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Chip that steers terahertz beams sets stage for ultrafast internet of the future

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theconversation.com – Ranjan Singh, Professor of Electrical Engineering, University of Notre Dame – 2024-09-03 08:01:19

The angles and branches in this illustration of a chip are key to using terahertz waves for the next generation of high-speed wireless communications.
Wenhao Wang, Guillaume Ducournau, and Ranjan Singh

Ranjan Singh, University of Notre Dame

Imagine a future where internet connections are not only lightning-fast but also remarkably reliable, even in crowded spaces. This vision is rapidly approaching reality, thanks to new research on terahertz communications technologies. These innovations are set to transform wireless communication, particularly as communications technology advances toward the next generation of networks, 6G.

I’m an engineer who focuses on photonics, the study of how light and other electromagnetic waves are generated and detected. In this research, my colleagues and I have developed a silicon topological beamformer chip. Topological refers to physical features in the silicon that help steer terahertz waves, and beamformer refers to the purpose of the chip: forming terahertz waves into directed beams.

Terahertz frequencies are crucial for 6G, which telecommunications companies plan to roll out around 2030. The radio frequency spectrum used by current wireless networks is becoming increasingly congested. Terahertz waves offer a solution by using the relatively unoccupied portion of the electromagnetic spectrum between microwaves and infrared. These higher frequencies can carry massive amounts of data, making them ideal for the data-intensive applications of the future.

beams shoot out from a chip with angled circuits
An experimental chip represented in this illustration spreads ultrafast terahertz beams in all directions around it.
Wenhao Wang, Guillaume Ducournau, and Ranjan Singh

Our chip takes a terahertz signal from a single source and splits it into 54 smaller signals, which are then guided through 184 tiny channels with 134 sharp turns. Each beam can transmit and receive data at speeds of 40 to 72 gigabits per second, many times faster than today’s 5G networks.

With the help of artificial intelligence, we designed the chip to have a specific microscopic honeycomb pattern to form lanes for the terahertz waves. The array of channels sends out powerful, focused beams that cover the entire 360 degrees around the chip. This allows a phone or other wireless device anywhere around a Wi-Fi router or other communications device using the chip to receive the high-speed signal. We demonstrated the chip by splitting an input signal of a streaming HD video into four output beams.

Beamformers in wireless networks

Terahertz waves have a shorter range compared with lower-frequency signals used in 4G and 5G networks. Terahertz beamformers address this challenge by precisely directing high-frequency signals to ensure they reach their destination without loss or degradation.

Beamformers are essential for the next generation of wireless communication. Unlike traditional antennas that broadcast signals indiscriminately, beamformers focus signals in specific directions, boosting both efficiency and reliability. Our chip ensures that those beams provide coverage in all directions.

This focused approach not only extends the signal’s range but also improves its quality, even over long distances. Beamformers are likely to be crucial in managing stable connections by reducing interference as the world adds billions of connected devices.

A future with terahertz beamforming

The potential impact of terahertz beamforming chips on everyday life is profound. For example, these chips could make it possible to download a 4K ultrahigh-definition movie in mere seconds compared with 11 minutes over today’s W-Fi, or support immersive virtual and augmented reality experiences without any lag.

Beyond entertainment, they could make real-time holographic communication a reality, where people appear as lifelike holograms. Smart cities could use this technology to seamlessly coordinate traffic systems and emergency responses, while health care could benefit from remote surgeries where doctors control robotic instruments from afar.

The terahertz beamforming chip represents a significant step forward on the path to faster, more reliable wireless communication by overcoming the challenges of high-frequency signal transmission.The Conversation

Ranjan Singh, Professor of Electrical Engineering, University of Notre Dame

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Can Trump just order new names for Denali and the Gulf of Mexico? A geographer explains who decides what goes on the map

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theconversation.com – Innisfree McKinnon, Associate Professor of Geography, University of Wisconsin-Stout – 2025-01-24 15:02:00

Known as Mount McKinley until 2015, Denali’s current name reflects what Native Alaskans call the mountain.
Arterra/Universal Images Group via Getty Images

Innisfree McKinnon, University of Wisconsin-Stout

President Donald Trump’s executive order to rename the Gulf of Mexico and Alaska’s Denali, the tallest peak in the country, has resulted in lots of discussion. While for some, such renaming might seem less important than the big problems the country faces, there is a formal process in the United States for renaming places, and that process is taken seriously.

