Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session C04: Coherent Magnonics: Progress to the Quantum RegimeInvited
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Sponsoring Units: DCMP DMP GMAG Chair: David Awschalom, University of Chicago Room: LACC 151 |
Monday, March 5, 2018 2:30PM - 3:06PM |
C04.00001: Sensing magnetization oscillation in quantum regime Invited Speaker: Yutaka Tabuchi Quanta of magnetization oscillations, i.e., magnons, are essential ingredients in spintronics technology. Although their characteristics have been investigated for a long time, the behavior in the quantum regime, where the number of thermal excited magnons is nearly zero, is still unknown. Here we demonstrate ultra-sensitive sensing of magnons using a superconducting qubit. Transmon-type qubits, which are formed by two electrodes shunted by Josephson junctions, have dipole antennas in their structures and thus they couple to surrounding electromagnetic fields. Owing to their huge dipole moments, the qubits can detect a change in microwave signal to a single photon level. We exploit such feature for sensing the magnetization oscillation in a magnet. We use a microwave cavity to induce an effective coupling between them; both the qubit and the magnetization couple with the same microwave field mode but through different components [1]. With an appropriate frequency detuning between the qubit and a magnetization oscillation mode, the qubit frequency shifts depending on the number of magnons in the oscillation mode. The peak shift is discretized in the limit where the qubit linewidth is narrower than the shift for a single magnon, so that we can count magnons in the oscillation mode to a single magnon level. We experimentally show that the coherently excited magnetization oscillation obeys the Poissonian magnon number distribution [2]. Our ultra-sensitive sensing method provides a powerful tool for magnetization oscillation sensing as well as quantum information processing. |
Monday, March 5, 2018 3:06PM - 3:42PM |
C04.00002: Long-range spin wave control of spin qubits in nanodiamonds1 Invited Speaker: Paolo Andrich A growing interest in the investigation and control of spin systems at the nanoscale level has emerged in recent years, spurred by advancements in the manipulation and harnessing of the spin degree of freedom, and by the potential to impact the fields of quantum information processing, sensing, and energy efficiency. Particularly intriguing is the possibility of combining different spin-based materials and devices to take advantage of their unique characteristics within a hybrid architecture. Here, we explore the interplay between ferromagnetic systems and spin qubits in diamond nanoparticles, both to investigate the viability of spin wave/qubit control and to advance the understanding of fundamental spintronics effects. In particular, we investigate a regime in which surface spin waves excited in a ferromagnetic layer coherently interact with the qubits, allowing for their efficient and uniform control over a spatial range of hundreds of microns.2 The results have important implications for engineering strongly coupled hybrid quantum spin systems, as well as for the fields of nanoscale magnetic and thermal sensing. |
Monday, March 5, 2018 3:42PM - 4:18PM |
C04.00003: Cavity Elecctrodynamics of Magnons Invited Speaker: Hong Tang Hybrid magnonic systems have emerged recently as an important approach for coherent information processing. The great tunability and long lifetime make magnon an ideal information carriers. We demonstrate, that particularly in magnetic insulator yttrium iron garnet (YIG), the coupling between magnon and microwave photons can reach the strong and even ultrastrong coupling regime thanks to the large spin density in YIG. Moreover, since YIG possesses excellent mechanical and optical properties, we show that by leveraging strongly coupled cavity magnonics system, coherent coupling between magnon and phonon, between magnon and optical photons can be all realized. Our work firmly establishes the great potential of magnons as an information transducer that can support coherent information inter-conversion of information carrier among different physics domains. |
Monday, March 5, 2018 4:18PM - 4:54PM |
C04.00004: Designing magnonic crystals for quantum control Invited Speaker: Michael Flatté Ferromagnetic materials provide excellent opportunites for strong hybridization between microwave photons and spin excitations, as the collective motion of exchange-locked spins enhances light-matter coupling[1,2]. Quantum control of this coupling is eased through the ability to electrically manipulate the energy of spin excitations, bringing them into and out of resonance with microwave photons. Electric fields applied to insulating magnets can efficiently change spin excitation energies, without the dissipation produced with electrical current-induced manipulation. The Dzyaloshinskii-Moriya interaction provides an approach to manipulate spin excitations with electric fields, and has been demonstrated in yttrium iron garnet. The small effect seen in bulk magnets, well described by theoretical calculations[3], can be dramatically enhanced by patterning the ferromagnetic insulating material into one-dimensional and two-dimensional magnonic crystals. It is then possible to shift the magnonic gaps into and out of resonance with a microwave cavity using an electric field, paving the way for a fully quantum switch that works via voltages, not currents, and has nearly no dissipation. This will benefit coherent quantum transduction between electric, magnetic, and electromagnetic degrees of freedom in a quantum device. |
Monday, March 5, 2018 4:54PM - 5:30PM |
C04.00005: High-Q spin wave excitations in the organic-based ferrimagnet vanadium tetracyanoethylene Invited Speaker: Ezekiel Johnston-Halperin The development of quantum magnonics relies implicitly on the ability to excite and exploit long lived spin wave excitations in a magnetic material. That requirement has led to the nearly universal reliance on yittrium iron garnet (YIG), which for half a century has reigned as the unchallenged leader in high-Q, low loss magnetic resonance and spin wave excitation despite extensive efforts to identify alternative materials. Surprisingly, the organic-based ferrimagnet vanadium tetracyanoethylene (V[TCNE]2) has recently emerged as a compelling alternative to YIG. In contrast to other organic-based materials V[TCNE]2 exhibits a Curie temperature of over 600 K with robust room temperature hysteresis with sharp switching to full saturation. Further, since V[TCNE]2 is grown via chemical vapor deposition (CVD) at 50 C it can be conformally deposited as a thin film on a wide variety of substrates. Our recent work has exploited this potential to construct a microwave waveguide in which V[TCNE]2 is deposited as a bridge across two coplanar waveguides, exhibiting standing wave spin-wave resonances with Q of over 3,200 under ambient conditions. This Q rivals the very best thin-film YIG devices, which must be grown epitaxially on GGG substrates at temperatures over 800 C. Work in preparation shows that this Q can be further enhanced by moving to the thick film geometry, which is well known to reduce surface scattering, yielding Qs that are competitive with polished YIG spheres. When added to the ease of patterning and integration afforded by the low temperature CVD deposition process, these results clearly demonstrate the potential for V[TCNE]2 to play a major role in the development of long-lived coherent spin wave excitations in quantum magnonic devices. |
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