Tyler O'Neal, Staff Editor PHYSICS

Rochester researchers set ultrabroadband record with entangled photons

The engineers have achieved unprecedented bandwidth and brightness on chip-sized nanophotonic devices.

Quantum entanglement or what Albert Einstein once referred to as “spooky action at a distance” occurs when two quantum particles are connected, even when millions of miles apart. Any observation of one particle affects the other as if they were communicating with each other. When this entanglement involves photons, interesting possibilities emerge, including entangling the photons’ frequencies, the bandwidth of which can be controlled.

Researchers at the University of Rochester have taken advantage of this phenomenon to generate an incredibly large bandwidth by using a thin-film nanophotonic device they describe in Physical Review Letters.

The breakthrough could lead to:

  • Enhanced sensitivity and resolution for experiments in metrology and sensing, including spectroscopy, nonlinear microscopy, and quantum optical coherence tomography
  • Higher-dimensional encoding of information in quantum networks for information processing and communications

“This work represents a major leap forward in producing ultra-broadband quantum entanglement on a nanophotonic chip,” says Qiang Lin, professor of electrical and computer engineering. “And it demonstrates the power of nanotechnology for developing future quantum devices for communication, computing, and sensing,” Researchers in the lab of Qiang Lin at the University of Rochester have generated record ‘ultrabroadband’ bandwidth of entangled photons using the thin-film nanophotonic device illustrated here. At top left, a laser beam enters a periodically poled thin-film lithium niobate waveguide (banded green and gray). Entangled photons (purple and red dots) are generated with a bandwidth exceeding 800 nanometers. (Illustration by Usman Javi and Michael Osadciw)

No more tradeoff between bandwidth and brightness

To date, most devices used to generate broadband entanglement of light have resorted to dividing up a bulk crystal into small sections, each with slightly varying optical properties and each generating different frequencies of the photon pairs. The frequencies are then added together to give a larger bandwidth.

“This is quite inefficient and comes at a cost of reduced brightness and purity of the photons,” says lead author Usman Javid, a Ph.D. student in Lin’s lab. In those devices, “there will always be a tradeoff between the bandwidth and the brightness of the generated photon pairs, and one has to make a choice between the two. We have completely circumvented this tradeoff with our dispersion engineering technique to get both: a record-high bandwidth at a record-high brightness.”

The thin-film lithium niobate nanophotonic device created by Lin’s lab uses a single waveguide with electrodes on both sides. Whereas a bulk device can be millimeters across, the thin-film device has a thickness of 600 nanometers—more than a million times smaller in its cross-sectional area than a bulk crystal, according to Javid. This makes the propagation of light extremely sensitive to the dimensions of the waveguide.

Indeed, even a variation of a few nanometers can cause significant changes to the phase and group velocity of the light propagating through it. As a result, the researchers’ thin-film device allows precise control over the bandwidth in which the pair-generation process is momentum-matched. “We can then solve a parameter optimization problem to find the geometry that maximizes this bandwidth,” Javid says.

The device is ready to be deployed in experiments, but only in a lab setting, Javid says. To be used commercially, a more efficient and cost-effective fabrication process is needed. And although lithium niobate is an important material for light-based technologies, lithium niobate fabrication is “still in its infancy, and it will take some time to mature enough to make financial sense,” he says.

Other collaborators include coauthors Jingwei Ling, Mingxiao Li, and Yang He of the Department of Electrical and Computer Engineering, and Jeremy Staffa of the Institute of Optics, all of whom are graduate students. Yang He is a postdoctoral researcher.

Duke refines weather forecasts with the inclusion of small, sharp landscape contrasts

Tyler O'Neal, Staff Editor PHYSICS

Landscape features have an outsized effect on the accuracy of climate and weather models

By leveraging a popular weather forecasting model, environmental engineers at Duke University have demonstrated that sharp contrasts in relatively small land features play an outsized role in local weather developments, which can in turn influence larger climate trends. The study indicates that the addition of such detailed data, which is currently overlooked in climate and weather forecast models, should make such predictions more accurate. By including sharp contrasts in land features on small scales, a new study focusing on a 100x100 km box (shown here) improved the accuracy of weather and climate predictions. CREDIT Nate Chaney, Duke University

The results appear online on October 27 in the Journal of Advances in Modeling Earth Systems (JAMES).

“Our research illustrates that landscape heterogeneity, such as croplands next to a city, or a lake next to a forest, can lead to more powerful thunderstorms,” said Nathaniel Chaney, assistant professor of civil and environmental engineering at Duke.

“What makes this important is that the scale at which these patterns happen is smaller than what we can include in current global models,” added Jason Simon, a postdoctoral associate working in Chaney’s laboratory and first author of the paper.

Whether making long-term global climate predictions or short-term weather predictions, climatologists and meteorologists turn to a handful of global models (e.g., the United States uses the Global Forecasting System). One of the limitations of these models is the scale at which they make their calculations. To avoid months of simulation runtime, these models split the Earth’s surface into boxes measuring between 10 to 100 kilometers (62.1 miles) per side. Variables such as temperature, wind speed, and moisture are directly calculated at each node where the corners of these boxes meet but are interpolated or averaged for all the space between them.