Usually, so people don’t get confused, official, agreed-upon names are used by the government. In the U.S., place names are standardized by the U.S. Board on Geographic Names, which is part of the U.S. Geological Survey, the agency in charge of making maps.

In his executive order, Trump asks the Board on Geographic Names “to honor the contributions of visionary and patriotic Americans” and change its policies and procedures to reflect that.

Usually, renaming a place starts locally. The people in the state or county propose a name change and gather support. The process in each state is different.

A lake with sailboats and a city skyline in the background
Lake Bde Maka Ska, formerly Lake Calhoun, is the largest lake in Minneapolis.
YinYang/E+ via Getty

How to change a place name

Minnesota recently changed the name of a large lake in Minneapolis to Bde Maka Ska, which the Minneapolis Park Board described as “a Dakota name for the lake that has been passed down in oral history for many years.”

The board voted to change the name and took its request to the county commissioners. When the county agreed, the request was then sent to the Minnesota Department of Natural Resources, which made it official for Minnesota. Then, the state of Minnesota sent the request to the Board on Geographic Names, which made it official for the entire U.S.

It’s a lot of paperwork for something so seemingly minor, but people get passionate about place names. It took 40 years to rename Denali from the name established in the late 19th century, Mount McKinley.

The state of Alaska requested the name change in 1975, but the Board on Geographic Names didn’t take action. Members of the Ohio congressional delegation – President William McKinley was from Ohio – objected over many years to requests to rename the mountain, and the board did not act on those requests.

The president appoints the secretary of the Interior Department. The secretary works with the heads of related agencies to appoint the Board on Geographic Names. Current committee policy states, “Input from State geographic names authorities, land
management agencies, local governments, and Tribal Governments
are actively pursued.”

In 2015, President Barack Obama named a new leader for the Department of the Interior, Sally Jewell. Just as Obama made a trip to Alaska in late August 2015, Jewell declared the name change official under a law that allows the secretary of the Interior to change a name if the board doesn’t act on the proposal in a “reasonable” amount of time.

“This name change recognizes the sacred status of Denali to many Alaska Natives,” Jewell said. “The name Denali has been official for use by the State of Alaska since 1975, but even more importantly, the mountain has been known as Denali for generations. With our own sense of reverence for this place, we are officially renaming the mountain Denali in recognition of the traditions of Alaska Natives and the strong support of the people of Alaska.”

If someone objects to a name change, they could ask the courts to rule on whether the name change was made legally. Going back to Bde Maka Ska, some people objected to changing the name from Lake Calhoun, so they took the state natural resources agency to court. Eventually, the Minnesota Supreme Court ruled that the name change was done correctly.

Alaska’s two U.S. senators and prominent state figures have strongly objected to Trump’s renaming attempt.

How not to change a place name

Renaming the Gulf of Mexico is a different kind of case, however, from renaming a geographic place within U.S. borders.

The gulf is not within the territorial U.S. On the coast, the first 12 miles from shore are considered part of that country, but outside of that is international waters.

The Board on Geographic Names could change the name to Gulf of America on official U.S. maps, but there is no international board in charge of place names. Each country decides what to call places. And there is no official way for the U.S. to make other countries change the name.

It’s possible that the U.S. could formally ask other countries to change the name, or even impose sanctions against countries that don’t comply.

