\n\t\t\t\t\t\t\t\t\t\tBYLINE: Joseph E. Harmon\t\t\t\t\t\t\t\t\t\t<\/p>\n
The future of computing lies in the surprising world of quantum physics, where the rules are much different from the ones that power today\u2019s devices.\u00a0Quantum<\/a>\u00a0computers promise to tackle problems too complex for even the fastest\u00a0supercomputers<\/a>\u00a0running on silicon chips. To make this vision real, scientists around the world are searching for new quantum materials with unusual, almost otherworldly properties.\u00a0<\/p>\n One of the more intriguing candidates is called a quantum spin liquid \u2014 a state of matter where electron spins never settle down, even at the coldest temperatures in the universe. To date, however, preparing such a quantum state in a lab has proven stubbornly elusive. In a collaborative project with multiple institutions, scientists at the U.S. Department of Energy\u2019s (DOE) Argonne National Laboratory now report coming tantalizingly closer.\u00a0<\/p>\n As explained by Argonne Senior Physicist and Group Leader Daniel Haskel, in these materials, it\u2019s not atoms that stay fluid as in an ordinary liquid, but the tiny magnetic orientations \u2014 or spins \u2014 of electrons. Each spin wants to\u00a0\u200b\u201cget along\u201d with its neighbors by aligning in a way that keeps everyone content. But when the spins are pushed closer together under pressure, satisfying every neighbor becomes impossible. The result is a kind of magnetic deadlock \u2014 called frustration \u2014 in which the spins can no longer settle into any fixed arrangement. The result is a continuous, entangled dance of fluctuating spins, even when cooled to near absolute zero.\u00a0<\/p>\n \u201cAchieving this quantum spin state would be a major milestone,\u201d said Eduardo Poldi, a graduate student at the University of Illinois Chicago in Professor Russell Hemley\u2019s group, with a joint appointment at Argonne.\u00a0\u200b\u201cSome types of quantum spin liquids could serve as a new platform for qubits, the basic building blocks of a quantum computer.\u201d<\/p>\n In their latest experiment at Argonne\u2019s Advanced Photon Source (APS), a\u00a0DOE\u00a0Office of Science user facility, the team turned their attention to a crystalline material thought to possibly have the ingredients for a spin liquid. It is an oxide containing sodium, cobalt and antimony (NCSO).\u00a0<\/p>\n The material has special characteristics: Its cobalt atoms form a honeycomb pattern, like a beehive. That structure plays a key role. The electron spins tend to align perpendicular to the edges of each cell in the honeycomb, but at points where three edges meet, not all spins can align to satisfy their neighbors \u2014 creating a state of frustration (see image). Theoretical models predict that this frustration can host a quantum spin liquid with topological protection. In such a state, excitations can form that encode quantum information yet remain resistant to outside disturbance. That built-in protection could help protect fragile quantum states \u2014 an essential step toward stable quantum technologies.<\/p>\n In\u00a0earlier work<\/a>, Argonne researchers found that extreme pressure can serve as a control knob to induce quantum spin behavior. Using two flat diamonds to squeeze the electrons together in a magnetic crystal, they suppressed a material\u2019s usual magnetic order and nudged it toward a spin liquid state.<\/p>\n \u201cPressure provides a way to reduce the separation between atoms and their electrons,\u201d said\u00a0APS\u00a0Physicist Gilberto Fabbris.\u00a0\u200b\u201cBy adjusting that distance, we can drive a magnetic crystal into a frustrated state. At a certain extreme pressure, magnetism disappears \u2014 and a spin liquid emerges.\u201d<\/p>\n Achieving that state, however, is extraordinarily difficult. The pressure must be high enough to suppress magnetic order yet applied in a way that does not damage the crystal\u2019s internal symmetry. Using specialized diamond anvil cells at\u00a0APS, the researchers were able to compress the\u00a0NCSO\u00a0to over 1 million atmospheres \u2014 roughly 1,000 times the pressure at the bottom of the ocean \u2014 all within a region smaller than the width of a human hair.\u00a0<\/p>\n The team used three\u00a0APS\u00a0beamlines<\/a>\u00a0to analyze their\u00a0NCSO\u00a0sample from room temperature down to around absolute zero and from one to 1 million atmospheres. In particular, they performed X-ray diffraction and emission spectroscopy at beamlines\u00a016-BM-D\u00a0and\u00a016-ID-D\u00a0to unravel the atomic structure and electron spins of the\u00a0NCSO\u00a0over the wide range of temperature and pressure. They also used beamline\u00a04-ID-D\u00a0to track the changing magnetic properties.