“That’s a large distance between points, in which there’s plenty of patterns causing changes on their own,” Simon said. “It’s a whole aspect of weather that’s being missed. And if it involves clouds, then it’s going to have a large impact on the energy balance in relation to climate change on a global scale.”

In their study, Chaney and Simon used a higher-resolution weather model, the Weather and Research Forecasting model (WRF) to see what effect sharply defined changes in soil moisture at a 100-meter spatial resolution have on cloud formation. They focused on a 100-kilometer box over north-central Oklahoma on three summer days, considering landscape patterns where small lakes and rivers lay next to forests or thunderstorm-drenched plains, for example. Acquiring actual ground data from specific days ensured that the small-scale features they used were accurate representations of the real world.

After running the simulations, the results showed that sharp differences in the landscape at these scales can have a disproportionately large effect on the formation of clouds. For example, a drier, hotter area next to a cooler, moister area — like an area where plains and cities meet — will create surface atmospheric pressure differences between the dry and moist regions that trigger secondary circulations in the atmosphere. These circulations, in turn, lead to the enhanced formation of clouds.

While this is not the first study to reveal these sorts of dynamics, it is the first that uses realistic land surface data versus statistically simulated spatial patterns that may or may not reflect reality. It is also novel in its spatial resolution, which was shaved down to just 100 meters in the Weather and Research Forecasting model. 

Chaney and Simon say that it would take a lot of work to get global models like the Global Forecasting System to be able to run simulations with this scale of land surface data included. But according to their new results, it could be possible if researchers adopted the tricks used by Chaney’s group to simulate high-resolution landscape spatial patterns.

“Whether it’s a multi-year global climate model or a local daily forecast, incorporating this level of detail would improve their accuracy,” Simon said.

“In the summer months — especially in North Carolina — we don’t know if it’s going to storm until it’s almost raining on us,” added Chaney. “Using this approach in a forecasting model could help us know several hours in advance.”

The three horsemen of cyber risks: Misinformation, disinformation, fake news

Tyler O'Neal, Staff Editor PHYSICS

The risks associated with misleading information can have a profoundly negative impact. A study aims to provide recommendations on responding to the new digital age challenges

Misleading information has emerged as one of the leading cyber risks in our society, affecting political leaders, nations, and people’s lives, with the COVID-19 pandemic having only made it worse. However, it also affects something we rarely stop to consider: business. But how do organizations prepare against such threats? A new study, in Business Horizons, published by Elsevier, maps out the risk factors associated with misinformation, disinformation, and fake news—proposing practical ways to manage risks in the parlance of business.

Industry 4.0 has brought about a metamorphosis in the world of business. The new revolution demands the integration of physical, biological, and digital systems under one roof. Such a transformation, however, comes with its own set of risks. Misleading information, including misinformation, disinformation, and fake news, often has damaging effects on the public image of political leaders and, as the COVID-19 crisis has clearly shown, on the general public and the economy. However, the consequences of misinformation on business organizations have been far less explored. To survive in the information era, organizations and individuals should have an understanding of risks associated with misleading information. A new study on this front has now underscored the risks of cyber threat in the world of business (Courtesy of: pixel2013 from Pixabay).

“Information has always played an irrefutable role in economics,” said Dr. Pythagoras N. Petratos of Coventry University’s Business School, whose research, examines the various forms of misleading information, identifying the cyber threats associated with them, and providing recommendations on tackling such risks. “We need to pay attention to the quality of information disseminated into the world, now more than ever, as spreading misinformation has become a lot easier with the advent of digital transformation.

“My research attempts to bridge the divide between academic research and real-world practice of cyber risk management.”

The fake news “infodemic” that spread alongside the COVID-19 pandemic also affected the finance sector. For instance, during the lockdown period of 2020, there was a huge surge in fake news and illegal activity related to the financial and other markets. Financial firms had to train their staff to deal with fraudulent online schemes and reports.

Deliberate spreading of disinformation has also been responsible for swaying the outcome of elections. Cyber attackers have used misleading information on social media for procuring campaign finances as well as personal and financial information of people and corporations. These actions undermine a nation's security and make them vulnerable to geopolitical risks.

To deal with these cyber risks, businesses and authorities need to establish cybersecurity practices and policies that can evolve and adapt to the multifaceted cyberthreats. Executives and leaders should be trained to recognize cyber threats when they see one. To enable faster recognition, firms need to embrace modern computing software that fits their work criteria and can detect, report, and effectively manage cyber threats.

Anti-misinformation strategies such as having human fact-checkers for websites or artificial intelligence for bot detection on social media could be used to prevent the damage caused by the propagation of misleading information. Partnerships between private and public sectors can also mitigate cyber risks by forming a united front with better cyber defenses and funds to invest in cyber security technologies.

All in all, the study provides a primer on the risks associated with misleading information in the sphere of business and the ways to avoid them, highlighting the fact that businesses are not immune to them either.

“Fake news is not a new phenomenon, but the COVID-19 pandemic, the ongoing digital transformations, and advances in big data have exacerbated it. Business executives and leaders across an array of industries, organizations, and nations, as well as the public, need to become aware of such risks and find innovative ways to manage them,” concludes Dr. Petratos.