Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session V29: Hybrid Systems: Coupling to Ensembles and Single Electrons in HeliumFocus
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Sponsoring Units: DQI Chair: Charlotte Boettcher Room: BCEC 162A |
Thursday, March 7, 2019 2:30PM - 2:42PM |
V29.00001: Broadband electron spin resonance spectroscopy with a superconducting resonator, Part 1 : Theory Jerome Bourassa, Gregory Brookes, Dany Lachance-Quirion, David Roy-Guay, Raphaël Lafond-Mercier, Léo Desormiers, Vincent Bonneau, Michel Pioro-Ladriere Electron spin resonance (ESR) spectroscopy is a useful tool for characterizing spin defects relevant to quantum technologies. Typical ESR systems are based on a resonant exchange interaction between the spins and a high-Q resonant cavity or resonator. While sensitive, the small magnetic-dipole coupling strength limits the ESR detection bandwidth in the dispersive regime and alternative coupling strategies must be used. One such strategy is to rely instead on a longitudinal interaction where the spin magnetization directly influences the resonator frequency, irrespective of the spin transition frequency. |
Thursday, March 7, 2019 2:42PM - 2:54PM |
V29.00002: Broadband electron spin resonance spectroscopy with a superconducting resonator, Part 2 : Experiments Gregory Brookes, Dany Lachance-Quirion, David Roy-Guay, Raphaël Lafond-Mercier, Jerome Bourassa, Michel Pioro-Ladriere Electron spin resonance (ESR) spectroscopy is a useful characterization tool for quantum materials that is traditionally limited in terms of sensitivity, probing frequency, and volume. Here, we present an alternative: a longitudinal spin-cavity coupling mechanism based on the effects of the spin polarization on high-kinetic-inductance superconducting resonators. This interaction allows for broadband measurements to probe spin transitions. |
Thursday, March 7, 2019 2:54PM - 3:06PM |
V29.00003: Effecting spontaneous coherence in hybridised cavity-spin ensemble systems with incoherent driving Rhonda Au Yeung, Marzena Hanna Szymanska, Eran Ginossar When the fermionic levels of spin-1/2 atoms are dipole-coupled to cavity photons which decay into the environment, energy losses are normally compensated by laser pumping. This work explores the consequence of weakening and removing the laser pump mechanism. We use Keldysh field theory [1] to study spontaneous coherence in a Tavis-Cummings system [2] (in the spirit of Bose-Einstein condensates) following incoherent driving from the decay bath. This novel approach presents opportunities to search for exotic nonequilibrium phase transitions, as well as building hybrid quantum structures using a superconducting resonator coupled strongly to crystalline impurity spin centres in diamond [3] to study quantum simulation. Our approach includes both coherent and incoherent photon dynamics from the decay bath. The Keldysh action would contain additional terms in the Dyson equation where only coherent photons are considered, and their effects would be seen in resulting phase diagrams. |
Thursday, March 7, 2019 3:06PM - 3:42PM |
V29.00004: Superradiant emission from colour centres in diamond Invited Speaker: Johannes Majer Superradiance is a fundamental collective effect where radiation is amplified by the coherence of multiple emitters. Superradiance plays a prominent role in optics (where it enables the design of lasers with substantially reduced linewidths) and quantum mechanics, and is even used to explain cosmological observations such as Hawking radiation from black holes5. Resonators coupled to spin ensembles are promising future building blocks of integrated quantum devices that will involve superradiance. As such, it is important to study its fundamental properties within such devices. Although experiments in the strong-coupling regime have shown oscillatory behaviour in these systems, a clear signature of Dicke superradiance has so far been missing. Here we explore superradiance in a system composed of a three-dimensional lumped element resonator in the fast cavity limit inductively coupled to an inhomogeneously broadened ensemble of nitrogen–vacancy centres. We observe a superradiant pulse being emitted a trillion times faster than the decay for an individual nitrogen–vacancy centre. This is further confirmed by the nonlinear scaling of the emitted radiation intensity with respect to the ensemble size. Our work provides the foundation for future quantum technologies including solid-state superradiant masers. |
Thursday, March 7, 2019 3:42PM - 3:54PM |