\u00a0<\/p>\n Especially important, Poldi noted, was the ability at\u00a0APS\u00a0to measure the spin state within an atom and the spin-spin correlations between atoms under extreme pressures. The\u00a0APS\u00a0is the only facility in the United States where such an experiment is possible.<\/p>\n \u201cAchieving this quantum spin state would be a major milestone. Some types of quantum spin liquids could serve as a new kind of qubit, the basic building block of a quantum computer.\u201d\u00a0\u2014 Eduardo Poldi, graduate student at the University of Illinois Chicago with a joint appointment at Argonne.<\/p>\n The results indicate that the\u00a0NCSO\u00a0shows clear signs of approaching a spin liquid state, although the nature of the frustrated quantum state differs from the one predicted by theory. That makes it a promising material for future studies \u2014 and possibly, a stepping stone toward other honeycomb-structured materials that exhibit the strange properties of quantum materials. With the recent upgrade to the\u00a0APS, researchers will be able to investigate candidate materials at five times higher pressures.<\/p>\n \u201cQuantum spin liquids\u00a0with topological\u00a0protection provide an\u00a0exciting path\u00a0toward building qubits\u00a0that are naturally shielded from outside interference,\u201d Haskel said. What began as a fundamental physics experiment may now point toward a new route for building more stable and fault-tolerant quantum technologies.\u00a0<\/p>\n Participating institutions in this research include Argonne, University of Illinois Chicago, Universidade Estadual de Campinas in Brazil, Northern Illinois University, University of Alabama at Birmingham and DOE\u2019s Oak Ridge National Laboratory.\u00a0<\/p>\n The research first appeared in\u00a0Communications Physics<\/a>. In addition to Daniel Haskel, Eduardo Poldi and Gilberto Fabbris, contributing authors from Argonne include Rodolfo Tartaglia, Hyowon Park, Michel Antonius Van Veenendaal, Jong Woo Kim, Hong Zheng, and John Mitchell.<\/p>\n The research received funding from the\u00a0DOE\u00a0Office of Basic Energy Sciences, National Science Foundation and the National Nuclear Security Administration.<\/p>\n About the\u00a0Advanced Photon Source<\/p>\n The U. S. Department of Energy Office of Science\u2019s Advanced Photon Source (APS) at Argonne National Laboratory is one of the world\u2019s most productive X-ray light source facilities. The\u00a0APS\u00a0provides high-brightness X-ray beams to a diverse community of researchers in materials science, chemistry, condensed matter physics, the life and environmental sciences, and applied research. These X-rays are ideally suited for explorations of materials and biological structures; elemental distribution; chemical, magnetic, electronic states; and a wide range of technologically important engineering systems from batteries<\/a> to fuel injector sprays, all of which are the foundations of our nation\u2019s economic, technological, and physical well-being. Each year, more than 5,000 researchers use the\u00a0APS\u00a0to produce over 2,000 publications detailing impactful discoveries, and solve more vital biological protein structures than users of any other X-ray light source research facility.\u00a0APS\u00a0scientists and engineers innovate technology that is at the heart of advancing accelerator and light-source operations. This includes the insertion devices that produce extreme-brightness X-rays prized by researchers, lenses that focus the X-rays down to a few nanometers, instrumentation that maximizes the way the X-rays interact with samples being studied, and software that gathers and manages the massive quantity of data resulting from discovery research at the\u00a0APS.<\/p>\n This research used resources of the Advanced Photon Source, a U.S.\u00a0DOE\u00a0Office of Science User Facility operated for the\u00a0DOE\u00a0Office of Science by Argonne National Laboratory under Contract No.\u00a0DE-AC02-06CH11357.<\/p>\n Argonne National Laboratory<\/a>\u00a0seeks solutions to pressing national problems in science and technology by conducting leading-edge basic and applied research in virtually every scientific discipline. Argonne is managed by\u00a0UChicago Argonne,\u00a0LLC<\/a>\u00a0for the\u00a0U.S. Department of Energy\u2019s Office of Science.<\/a><\/p>\n The U.S. Department of Energy\u2019s Office of Science\u00a0is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, visit\u00a0https:\/\/\u200bener\u200bgy\u200b.gov\/\u200bs\u200bc\u200bience<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"BYLINE: Joseph E. 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