If the names were officially changed in the U.S., the government would use the new names in official documents, signage and maps. As for all the people and companies in the world that make maps, they usually use the official names. But there is nothing that would force them to, if they believed that a certain name is more widely recognized.The Conversation

Innisfree McKinnon, Associate Professor of Geography, University of Wisconsin-Stout

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Trump inherits the Guantánamo prison, complete with 4 ‘forever prisoners’

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theconversation.com – Lisa Hajjar, Professor of Sociology, University of California, Santa Barbara – 2025-01-24 10:57:00

A control tower overlooks the Camp VI detention facility, at Guantánamo Bay Naval Base, Cuba.
AP Photo/Alex Brandon

Lisa Hajjar, University of California, Santa Barbara

President Joe Biden’s record of handling the U.S. military prison at Guantánamo Bay, Cuba, is decidedly mixed. He succeeded in reducing the detainee population he inherited by more than half, but he compounded problems in the military commissions that the Bush administration had invented in the wake of the 9/11 attacks to try people captured in the “war on terror.” Now all the problems at Guantánamo are again President Donald Trump’s.

When Biden took office in 2021, there were 40 prisoners. Today there are 15, the lowest number since the first 20 Muslim men and boys captured in Afghanistan were airlifted to the base on Jan. 11, 2002.

Biden left Trump four people the U.S. will not release but also cannot put on trial – the so-called “forever prisoners.” He also left intact the troubled military commissions system, with three pending criminal cases against a total of six detainees.

In December 2021, former chief military defense attorney Brig. Gen. John Baker testified before the Senate Judiciary Committee: “It is too late in the process for the current military commissions to do justice for anyone. The best that can be hoped for at this point … is to bring this sordid chapter of American history to an end.” Baker made clear that the only viable option is to resolve the cases with plea bargains for the defendants.

Marine Brig. Gen. John Baker tells U.S. senators that there is no opportunity for justice to be done at Guantánamo.

A chance to make progress

There are three cases that have not yet gone to trial – the 9/11 case with four defendants facing charges for their connections with the attacks, the USS Cole bombing in October 2000 with one defendant and the Bali bombing in October 2002 with one defendant.

The 9/11 and USS Cole cases have been stuck in the pretrial phase since Biden was Barack Obama’s vice president. In the summer of 2024, a breakthrough in the 9/11 case appeared imminent: Prosecutors and defense lawyers for three of the four defendants reportedly reached plea-bargain agreements. Khalid Sheikh Mohammad – the alleged “mastermind” of the attacks – Walid bin Attash and Mustafa Hawsawi agreed to plead guilty and accept life sentences in exchange for the government taking the death penalty off the table. There was no deal for the fourth 9/11 defendant, Ammar al-Baluchi.

The deals were approved on July 31 by the top military officer overseeing the Guantánamo commissions, retired Brig. Gen. Susan Escallier. But two days later, Biden’s defense secretary, Lloyd Austin, stepped into the process and overrode Escallier – whom he had appointed. Austin announced that the plea deals were revoked.

The judge, Air Force Col. Matthew McCall, decided to schedule plea hearings for early January. But after some legal back-and-forth that forced a stay, he had to cancel them. Biden left the case against three 9/11 defendants in limbo.

A beige one-story building with a sign above the door.
The basement of this government building in Bucharest, Romania, held a secret CIA prison, one of many across the world.
AP Photo

Witness to the transition

In mid-January 2025, I made my sixteenth reporting trip to Guantánamo. I came for closing arguments on a motion in the 9/11 case that seeks to suppress statements that Ammar al-Baluchi made to the FBI in January 2007. That was four months after he and 13 others were transferred to Guantánamo from CIA black sites where they were held for years. The litigation to suppress those statements started in 2019.

In Chapter 10 of my book, “The War in Court: Inside the Long Fight against Torture,” I detail how the litigation on this suppression motion made public previously unknown details and under-acknowledged horrors of the CIA’s rendition, detention and interrogation program.

These closing arguments were the culmination of six years of litigation on the key question in the 9/11 case: Does torture matter in the pursuit of justice in the military commissions?

A figure strapped to a table has water poured on its face.
A drawing by Guantánamo detainee Abu Zubaydah depicts a person being waterboarded.
Copyright Abu Zubaydah 2019. Licensed by Professor Mark Denbeaux, Seton Hall Law School

Can Guantánamo be closed?

Of the 780 people ever detained at Guantánamo, 540 were released during the presidency of George W. Bush, who established the detention facility. Obama, who signed an executive order on his second day in office pledging to close Guantánamo within a year, released 200.

