"_blank\">39<\/a>), corresponding to \u03d5S\u00a0=\u00a03.59 for our geometry (Supplementary Information section\u00a0<a data-track=\"click\" data-track-label=\"link\" data-track-action=\"supplementary material anchor\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#MOESM1\" rel=\"nofollow noopener\" target=\"_blank\">VII<\/a>). The Gibbs energy for vortices threading the film<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 40\" title=\"Bai, R. et al. Flux trapping in NbTiN strips and structures. Preprint at &#010;                  https:\/\/arxiv.org\/abs\/2503.14457&#010;                  &#010;                 (2025).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR40\" id=\"ref-link-section-d97029111e2664\" rel=\"nofollow noopener\" target=\"_blank\">40<\/a>,<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 41\" title=\"Kuit, K. H. et al. Vortex trapping and expulsion in thin-film YBa2Cu3O7&#x2212;&#x3B4; strips. Phys. Rev. B 77, 134504 (2008).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR41\" id=\"ref-link-section-d97029111e2667\" rel=\"nofollow noopener\" target=\"_blank\">41<\/a> is <\/p>\n<p>$${G}_{1}(x)={\\varepsilon }_{0}\\mathrm{ln}\\left(\\frac{2w}{{\\rm{\\pi }}\\xi }\\sin \\left(\\frac{{\\rm{\\pi }}x}{w}\\right)+1\\right)-\\frac{{\\varPhi }_{0}(B-n{\\varPhi }_{0})}{{\\mu }_{0}\\varLambda }x(w-x),$$<\/p>\n<p>\n                    (3)\n                <\/p>\n<p>where \\({\\varepsilon }_{0}={\\varPhi }_{0}^{2}\/(2{\\rm{\\pi }}{\\mu }_{0}\\varLambda )\\) sets the single-vortex energy scale, n is the density of vortices (n\u00a0=\u00a00 for the first vortex), \\(\\varLambda =2{\\lambda }_{{\\rm{L}}}^{2}\/t\\) is the Pearl length of the resonator, and x is the position of the vortex measured from the resonator edge. As B decreases from BS\u00a0=\u00a0\u03d5S\u03a60\/w2 to zero, the minimum of G1(x) vanishes (Fig. <a data-track=\"click\" data-track-label=\"link\" data-track-action=\"figure anchor\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#Fig4\" rel=\"nofollow noopener\" target=\"_blank\">4<\/a>, baseline), and in the absence of pinning the vortex would be expelled.<\/p>\n<p><b id=\"Fig4\" class=\"c-article-section__figure-caption\" data-test=\"figure-caption-text\">Fig. 4: Origin of the double-well potential.<\/b><img decoding=\"async\" aria-describedby=\"figure-4-desc ai-alt-disclaimer-figure-4-1\" src=\"https:\/\/www.europesays.com\/us\/wp-content\/uploads\/2026\/05\/41586_2026_10441_Fig4_HTML.png\" alt=\"Fig. 4: Origin of the double-well potential.\" loading=\"lazy\" width=\"685\" height=\"524\"\/>The alternative text for this image may have been generated using AI.<\/p>\n<p>Gibbs free energy G1 (equation (<a data-track=\"click\" data-track-label=\"link\" data-track-action=\"equation anchor\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#Equ3\" rel=\"nofollow noopener\" target=\"_blank\">3<\/a>), baseline) of a single vortex, shown with added pinning potentials modelled as Lorentzian dips, in units of \\({\\varepsilon }_{0}={\\varPhi }_{0}^{2}\/2{\\rm{\\pi }}{\\mu }_{0}\\varLambda \\approx \\text{2}\\,\\mathrm{THz}\\). The vortex position is measured from the edge, as indicated by the coordinate axis. Colours represent different applied magnetic fields from BS\u00a0=\u00a0\u03d5S\u03a60\/w2 to \u2212B0. Top inset: example of a double-well potential formed by the energy landscape of adjacent pinning sites separated by \u03b4LR and offset in energy by \u03f5. The localized wavefunctions correspond to the two vortex positions \\(| {\\rm{L}}\\rangle \\) and \\(| {\\rm{R}}\\rangle \\), coupled by tunnelling amplitude \u0394, with an energy splitting of \u0127\u03c9q. Bottom inset: at the sweet spot (B0, which can be higher or lower than BS; see Supplementary Information section\u00a0<a data-track=\"click\" data-track-label=\"link\" data-track-action=\"supplementary material anchor\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#MOESM1\" rel=\"nofollow noopener\" target=\"_blank\">II<\/a>), the double well is degenerate, with VQ states forming symmetric and antisymmetric combinations of the localized wavefunctions, yielding \u0127\u03c9q\u00a0=\u00a02\u0394.