V29.00005: Electron spin hyperpolarization via radiative cooling Bartolo Albanese, Sebastian Probst, Vishal Ranjan, Denis Vion, Emmanuel Flurin, Daniel Esteve, John Morton, Gengli Zhang, Ren-Bao Liu, Patrice Bertet Electron spin resonance (ESR) spectroscopy is widely employed for the detection and characterization of paramagnetic species [1]. A high degree of spin polarization is essential to maximize the signal. Here, we are interested in increasing the polarization beyond thermal equilibrium. Techniques such as optical pumping are available only for systems with special electronic structures. In the present work we give a proof of principle of a new universal hyperpolarization scheme based on the coupling of the electron spins to a colder electromagnetic bath via Purcell-enhanced radiative relaxation. A superconducting micro-resonator is used in order to reach the regime in which radiative relaxation constitutes the dominant mechanism of spin thermalization [2]. The spin system under study is an ensemble of bismuth donors implanted into a host silicon crystal. The sample is installed at the 800 mK stage of a dilution cryostat while the resonator is coupled via a switch either to a 10 mK or to a 800 mK thermal source. When the switch is connected to the colder black body, the electronic spins are cooled via radiative relaxation while the silicon crystal remains at 800 mK. |
Thursday, March 7, 2019 3:54PM - 4:06PM |
V29.00006: Coherent spin-wave excitations in an optically cooled nuclear ensemble Dorian Gangloff, Gabriel Ethier-Majcher, Constantin Lang, Emil Vosmar Denning, Jonathan Bodey, Daniel Jackson, Claire Le Gall, Mete Atature Collective excitations of isolated many-body systems offer the opportunity to control complex quantum dynamics. A simple quantum system, such as a central spin, can act as a probe and a control over a larger and more complex quantum system in ways otherwise intractable, and can help us perform spectroscopy and engineering over its quantum dynamics. Driving the central spin can stimulate exchange of energy with its surrounding spins, and thus modify the mean-field state of its own environment. In this work, we engineer this very interaction between an InGaAs quantum dot electron spin and its isolated ensemble of nuclear spins in a driven-dissipative regime to remove entropic heat from the ensemble, and so vastly reduce the mean-field state uncertainty tied to its thermal fluctuations. Having cooled the system, we reveal an absorption spectrum of transitions between many-body states that are collectively-enhanced by the creation of single spin-wave excitations – nuclear magnons. Resonantly driving such a transition, we stimulate coherent exchange of single magnons between the electron and the nuclear spin ensemble, which is consistent with the controlled creation of entanglement among all constituent particles. |
Thursday, March 7, 2019 4:06PM - 4:18PM |
V29.00007: High-Q Superconducting Mm-wave Cavities for Rydberg Cavity Quantum Electrodynamics. Aziza Suleymanzade, Alexander Anferov, Mark Stone, Jonathan Simon, David Schuster We will outline our progress towards a cryogenic hybrid experimental system for engineering strong interactions between single optical and mm-wave photons using Rydberg atoms as an interface. Bulk 3D cavities in the microwave regime routinely reach quality factors above 10^7 at single photon powers and even in some case as high as 10^10. At the same time there has been far less study of resonators at millimeter wave frequencies close to 100GHz. We present experimental results of superconducting fundamental mode niobium cavities at 100GHz, with quality factors exceeding 10^7. We will also present experiments showing tuning the cavity frequency in-situ, to be able to exactly match Rydberg transitions. |
Thursday, March 7, 2019 4:18PM - 4:30PM |
V29.00008: Accessing Nonlinearity in Superconducting Millimeter Wave Coplanar Resonators Alexander Anferov, Aziza Suleymanzade, Jonathan Simon, David Schuster Current superconducting quantum systems rely on ultra-cold temperatures to reduce sources of noise and quantum decoherence. While many advances have been made in the purification and refinement of quantum devices in the low microwave frequency range, millimeter frequencies have been far less explored. Using higher energy photons as a building block could potentially allow quantum experiments to be run faster, at higher temperatures, and easily access other high frequency quantum systems, such as Rydberg atoms. We use superconducting thin film materials to fabricate resonators with planar geometries to ensure scalability and direct compatibility with other elements in the superconducting quantum toolbox, while gaining a natural increase of kinetic inductance based nonlinear effects with frequency. Here, we present and characterize low-loss millimeter wave resonators with planar geometries exhibiting nonlinear behavior, demonstrating a scalable core component for a new generation of high frequency quantum devices. |
Thursday, March 7, 2019 4:30PM - 4:42PM |