In his first term, Trump pledged to keep the facility open. The only man to leave Guantánamo during Trump’s first term was Ahmed al-Darbi, who was repatriated to Saudi Arabia in 2018 to serve out the remainder of his sentence from a 2014 plea bargain agreement.

When Biden took office, he said that he supported shutting down the military prison at Guantánamo. In the early years of his presidency, there was a slow stream of transfers, mostly people who had been cleared for release long ago and were freed.

In Biden’s last months, the pace of transfers quickened. In December 2024, a Kenyan detainee, two Malaysian members of al-Qaida who had pled guilty the previous January, and a Tunisian man who had been in Guantánamo since the day the facility was opened were all repatriated to their countries of origin and freed. In January 2024, 11 Yemenis were transported from the prison to Oman to be resettled.

15 men left behind

The Biden administration had also planned to repatriate a severely disabled Iraqi detainee, Abd al-Hadi al-Iraqi, to serve out his plea-bargained sentence in a Baghdad prison. But a federal judge blocked that transfer, ruling that al-Iraqi would not get necessary medical treatment in Iraq and might be subject to abuse there.

Al-Iraqi is one of the 15 that Biden left behind. Three of them – a Libyan, a Somali and a stateless Rohingya – have long been cleared for release. Their continuing detention without charges highlights a key element of the Guantánamo problem: No one can be released unless the U.S. government finds another country willing to accept them.

One of the remaining detainees, Ali Bahlul, is serving a life sentence for conspiracy to commit war crimes. Six others, including the four 9/11 defendants, are awaiting their trials.

There are also four detainees whom the government refuses to transfer but cannot put on trial for lack of evidence.

A man wearing a beard, mustache and glasses.
The U.S. goverment says it cannot release Abu Zubaydah from Guantánamo because he would disclose classified interrogation techniques critics have labeled torture.
U.S. Central Command via AP

These so-called “forever prisoners” include Abu Zubaydah, a Saudi-born man of Palestinian descent who was taken into CIA custody in 2002 and was used as the guinea pig for the CIA torture program. The government long ago conceded that Abu Zubaydah was not a top leader of al-Qaida – in fact he was not even a member. But he will not be released because he knows how he was treated by the CIA, and that treatment remains highly classified.

The newest forever prisoner is one of the original 9/11 defendants, Ramzi bin al-Shibh; in September 2023, he was declared mentally incompetent to stand trial. Now he is uncharged, unreleased and untreated for his psychological maladies that were caused by the torture he endured in CIA black sites.

The ‘War on Terror’ is not over

When Biden pulled U.S. troops out of Afghanistan in August 2021, he claimed to have ended America’s longest war – and repeated this claim in a January 2025 speech. But the Guantánamo prison remains open, and as long as it is, the “war on terror,” which first put U.S. troops in Afghanistan in 2001, is not over.

How Trump will deal with Guantánamo is an open question. If he focuses on the death penalty, he will press ahead with military commission trials like his predecessors, hoping for unanimous guilty verdicts and death sentences. If he prioritizes cutting wasteful government spending, he will release additional detainees and allow the three plea bargain agreements to go into effect.

No one I spoke to during my last trip was willing to predict what a second Trump term might bode for Guantánamo – except that it won’t be closed.The Conversation

Lisa Hajjar, Professor of Sociology, University of California, Santa Barbara

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Newly discovered photos of Nazi deportations show Jewish victims as they were last seen alive

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theconversation.com – Wolf Gruner, Professor of History, USC Dornsife College of Letters, Arts and Sciences – 2025-01-24 07:43:00

Deportation of Jews in Bielefeld, Germany, on Dec. 13, 1941.
Courtesy City Archive Bielefeld, CC BY-SA

Wolf Gruner, USC Dornsife College of Letters, Arts and Sciences

The Holocaust was the first mass atrocity to be heavily photographed.

The mass production and distribution of cameras in the 1930s and 1940s enabled Nazi officials and ordinary people to widely document Germany’s persecution of Jews and other religious and ethnic minorities.