<\/p>\n<p>To account for the measured stability of the VQ across magnetic-field sweeps (Fig. <a data-track=\"click\" data-track-label=\"link\" data-track-action=\"figure anchor\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#Fig1\" rel=\"nofollow noopener\" target=\"_blank\">1<\/a>), we incorporate pinning potentials, presumably abundant given the disordered nature of grAl. They are modelled by adding Lorentzian dips \\({V}_{{\\rm{p}}{\\rm{i}}{\\rm{n}}}={V}_{i}{(1+{(x-{x}_{i})}^{2}\/{\\sigma }_{i}^{2})}^{-1}\\) to G1(x), at random positions xi, depth Vi and width \u03c3i, sketched as the coloured energy landscapes in Fig. <a data-track=\"click\" data-track-label=\"link\" data-track-action=\"figure anchor\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#Fig4\" rel=\"nofollow noopener\" target=\"_blank\">4<\/a>. A vortex tunnelling between pinning sites forms a double-well potential (Fig. <a data-track=\"click\" data-track-label=\"link\" data-track-action=\"figure anchor\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#Fig4\" rel=\"nofollow noopener\" target=\"_blank\">4<\/a>, top inset), in which B tunes the relative pinning depths according to equation (<a data-track=\"click\" data-track-label=\"link\" data-track-action=\"equation anchor\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#Equ3\" rel=\"nofollow noopener\" target=\"_blank\">3<\/a>). At B0, the minima are degenerate and the vortex delocalizes, with \\(| {\\rm{g}}\\rangle \\) and \\(| {\\rm{e}}\\rangle \\) given by symmetric and antisymmetric superpositions of \\(| {\\rm{L}}\\rangle \\) and \\(| {\\rm{R}}\\rangle \\) wavefunctions (Fig. <a data-track=\"click\" data-track-label=\"link\" data-track-action=\"figure anchor\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#Fig4\" rel=\"nofollow noopener\" target=\"_blank\">4<\/a>, bottom inset).<\/p>\n<p>This hypothesis is supported by the fact that typically measured gyromagnetic ratios \u03b3\/2\u03c0\u2009=\u20093\u201325\u2009GHz\u2009mT\u22121 are consistent with flux tunnelling between pinning sites separated by tens of nanometres (Supplementary Information section\u00a0<a data-track=\"click\" data-track-label=\"link\" data-track-action=\"supplementary material anchor\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#MOESM1\" rel=\"nofollow noopener\" target=\"_blank\">VII<\/a>), reminiscent of tunnelling through grAl nanojunctions<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 29\" title=\"Rieger, D. et al. Granular aluminium nanojunction fluxonium qubit. Nat. Mater. 22, 194&#x2013;199 (2023).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR29\" id=\"ref-link-section-d97029111e3378\" rel=\"nofollow noopener\" target=\"_blank\">29<\/a>. Moreover, to leading order, a kinetic-inductance-mediated VQ\u2013resonator coupling g\/\u03c9r\u00a0\u2248\u20090.1\u20131% (Supplementary Information section\u00a0<a data-track=\"click\" data-track-label=\"link\" data-track-action=\"supplementary material anchor\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#MOESM1\" rel=\"nofollow noopener\" target=\"_blank\">VIII<\/a>) is consistent with the observed avoided level crossings. Although single-vortex pinning can account for the observed VQ, it is well established that multiple vortices simultaneously enter the resonator once the threshold for entry is reached<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 39\" title=\"Bronson, E., Gelfand, M. P. &amp; Field, S. B. Equilibrium configurations of pearl vortices in narrow strips. Phys. Rev. B 73, 144501 (2006).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR39\" id=\"ref-link-section-d97029111e3393\" rel=\"nofollow noopener\" target=\"_blank\">39<\/a>, as illustrated by the set of Gibbs curves in the foreground of Fig. <a data-track=\"click\" data-track-label=\"link\" data-track-action=\"figure anchor\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#Fig4\" rel=\"nofollow noopener\" target=\"_blank\">4<\/a>. We estimate the VQ\u2013VQ interaction in the 10\u2013100\u2009MHz range (Supplementary Information section\u00a0<a data-track=\"click\" data-track-label=\"link\" data-track-action=\"supplementary material anchor\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#MOESM1\" rel=\"nofollow noopener\" target=\"_blank\">IX<\/a>), suggesting that collective vortex dynamics is unlikely. Nevertheless, distinguishing between single- and multi-vortex dynamics, for instance, using imaging methods<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 40\" title=\"Bai, R. et al. Flux trapping in NbTiN strips and structures. Preprint at &#010;                  https:\/\/arxiv.org\/abs\/2503.14457&#010;                  &#010;                 (2025).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR40\" id=\"ref-link-section-d97029111e3404\" rel=\"nofollow noopener\" target=\"_blank\">40<\/a>,<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" title=\"Kirtley, J. R. Fundamental studies of superconductors using scanning magnetic imaging. Rep. Prog. Phys. 73, 126501 (2010).