# Weekly Roundup for the Week Ending July 18, 2020

*If we could not find room for it, time to digest it, or a reason to run it during the past week, we have collected it here. Not a recap for the week, but a cleanup of pieces we received and just could not get to.*

*Because Quantum is Coming. Qubit*

## Algorithms & Software

**Quantum approximate Bayesian computation for NMR model inference**** | **Recent technological advances may lead to the development of small-scale quantum computers that are capable of solving problems that cannot be tackled with classical computers. A limited number of algorithms have been proposed and their relevance to real-world problems is a subject of active investigation. Analysis of many-body quantum systems is particularly challenging for classical computers due to the exponential scaling of the Hilbert space dimension with the number of particles. Hence, solving the problems relevant to chemistry and condensed-matter physics is expected to be the first successful application of quantum computers. In this Article, we propose another class of problems from the quantum realm that can be solved efficiently on quantum computers: model inference for nuclear magnetic resonance (NMR) spectroscopy, which is important for biological and medical research. Our results are based on three interconnected studies. First, we use methods from classical machine learning to analyse a dataset of NMR spectra of small molecules. We perform stochastic neighbourhood embedding and identify clusters of spectra, and demonstrate that these clusters are correlated with the covalent structure of the molecules. Second, we propose a simple and efficient method, aided by a quantum simulator, to extract the NMR spectrum of any hypothetical molecule described by a parametric Heisenberg model. Third, we propose a simple variational Bayesian inference procedure for estimating the Hamiltonian parameters of experimentally relevant NMR spectra. Source:* Quantum approximate Bayesian computation for NMR model inference… *

**Power-efficient combinatorial optimization using intrinsic noise in memristor Hopfield neural networks**** | **To tackle important combinatorial optimization problems, a variety of annealing-inspired computing accelerators, based on several different technology platforms, have been proposed, including quantum-, optical- and electronics-based approaches. However, to be of use in industrial applications, further improvements in speed and energy efficiency are necessary. Here, we report a memristor-based annealing system that uses an energy-efficient neuromorphic architecture based on a Hopfield neural network. Our analogueâ€“digital computing approach creates an optimization solver in which massively parallel operations are performed in a dense crossbar array that can inject the needed computational noise through the analogue array and device errors, amplified or dampened by using a novel feedback algorithm. We experimentally show that the approach can solve non-deterministic polynomial-time (NP)-hard max-cut problems by harnessing the intrinsic hardware noise. We also use experimentally grounded simulations to explore scalability with problem size, which suggest that our memristor-based approach can offer a solution throughput over four orders of magnitude higher per power consumption relative to current quantum, optical and fully digital approaches. Source:* Power-efficient combinatorial optimization using intrinsic noise in memristor Hopfield neural networks…*

## Technology & Hardware

**Molecular docking with Gaussian Boson Sampling**** | **Gaussian Boson Samplers are photonic quantum devices with the potential to perform intractable tasks for classical systems. As with other near-term quantum technologies, an outstanding challenge is to identify specific problems of practical interest where these devices can prove useful. Here, we show that Gaussian Boson Samplers can be used to predict molecular docking configurations, a central problem for pharmaceutical drug design. We develop an approach where the problem is reduced to finding the maximum weighted clique in a graph, and show that Gaussian Boson Samplers can be programmed to sample large-weight cliques, i.e., stable docking configurations, with high probability, even with photon losses. We also describe how outputs from the device can be used to enhance the performance of classical algorithms. To benchmark our approach, we predict the binding mode of a ligand to the tumor necrosis factor-Î± converting enzyme, a target linked to immune system diseases and cancer. Source:* Science Advances. Leonardo Banchi, Mark Fingerhuth, Tomas Babej, Christopher Ing, Juan Miguel Arrazola Molecular docking with Gaussian Boson Sampling… *

**A monolithic bipolar CMOS electronicâ€“plasmonic high-speed transmitter**** | ** Source:* Nature.com . Koch, U., Uhl, C., Hettrich, H. et al. A monolithic bipolar CMOS electronicâ€“plasmonic high-speed transmitter… *

**Electric fields control spintronics devices**** | **A new low-power technique for detecting the spin of electrons in a non-magnetic system could aid the development of spintronics devices that work using ferroelectricity rather than ferromagnetism. Such devices may eventually form the backbone of a new generation of efficient, low-energy computer processors, and thus help maintain progress in high-speed information processing. Source:* physcisworld. Isabelle Dume Electric fields control spintronics devices…*

## Science & Research

**Unusual state of matter holds promise for transformative quantum technologies**** | **(Nanowerk News) ANSTO has provided supporting experimental evidence of a highly unusual quantum state, a quantum spin liquid (QSL), in a two-dimensional material as reported by an international collaboration led by Tokyo University in Nature Communications (“Gapless spin liquid in a square-kagome lattice antiferromagnet”). Source:* Nanowerk News. Nanowerk News Unusual state of matter holds promise for transformative quantum technologies… *