V29.00009: Coupling a single electron on helium to a superconducting resonator Gerwin Koolstra, Ge I Yang, David Schuster Electrons on helium is a unique two-dimensional system on the interface of superfluid He-4 and vacuum. Both the motional state and spin state of a single electron on helium have been proposed as candidates for long-lived qubits. To trap a single electron on helium, we use a small electrostatic trap located at the voltage anti-node of a superconducting microwave resonator. By adjusting the trap potential we are able to consistently load between one and four electrons and detect their spectroscopic features through the resonator. In particular, in the single electron regime a large resonator frequency shift reveals when the electron motional frequency is resonant and allows us to extract an electron-photon coupling of ~ 10 MHz. I will highlight our latest experiments leading towards the development of an electron on helium qubit. |
Thursday, March 7, 2019 4:42PM - 4:54PM |
V29.00010: Thermopower based hot electron thermometry of helium surface states at 1.6 K Ethan Kleinbaum, Stephen Aplin Lyon Inelastic scattering processes are crucial for understanding and describing a wide variety of phenomena observed in surface state electrons (SSE) on helium including non-linear transport and microwave absorption line shapes. Further interest in inelastic scattering has been motivated by the relevance to coherence times of Rydberg state based SSE qubits. Despite their fundamental importance, relatively little experimental work have examined inelastic processes which can be attributed to challenges associated with electron thermometry of hot SSE. |
Thursday, March 7, 2019 4:54PM - 5:06PM |
V29.00011: Phase transitions in a strongly interacting electron system under confinement Niyaz Beysengulov, David G Rees, Mikhail Zakharov, Yurii Lysogorskiy, Kimitoshi Kono, Dmitrii Tayurskii Phase transition in a two-dimensional lattice is described by a Berezinskii-Kosterlitz-Thouless (BKT) mechanism. At low temperatures the ground state of strongly interacting 2D electron system is a Wigner solid, which was experimentally observed in a many experiments with electrons on the surface of liquid helium. A well controlled system of electrons on liquid helium provide an excellent platform to investigate a many-body phenomena. Here we investigate the influence of a quasi-one-dimensional confinement on the structural order and melting of electrons on helium experimentally and by numerical simulations. In the experiments electrons are confined by electrostatic potential in a microchannel structures. By tuning voltages on gate electrodes we were able to demonstrate the control of number of electron rows (from a single chain up to 25 rows). We show that for small number of rows gamma parameter (the ratio of Coulomb energy to thermal energy) is suppressed, while for large number of rows a BKT theory prediction is recovered. We compare the results with molecular dynamics simulations. The temperature dependence of topological defects density, translational correlation function and structure factor were calculated and discussed in the context of BKT transition. |
Thursday, March 7, 2019 5:06PM - 5:18PM |
V29.00012: Transport measurements of electrons above shallow helium-filled microchannels Abraham Asfaw, Ethan Kleinbaum, Stephen Aplin Lyon The spins of electrons floating on superfluid helium constitute a promising platform for quantum computation. Quantum devices for electrons on helium, such as electrostatically defined quantum dots, require gate electrodes that are patterned beneath thin helium films. This can be particularly challenging at helium depths below 1 μm, since the electrons can be trapped by potential fluctuations on the surface of the gate electrode resulting from surface roughness and variations in the work function. |
Thursday, March 7, 2019 5:18PM - 5:30PM |
V29.00013: Acoustoelectric transport of electrons on helium Heejun Byeon, Kostyantyn Nasyedkin, Justin Lane, Niyaz Beysengulov, Reza Loloee, Johannes Pollanen We report on the acoustoelectric transport of electrons on helium induced by coupling to piezoelectric surface acoustic waves (SAWs). In our device, the SAWs propagate along the surface of a lithium niobate piezoelectric crystal that is submerged beneath a thin layer of superfluid 4He. Electrons are deposited onto the superfluid and float ~10 nm above its surface. When SAWs propagate along the lithium niobate substrate, electrons are trapped in the moving electric potential of the SAW and transported across the device at the speed of the piezoacoustic wave. Electrodes positioned beneath the lithium niobate capacitively couple to the electrons and are used to detect acoustoelectric transport. We have performed time and frequency domain measurements and analysis to characterize the electric current dragged along by the SAW. To our knowledge, these measurements constitute the first demonstration of acoustoelectric charging pumping of electrons on helium. |
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