\" href=\"#ref-CR42\" id=\"ref-link-section-d97029111e3407\">42<\/a>,<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" title=\"Suderow, H., Guillamon, I., Rodrigo, J. G. &amp; Vieira, S. Imaging superconducting vortex core and lattice with the scanning tunneling microscope. Supercond. Sci. Technol. 27, 063001 (2014).\" href=\"#ref-CR43\" id=\"ref-link-section-d97029111e3407_1\">43<\/a>,<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" title=\"Persky, E., Sochnikov, I. &amp; Kalisky, B. Studying quantum materials with scanning SQUID microscopy. Annu. Rev. Condens. Matter Phys. 13, 385&#x2013;405 (2022).\" href=\"#ref-CR44\" id=\"ref-link-section-d97029111e3407_2\">44<\/a>,<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 45\" title=\"Weber, T. et al. Advanced SQUID-on-lever scanning probe for high-sensitivity magnetic microscopy with sub-100-nm spatial resolution. Phys. Rev. Appl. 24, 054041 (2025).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR45\" id=\"ref-link-section-d97029111e3410\" rel=\"nofollow noopener\" target=\"_blank\">45<\/a>, or by shaping the resonator width<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 18\" title=\"Nsanzineza, I. &amp; Plourde, B. Trapping a single vortex and reducing quasiparticles in a superconducting resonator. Phys. Rev. Lett. &#010;                  https:\/\/doi.org\/10.1103\/physrevlett.113.117002&#010;                  &#010;                 (2014).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR18\" id=\"ref-link-section-d97029111e3414\" rel=\"nofollow noopener\" target=\"_blank\">18<\/a>, remains an important avenue for future research.<\/p>\n<p>In conclusion, field-cooling a grAl micro-stripline resonator reproducibly generates VQ states that couple dispersively to the resonator and can be coherently driven. Our results demonstrate that superconducting vortices can harbour quantum coherence on microsecond timescales. Remarkably, the VQ energy relaxation times are on the order of hundreds of microseconds, comparable to those of engineered superconducting qubits<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 11\" title=\"Blais, A., Grimsmo, A. L., Girvin, S. M. &amp; Wallraff, A. Circuit quantum electrodynamics. Rev. Mod. Phys. 93, 025005 (2021).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR11\" id=\"ref-link-section-d97029111e3422\" rel=\"nofollow noopener\" target=\"_blank\">11<\/a>,<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 30\" title=\"Kjaergaard, M. et al. Superconducting qubits: current state of play. Annu. Rev. Condensed Matter Phys. 11, 369&#x2013;395 (2020).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR30\" id=\"ref-link-section-d97029111e3425\" rel=\"nofollow noopener\" target=\"_blank\">30<\/a>, and qualitatively distinct from the dissipation expected for Abrikosov vortex dynamics. This supports a picture of grAl as a three-dimensional network of Josephson junctions, expected to host gapful-core vortices once the coherence length \u03be becomes comparable to the intergrain spacing \u2113, with a growing minigap for \u03be \u2272 \u2113 (refs. <a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 2\" title=\"Bouadim, K., Loh, Y. L., Randeria, M. &amp; Trivedi, N. Single- and two-particle energy gaps across the disorder-driven superconductor&#x2013;insulator transition. Nat. Phys. 7, 884&#x2013;889 (2011).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR2\" id=\"ref-link-section-d97029111e3442\" rel=\"nofollow noopener\" target=\"_blank\">2<\/a>,<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 3\" title=\"Kiselov, D., Skvortsov, M. A. &amp; Feigel&#x2019;man, M. V. Gapful electrons in a vortex core in granular superconductors. SciPost Phys. &#010;                  https:\/\/doi.org\/10.21468\/scipostphys.15.1.008&#010;                  &#010;                 (2023).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR3\" id=\"ref-link-section-d97029111e3445\" rel=\"nofollow noopener\" target=\"_blank\">3<\/a>). The observed dispersive shifts and spectra are accurately captured by an asymmetric quantum Rabi model, consistent with a two-level system in a double-well potential. Microscopically, this may arise from vortex tunnelling between pinning sites, modulated by the magnetic-field dependence of the Gibbs energy. This hypothesis, although consistent with our measurements, remains to be confirmed by future experiments such as scanning tunnelling or scanning superconducting quantum interference device\u00a0(SQUID) microscopy.