I co-direct an international research project to collect every available image documenting Nazi mass deportations of Jews, Roma and Sinti, as well as euthanasia victims, in Nazi Germany between 1938 and 1945. The most recently discovered series of images will be unveiled on Jan. 27, 2025 – Holocaust Remembrance Day.

In most cases, these are the very last pictures taken of Holocaust victims before they were deported and perished. That fact gives the project its name, #LastSeen.

A few of the images we’ve tracked down were taken by Jewish people, not Nazi officials, offering a rare glimpse of Nazi mass deportations from a victim’s perspective. As descendants of survivors help our researchers identify the deportees in these images and tell their stories, we give previously faceless victims a voice.

Large group of people wearing Jewish stars gather outdoors, carrying bundles of their belongings
Jewish Germans assemble for deportation in Breslau, Germany, in November 1941.
Courtesy of Regional Association of Jewish Communities in Saxony, Germany, CC BY-SA

A growing archive

The #LastSeen project is a collaboration between several German academic and educational institutions and the USC Dornsife Center for Advanced Genocide Research in the United States. When it began in late 2021, researchers knew of a few dozen deportation images of Jews from 27 German towns that had been gathered for a 2011-2012 exhibition in Berlin.

After contacting 1,700 public and private archives in Germany and worldwide to find more, #LastSeen has now collected visual evidence from 60 cities and towns in Nazi Germany. Of these, we’ve analyzed 36 series containing over 420 images, including dozens of never-before-seen photo series from 20 towns.

Most photographs of Nazi mass deportations from local archives published in our digital atlas were taken by the perpetrators, who documented the event for the police or municipality. That has heavily shaped our visual understanding of these crimes, because they display victims as a faceless mass. When individuals were depicted, it was most often through an antisemitic lens.

A screenshot of the LastSeen digital atlas shows locations of deportations where visual documentation has been uncovered.
The LastSeen digital atlas shows locations of deportations where visual documentation has been uncovered.
Screenshot, LastSeen, CC BY-SA

We have, however, obtained a handful of images taken from a victim’s perspective. In January 2024, the #LastSeen team shared newly discovered photographs showing the Nazi deportations in what was then Breslau, Germany – today Wroclaw, Poland.

They were sent to us for analysis by Steffen Heidrich, a staff member of the Regional Association of Jewish Communities in Saxony, Germany, who came across an envelope titled “miscellaneous” while reorganizing his archive. It contained 13 deportation photographs – the last images taken of dozens of Jewish victims before they were transported from Breslau to Nazi-occupied Lithuania and massacred in November 1941.

Jewish resistance

Many of these pictures in this series show a large, mixed age group of men and women wearing the yellow star – the notorious Nazi-mandated sign for Jews – gathering outside with bundles of their belongings. Some are taken from a peculiar angle, from behind a tree or a wall, suggesting they were snapped clandestinely.

Black-and-white image of a group of people, partially blocked by a tree
People waiting for deportation in Breslau in November 1941.
Courtesy of Regional Association of Jewish Communities in Saxony, Germany, CC BY-SA

Given the deportation assembly point for the Breslau Jews, a guarded local beer garden, our researchers knew that only a person with permission to access that property could have shot these pictures.

For these two reasons, we concluded that an employee of the Jewish community of Breslau must have documented the Nazi crimes – most likely Albert Hadda, a Jewish architect and photographer who clandestinely photographed the November 1938 pogrom in Breslau.

Hadda’s marriage to a Christian partially protected him from persecution. Between 1941 and 1943, the city’s Jewish community tasked him with caring for the deportees at the assembly point until their forced removal.

These 13 recently discovered pictures constitute the most comprehensive series illuminating the crime of mass deportations from a victim’s perspective in Nazi Germany. Their unearthing is testimony to the recently rediscovered widespread individual resistance by ordinary Jews who fought Nazi persecution.

Documenting Fulda

Our project has also identified new deportation photos taken in the German town of Fulda in December 1941, during a snowstorm.

Previously, historians knew of only three pictures of this deportation event. Preserved in the city archive, they show the deportees at the Fulda train station during heavy snowfall.

