Graduate

Spin qubits based on diamond NV centers can detect tiny magnetic fields; thin two-dimensional materials produce tiny magnetic fields. Do they make a good match? I will discuss two works that explored how NV magnetometry can uniquely probe the spins and currents in crystals that are one-atom thick.

Outline:
How we discovered, via local magnetic noise measurements, that graphene electrons at high bias undergo cherenkov radiation of phonons
How we performed the first NMR measurement on a single-atom thick crystal.
Some thoughts and outlook on the benefits and challenges of using spin qubits to measure condensed matter systems.
Preview of UC Irvine work on nanomanipulation of 2d material heterostructures

References:
"Electron-phonon instability in graphene revealed by global and local noise probes"
T. I. Andersen*, B. L. Dwyer*, J. D. Sanchez-Yamagishi*, J. F. Rodriguez-Nieva, K. Agarwal, K. Watanabe, T. Taniguchi, E. A. Demler, P. Kim, H. Park, M. D. Lukin
Science 364 ,6436 (2019) *equal contribution

"Magnetic resonance spectroscopy of an atomically thin material using a single-spin qubit"
I. Lovchinsky, J. D. Sanchez-Yamagishi, E. K. Urbach, S. Choi, S. Fang, T. Andersen, K. Watanabe, T. Taniguchi, A. Bylinskii, E. Kaxiras, P. Kim, H. Park, and M. D. Lukin
Science 355, 6324 (2017)

Gallium nitride (GaN) nanoelectronics have operated at temperatures as high as 1000°C making it a viable platform for robust space-grade ("tiny-but-tough") sensorsand electronics. In addition, there has been a tremendous amount of research and industrial investment in GaN as it is positioned to replace silicon in the billion-dollar (USD) power electronics industry, as well as the post-Moore microelectronics universe. Furthermore, the 2014 Nobel Prize in physics was awarded for pioneering research in GaN that led to the realization of the energy-efficient blue light-emitting diode (LED). Even with these major technological breakthroughs, we have just begun the "GaN revolution." New communities are adopting this nanoelectronic platform for a multitude of emerging device applications including the following: sensing, energy harvesting, actuation, and communication. In this talk, we will review and discuss the benefits of GaN's two-dimensional electron gas (2DEG) over silicon's p-n junction for space exploration applications (e.g., radiation-hardened, temperature-tolerant Venus instrumentation). In addition, we will discuss recent results that advance this nanoelectronic device platform for extreme-environment Internet-of-things (IoT)sensors for combustion and down-hole monitoring.

The exchanges of carbon dioxide (CO2) and methane (CH4) between arctic ecosystems and the atmosphere are sizeable and may if they change may alter the further development of climate warming. These fluxes take place between the atmospheric background of these trace gases and a very large reservoir of organic carbon stored in arctic soils and sediments. The stored carbon amounts to more than twice the current global atmospheric burden of CO2. Therefore, accurate measurements of the fluxes and how they vary temporally and spatially is key to understanding possible ecosystem impacts on the atmospheric mixing ratios and hence climate.
This presentation will detail the current state of the global CO2 and CH4 budget and review methods applied in quantifying the arctic trace gas flux components. The presentation will show new developments in the attempts to use UAV's to help improve spatial coverage of measured fluxes. The challenges in applying the laser techniques needed for the precise and fast trace gas measurements under true arctic conditions will be discussed.

Talk Title #1: A photonic quantum computer design with only one controllable qubit

Ben Bartlett (Stanford University, Prof. Shanhui Fan's group)

We describe a design for a photonic quantum computer which requires minimal quantum resources: a single coherently-controlled atom. Quantum operations applied to the atomic qubit can be teleported onto the photonic qubits via projective measurement, and arbitrary quantum circuits can be compiled into a sequence of these teleported operators. The proposed device has a machine size which is independent of quantum circuit depth, does not require single-photon detectors, operates deterministically, and is robust to experimental imperfections.

Talk title #2: Towards MEMS-driven photonic computing

Sunil Pai (Stanford University, advised by Prof. Olav Solgaard and co-advised by Profs. David Miller and Shanhui Fan)

ABSTRACT: Programmable nanophotonic networks of Mach-Zehnder interferometers are energy-efficient circuits for matrix-vector multiplication that benefit a wide variety of applications such as artificial intelligence, quantum computing and cryptography. In this talk, we discuss the theory and algorithms to set up field-programmable photonic networks using MEMS (microelectromechanical systems)-actuated phase shifts, which unlike currently more commonplace thermal phase shifters, cost no energy to maintain a constant phase shift and therefore significantly improve overall energy efficiency. We discuss the corresponding implications on gradient-based optimization (on-chip machine learning), scalability and dispersion of such networks for commercial applications such as training and inference in photonic neural networks, optical cryptocurrency, and low-loss quantum computers. We will then attempt a live demonstration of programming a small thermally-driven 6x6 triangular photonic network and observe the practical considerations such as thermal drift, dispersion, and phase shift calibration in these devices.

In 1965 Gordon Moore, co-founder of Fairchild Semiconductors and also Intel Corporation, predicted that the number of transistors per die would double every year until 1975 if specific actions were taken to eliminate any inflection points. This represents the first example of a long-term roadmap for semiconductors.

By 1975 data showed his predictions to be correct. He then predicted that the number of transistors would double every two years for the foreseeable future if appropriate actions were taken. Following Gordon Moore's demonstrated success of the roadmap methodology, the National Technology Roadmap for Semiconductors (NTRS) was formed in 1991 in the US; the roadmap became international (ITRS) in 1998 to collectively address a major inflection point (i.e., the end of the planar MOS silicon gate process). Following the ITRS recommendations the semiconductor industry sequentially developed in a very timely fashion Strained Silicon, High-K/Metal-Gate and FinFET into manufacturing. Beginning with 2016 the scope of the roadmap was extended to also include System and Architecture as well as trends on Cryogenic Electronics and Quantum Information Processing. In the not-too-distant future 2D space in ICs will reach fundamental limits and fully utilization of the third dimension (3D) to increase "functionality density" has already started. Furthermore homogeneous and heterogeneous integration of multiple technologies is already in progress and will become the way of the future. New recommendations for actions to be taken in the next 15 years have been formulated and will be presented.

Defect spin qubits in silicon carbide (SiC) with associated nuclear spin quantum memories can leverage near-telecom emission and wafer-scale semiconductor device engineering for creating quantum technologies. Here, I highlight recent advances with the neutral divacancy defect (VV0) in SiC within the context of long-distance quantum communication and repeater schemes. Broadly, I will illustrate how quantum states can be controlled, tuned, and enhanced through their integration into SiC mechanical, photonic, and electrical devices. I will first describe the isolation of single VV0 defects in functional SiC optoelectronic devices, which allows for deterministic charge state control and terahertz tuning, but also surprisingly eliminates spectral diffusion in the optical structure of these defects. I will then discuss the entanglement and control of nuclear spin registers, and show how isotopic engineering can enhance both nuclear quantum memories and electron spin coherence times, while also demonstrating high fidelity control (99.98%), initialization, and readout. Briefly, I will further highlight recent results that universally protect spin coherence from electrical, magnetic, and thermal noise, resulting in T2*>20 ms in a naturally abundant crystal. This suite of results establishes SiC as a promising platform for scalable quantum science with optically-active spins.

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