**Spontaneous creation and annihilation dynamics and strain-limited stability of magnetic skyrmions**** | **Magnetic skyrmions are topological magnetic spin structures exhibiting particle-like behaviour. They are of strong interest from a fundamental viewpoint and for application, where they have potential to act as information carriers in future low-power computing technologies. Importantly, skyrmions have high physical stability because of topological protection. However, they have potential to deform according to their local energy environment. Here we demonstrate that, in regions of high exchange energy density, skyrmions may exhibit such extreme deformation that spontaneous merging with nearest neighbours or spawning new skyrmions is favoured to attain a lower energy state. Using transmission electron microscopy and a high-speed imaging detector, we observe dynamics involving distinct configurational states, in which transitions are accompanied by spontaneous creation or annihilation of skyrmions. These observations raise important questions regarding the limits of skyrmion stability and topological charge conservation, while also suggesting a means of control of skyrmion creation and annihilation. Source:* nature communications. Rendell-Bhatti, F., Lamb, R.J., van der Jagt, J.W. et al. Spontaneous creation and annihilation dynamics and strain-limited stability of magnetic skyrmions…*

**2-D semiconductors found to be close-to-ideal fractional quantum Hall platform**** | **Columbia University researchers report that they have observed a quantum fluid known as the fractional quantum Hall states (FQHS), one of the most delicate phases of matter, for the first time in a monolayer 2-D semiconductor. Their findings demonstrate the excellent intrinsic quality of 2-D semiconductors and establish them as a unique test platform for future applications in quantum computing. The study was published online today in Nature Nanotechnology. Source:* Phys.org. Columbia University School of Engineering and Applied Science 2-D semiconductors found to be close-to-ideal fractional quantum Hall platform…*

**Supertransport of excitons in atomically thin organic semiconductors at the 2D quantum limit**** | **Long-range and fast transport of coherent excitons is important for the development of high-speed excitonic circuits and quantum computing applications. However, most of these coherent excitons have only been observed in some low-dimensional semiconductors when coupled with cavities, as there are large inhomogeneous broadening and dephasing effects on the transport of excitons in their native states in materials. Here, by confining coherent excitons at the 2D quantum limit, we first observed molecular aggregation-enabled â€˜supertransportâ€™ of excitons in atomically thin two-dimensional (2D) organic semiconductors between coherent states, with a measured high effective exciton diffusion coefficient of ~346.9â€‰cm2/s at room temperature. This value is one to several orders of magnitude higher than the values reported for other organic molecular aggregates and low-dimensional inorganic materials. Without coupling to any optical cavities, the monolayer pentacene sample, a very clean 2D quantum system (~1.2â€‰nm thick) with high crystallinity (J-type aggregation) and minimal interfacial states, showed superradiant emission from Frenkel excitons, which was experimentally confirmed by the temperature-dependent photoluminescence (PL) emission, highly enhanced radiative decay rate, significantly narrowed PL peak width and strongly directional in-plane emission. The coherence in monolayer pentacene samples was observed to be delocalised over ~135 molecules, which is significantly larger than the values (a few molecules) observed for other organic thin films. In addition, the supertransport of excitons in monolayer pentacene samples showed highly anisotropic behaviour. Our results pave the way for the development of future high-speed excitonic circuits, fast OLEDs, and other optoelectronic devices. Source:* nature.com. Ankur Sharma, etal. Supertransport of excitons in atomically thin organic semiconductors at the 2D quantum limit…*

## Government & Policy

**NDAA could require closer tracking of DOD researchers**** | **House lawmakers last week passed an amendment to the 2021 National Defense Authorization Act that would allow the Defense Department to track U.S. and foreign student researchers on national security projects, despite privacy concerns. Source:* FCW. Lauren C. Williams NDAA could require closer tracking of DOD researchers… *

## Business & Industry

**Why is Quantum Computing Gaining Popularity?**** | **ecently, Google announced that achieving quantum supremacy will undoubtedly grab a lot of attention. Although there are a lot of questions about what the achievement means, businesses and academia will continue to make strides towards manufacturing a commercial quantum computer and refining quantum security techniques. The last decade was filled with significant trends, all of which will continue to play even now. In this decade, a new beginning, let’s read what might hold for quantum computing and its ecosystem of supporting technologies. Source:* CIO Review. CIO Review Why is Quantum Computing Gaining Popularity?*

## Cybersecurity & Cryptography

**QuintessenceLabs Wins Prestigious Global CyberTech 100 Award | **Source:* businesswire. QuintessenceLabs, QuintessenceLabs Wins Prestigious Global CyberTech 100 Awardâ€¦ *