We discovered two new images of the same Nazi deportation, apparently taken by the same photographer, in a videotaped survivor interview in the Visual History Archive of the USC Shoah Foundation in Los Angeles.

In 1996, the Shoah Foundation interviewed Miriam Berline, née Gottlieb, the daughter of a successful Orthodox Jewish merchant in Fulda. At the end of the two-hour interview, Berline held two photographs up to the camera. They clearly show the same snowy deportation in Fulda.

Black and white photo of Jewish people with their belongings boarding a train in heavy snowfall
Screenshot from Miriam Berline’s interview about the Fulda deportations.
USC Shoah Foundation Visual History Archive, CC BY-SA

Berline, born in 1925, escaped Nazi Germany in 1939. She did not remember how her family obtained the images but recalled the photographer as Otto Weissbach, a “wonderful” man who had helped Fulda’s Jewish families.

Our researchers investigated and learned his name was Arthur Weissbach, a non-Jewish neighbor of the Gottliebs. The factory he owned still exists. Descendants of Jewish families have since confirmed that he kept valuables for them and took care of elderly relatives who stayed behind.

Weissbach’s niece said he was a passionate hobby photographer. Since Weissbach kept contact with survivors after the war, he might have given the images to the Gottlieb family. Today, the family’s copies are lost, but their existence is preserved in Berline’s video interview at the USC Shoah Foundation.

The pictures show the Jews at the Fulda train station on Dec. 8, 1941 – revealing how Nazi deportations happened in plain view.

The day before, Jewish men and women from around Fulda had been summoned and spent the night at a local school gym. In the morning, they were taken to the train station and forced by police to board a train to Kassel, in central Germany, and then eastward onto Riga, in Nazi-occupied Latvia.

In total, 1,031 Jews were deported from Kassel to Riga. Only 12 from Fulda survived.

Identifying the deportation victims

It is difficult to identify the people in the photos we discover. So far, we’ve published 279 biographies in the digital atlas.

In the future, artificial intelligence may help us identify more people from the photos in our collection. But for now, this process takes exhaustive research with the help of local researchers and descendants of survivors, whose names are known from archived transport lists.

Families often struggle to recognize individuals in these images, but sometimes they have family photos that help us do so.

Take, for example, this posed family portrait of two young girls. They are Susanne and Tamara Cohn.

Two little girls pose for a photo
Susanne and Tamara Cohn, circa 1939.
Private Archive, CC BY-SA

Relatives of the Cohn family had this photo. It, along with data from the local Nazi transport list, established that two girls photographed in one of his Breslau deportation shots were the daughters of Willy Cohn.

Cohn, a well-known German-Jewish medieval historian and high school teacher in Breslau, kept a detailed diary about the persecution of the town’s Jews from 1933 to 1941. It was unearthed and published in the 1990s.

This photo, below, may be the last picture ever taken of his children with their mother, Gertrud.

Two little girls walk hand in hand with their mom
Gertrud, Susanne and Tamara Cohn, Breslau, November 1941.
#LastSeen Project, CC BY-SA

New insights

The #LastSeen research project is generating new insights into the history of Nazi mass deportations, new methodologies for photo analysis and new tools for Holocaust education.

In addition to the digital atlas, which has been visited by more than 50,000 people since its launch in 2023, we have developed several award-winning educational tools, including an online game that invites students to search for clues, facts and images of Nazi deportations in an artificial attic.

In workshops for teachers and seminars with students, #LastSeen teaches the history of Nazi deportations and demonstrates how historical photo research works. In Fulda, for example, high schoolers helped us locate the exact places where the photographs were taken.

Those pictures will be published in our atlas on Holocaust Remembrance Day 2025. A public commemoration in Fulda will feature the local students’ contributions.

Depending on fundraising, we hope to extend the #LastSeen project beyond Germany. Collecting images from all 20-plus European countries annexed or occupied by the Nazis will help us better understand these crimes and advance research and education in new ways.

Editor’s note: This article has been updated to correct the date of the Fulda deportations.The Conversation

Wolf Gruner, Professor of History, USC Dornsife College of Letters, Arts and Sciences

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