<\/p>\n<p>Looking ahead, the measurement of quantum coherence in vortex states, along with their relative technological simplicity, opens several exciting avenues in quantum science. Disordered superconductors beyond grAl<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 46\" title=\"Weitzel, A. et al. Sharpness of the Berezinskii&#x2013;Kosterlitz&#x2013;Thouless transition in disordered NbN films. Phys. Rev. Lett. 131, 186002 (2023).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR46\" id=\"ref-link-section-d97029111e3452\" rel=\"nofollow noopener\" target=\"_blank\">46<\/a>,<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 47\" title=\"Charpentier, T. et al. First-order quantum breakdown of superconductivity in an amorphous superconductor. Nat. Phys. 21, 104&#x2013;109 (2025).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR47\" id=\"ref-link-section-d97029111e3455\" rel=\"nofollow noopener\" target=\"_blank\">47<\/a> or engineered two-dimensional networks of Josephson junctions<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 48\" title=\"B&#xF8;ttcher, C. G. L., Nichele, F., Shabani, J., Palmstr&#xF8;m, C. J. &amp; Marcus, C. M. Dynamical vortex transitions in a gate-tunable two-dimensional Josephson junction array. Phys. Rev. B 108, 134517 (2023).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR48\" id=\"ref-link-section-d97029111e3459\" rel=\"nofollow noopener\" target=\"_blank\">48<\/a> may host similar VQs, shedding light onto the complex physics in the vicinity of the superconductor-to-insulator transition<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 49\" title=\"Haviland, D. B., Liu, Y. &amp; Goldman, A. M. Onset of superconductivity in the two-dimensional limit. Phys. Rev. Lett. 62, 2180 (1989).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR49\" id=\"ref-link-section-d97029111e3463\" rel=\"nofollow noopener\" target=\"_blank\">49<\/a>,<a data-track=\"click\" data-track-action=\"reference anchor\" data-track-label=\"link\" data-test=\"citation-ref\" aria-label=\"Reference 50\" title=\"Glezer Moshe, A., Tuvia, G., Avraham, S., Farber, E. &amp; Deutscher, G. Tunneling study in granular aluminum near the Mott metal-to-insulator transition. Phys. Rev. B 104, 054508 (2021).\" href=\"http:\/\/www.nature.com\/articles\/s41586-026-10441-7#ref-CR50\" id=\"ref-link-section-d97029111e3466\" rel=\"nofollow noopener\" target=\"_blank\">50<\/a>. Moreover, this would offer an embedded tool for material characterization at the microscopic level. In the same spirit, if the observed dynamics indeed stem from single-vortex tunnelling, VQs could be harnessed for nanoscale sensing. Ultimately, engineering the pinning landscape and device geometry, combined with noise spectroscopy and susceptibility measurements to magnetic and electric fields, will be crucial to enhance VQ coherence and possibly launch a vortex-based quantum information platform.<\/p>\n","protected":false},"excerpt":{"rendered":"From the moment of its discovery, the antagonistic relation between superconductivity and a magnetic field has provided a&hellip;\n","protected":false},"author":3,"featured_media":778848,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[25],"tags":[10046,2262,10047,492,13632,2913,159,27105,27577,67,132,68],"class_list":{"0":"post-778847","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-physics","8":"tag-humanities-and-social-sciences","9":"tag-magnetic-properties-and-materials","10":"tag-multidisciplinary","11":"tag-physics","12":"tag-quantum-information","13":"tag-qubits","14":"tag-science","15":"tag-single-photons-and-quantum-effects","16":"tag-superconducting-properties-and-materials","17":"tag-united-states","18":"tag-unitedstates","19":"tag-us"},"share_on_mastodon":{"url":"https:\/\/pubeurope.com\/@us\/116531469596946470","error":""},"_links":{"self":[{"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/posts\/778847","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/comments?post=778847"}],"version-history":[{"count":0,"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/posts\/778847\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/media\/778848"}],"wp:attachment":[{"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/media?parent=778847"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/categories?post=778847"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/tags?post=778847"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}