Bulletin of the American Physical Society
2018 Annual Meeting of the APS Mid-Atlantic Section
Volume 63, Number 20
Friday–Sunday, November 9–11, 2018; College Park, Maryland
Session G06: Light, Solids, and Quantum Information |
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Chair: Liang Wu, University of Pennsylvania Room: Edward St. John 2208 |
Saturday, November 10, 2018 4:00PM - 4:36PM |
G06.00001: Tuning properties of deep defects in hexagonal boron nitride: an ab-initio study Invited Speaker: Pratibha Dev In recent years, atom-like deep defects in semiconductors have emerged as promising solid-state qubits (quantum bits) for applications in different quantum technologies. Defects in bulk 3D semiconductors, such as the charged NV-center in diamond and divacancies in SiC, are better-known defects and have been more widely studied. However, increasingly, there is an interest in exploring quantum emitters in layered 2D semiconductors. As compared to a 3D semiconductor, the 2D structure of a layered material offers better control of the location of the deep defect in the 2D-matrix, providing a scalable platform for quantum applications. In addition, the surface-only structure of the layered materials makes it possible to tune their properties and hence, the properties of the defects within the 2D structures. This can be achieved by controlling various factors, such as: (a) the number of the layers and their composition and, (b) the applied strain. The density functional theory-based results presented here show that the deep defects in hexagonal boron nitride (hBN) have high-spin ground states even at room-temperature, making them viable solid-state qubit candidates in a layered material. We further demonstrate that strain can be used to tune the electronic, spin and optical properties of these quantum emitters within the layers. |
Saturday, November 10, 2018 4:36PM - 4:48PM |
G06.00002: Spin-Selective Energy Level Modification via the AC Stark Effect in a Quantum Dot Dillion J Cottrill, Tristan A Wilkinson, Josh M Cramlet, Cole E Maurer, Collin J Flood, Allan Bracker, Edward B Flagg Applying a strong laser far detuned from the resonance of a charged quantum dot causes an AC Stark shift of the energy levels, where the magnitude and direction of the shift is dependent upon the polarization, detuning, and intensity of the laser. The polarization also determines which spin manifold is shifted with circular polarization shifting only one spin projection. There is also a secondary energy shift, which is very likely caused by dynamic nuclear polarization, or the transfer of spin polarization from electron to nuclei, manifesting itself in the form of the Overhauser effect. In principle, the AC Stark effect in a Voigt geometry magnetic field will allow read out of the spin state of a quantum dot. |
Saturday, November 10, 2018 4:48PM - 5:00PM |
G06.00003: Construction and Analysis of an Inexpensive Arduino-Based Rotating Quarter-Wave Plate Stokes Polarimeter Cole E Maurer, Collin Flood, Tristan Wilkinson, Edward B Flagg Optical manipulation of self-assembled quantum dots relies heavily on the polarization of the light sources used to control them. In order to quickly measure the polarization at various points in the optical path, we have created an inexpensive polarimeter that is able to determine the polarization of incoming light by passing it through a rotating quarter-wave plate, a stationary polarizer, and measuring the light intensity with a photodiode. An Arduino microcontroller performs the analysis, conducting a Fourier transform on the intensity signal then analyzing the frequency components. Updating four times per second, an LCD displays the Stokes Vector to three significant figures, accurately providing a real-time measurement of the polarization. The electrical and mechanical components for the device cost less than $200, and no other elements – such as an oscilloscope – are necessary for the measurement. |
Saturday, November 10, 2018 5:00PM - 5:36PM |
G06.00004: New Color Centers in Diamond for Quantum Networks Invited Speaker: Paul Stevenson Communication between quantum nodes is a key step in realizing the potential of quantum computers. However, this communication is fundamentally different from its classical analog, and so requires fundamentally new approaches - including new hardware. I will present recent efforts to engineer and characterize a promising new quantum resource - the neutral silicon vacancy (SiV0) in diamond. SiV0 is a point defect in diamond, comprised of a substitutional silicon and a vacant carbon site. Point defects in diamond offer an atom-like system in a solid-state host with low magnetic noise. The nitrogen vacancy (NV) center has already been used to demonstrate several key elements of a quantum network; however, the optical transitions are not well-suited to network applications. Conversely, the negatively-charged silicon vacancy (SiV-) has excellent optical properties, but poor spin coherence times. By carefully engineering the Fermi level of diamond, we are able to access a new silicon vacancy charge state, SiV0, which combines the long spin coherence times of NV (T2,CPMG>200ms) and the favorable optical properties of SiV-. |
Saturday, November 10, 2018 5:36PM - 5:48PM |
G06.00005: Direct three-dimensional measurement of refractive index via dual Brillouin scattering Antonio Fiore, Carlo Bevilacqua, Giuliano Scarcelli The spatial distribution of refractive index can help understanding several biomedical phenomena. However, current techniques to map refractive index rely on the measure of the phase delay induced by the sample. This approach requires knowing, measuring or assuming the geometrical path of the light, which is not trivial in most experimental conditions. To overcome these limitations, we designed a novel confocal microscopy technique based on two co-localized Brillouin scattering interactions probed inside a confocal voxel. The ratio between the two Brillouin shifts only depends on the local refractive index, which can therefore be determined in a direct manner, without assumptions on the size, symmetry or shape. To test the consistency of our measurement, we compared the results of the dual Brillouin spectroscopy with a standard Abbe refractometer, obtaining strong agreement between the two methods (R2>0.99), reaching an accuracy of 10-3 RIU. To validate our 3D mapping capability we imaged a XY and a XZ section of a polymer drop, obtaining the correct index of refraction. |
Saturday, November 10, 2018 5:48PM - 6:00PM |
G06.00006: Building a Predictive Tool-Chain for Superconducting Qubits Tomasz M. Kott, Andrew C. Strikwerda, Dennis G. Lucarelli, Jeffrey P. Barnes, Kyle P. McElroy, Philip R Johnson In this presentation we present a superconducting qubit modeling tool chain which of the energy levels (spectrum) of a particular circuit based on the knowledge of fabrication technology and the layout of the circuit. The combination of this information allows software to produce a virtually fabricated circuit. Importantly, the tool is not meant to fit data to provide retrospective information about various parameters – the key is to take existing experimental fabrication parameters, such as critical current, and predict the energy spectrum of circuits and resonators that have not been tested yet. In this talk, we show that we were able to create a toolkit that predicted the cavity frequencies, the charging energies, and the coupling to within 20% accuracy. We discuss limiting factors in the computational electromagnetic models and experimental understanding of critical parameters that limits the accuracy of our predictive tool. |
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