Physicists from research groups at the University of Stuttgart, Saarbrücken, and Dresden conducting an experiment on quantum teleportation (left to right: Tobias Bauer, Marlon Schäfer, Caspar Hopfmann, Stefan Kazmaier, Tim Strobel, Simone Luca Portalupi). Credit: Julian Maisch
Everyday life on the internet is insecure. Hackers can break into bank accounts or steal digital identities. Driven by AI, attacks are becoming increasingly sophisticated. Quantum cryptography promises more effective protection. It makes communication secure against eavesdropping by relying on the laws of quantum physics. However, the path toward a quantum internet is still fraught with technical hurdles.
Researchers at the Institute of Semiconductor Optics and Functional Interfaces (IHFG) at the University of Stuttgart have now made a decisive breakthrough in one of the most technically challenging components, the quantum repeater. They report their results in Nature Communications.
Nanometer-sized semiconductor islands for information transfer
“For the first time worldwide, we have succeeded in transferring quantum information among photons originating from two different quantum dots,” says Prof. Peter Michler, head of the IHFG and deputy spokesperson for the Quantenrepeater.Net (QR.N) research project.
What is the background? Whether WhatsApp or video stream, every digital message consists of zeros and ones. Similarly, this also applies to quantum communication, in which individual light particles serve as carriers of information.
Zero or one is then encoded in two different directions of polarization of the photons (i.e., their orientation in the horizontal and vertical directions or in a superposition of both states). Because photons follow the laws of quantum mechanics, their polarization cannot always be completely read out without leaving traces. Any attempt to intercept the transmission would inevitably be detected.
Making the quantum internet ready for the fiber-optic infrastructure
Another challenge: An affordable quantum internet would use optical fibers—just like today’s internet. However, light has only a limited range. Conventional light signals, therefore, need to be renewed approximately every 50 kilometers using an optical amplifier.
Because quantum information cannot simply be amplified or copied and forwarded, this does not work in the quantum internet. However, quantum physics allows information to be transferred from one photon to another as long as the information stays unknown. This process is referred to as quantum teleportation.
Quantum repeaters as nodes for information transmission
Building on this, physicists are developing quantum repeaters that renew quantum information before it is absorbed in the optical fiber. They are to serve as nodes for the quantum internet. However, there are considerable technical hurdles. To transmit quantum information via teleportation, the photons must be indistinguishable (i.e., they must have approximately the same temporal profile and color). This proves extremely difficult because they are generated at different locations from different sources.
“Light quanta from different quantum dots have never been teleported before because it is so challenging,” says Tim Strobel, scientist at the IHFG and first author of the study. As part of QR.N, his team has developed semiconductor light sources that generate almost identical photons.
“In these semiconductor islands, certain fixed energy levels are present, just like in an atom,” says Strobel. This allows individual photons with defined properties to be generated at the push of a button.
“Our partners at the Leibniz Institute for Solid State and Materials Research in Dresden have developed quantum dots that differ only minimally,” says Strobel. This means that almost identical photons can be generated at two locations.
Information is ‘beamed’ from one photon to another
At the University of Stuttgart, the team succeeded in teleporting the polarization state of a photon originating from one quantum dot to another photon from a second quantum dot. One quantum dot generates a single photon, the other an entangled photon pair.
Entangled means that the two particles constitute a single quantum entity, even when they are physically separated. One of the two particles travels to the second quantum dot and interferes with its light particle. The two overlap. Because of this superposition, the information of the single photon is transferred to the distant partner of the pair.
Instrumental for the success of the experiment were quantum frequency converters, which compensate for residual frequency differences between the photons. These converters were developed by a team led by Prof. Christoph Becher, an expert in quantum optics at Saarland University.
Improvements for reaching considerably greater distances
“Transferring quantum information between photons from different quantum dots is a crucial step toward bridging greater distances,” says Michler.
In the Stuttgart experiment, the quantum dots were separated only by an optical fiber of about 10 m length. “But we are working on achieving considerably greater distances,” says Strobel.
In earlier work, the team had shown that the entanglement of the quantum dot photons remains intact even after a 36-kilometer transmission through the city center of Stuttgart. Another aim is to increase the current success rate of teleportation, which currently stands at just over 70%. Fluctuations in the quantum dot still lead to slight differences in the photons.
“We want to reduce this by advancing semiconductor fabrication techniques,” says Strobel.
“Achieving this experiment has been a long-standing ambition — these results reflect years of scientific dedication and progress,” says Dr. Simone Luca Portalupi, group leader at the IHFG and one of the study coordinators. “It’s exciting to see how experiments focused on fundamental research are taking their first steps toward practical applications.”
LGBTQ+ people are significantly more likely to stopped, harassed, and even falsely accused by the police than non-LGBTQ+ people, according to a new study released by the Williams Institute. As a result, LGBTQ+ people are less likely to contact the police when they need support, the study notes.
“Participants in these studies have described being stopped for no reason, encountering hostile treatment when police discovered they were transgender, and having officers assume they were engaging in sex work or other illegal activities,” the report explains, detailing some of its qualitative research. “Participants in several studies shared that they have concerns related to their LGBTQ identity about contacting the police or that they avoid police in order to avoid negative interactions.”
The Williams Institute study analyzed 25 years of research on interactions between the LGBTQ+ community and police. The data came from surveys, incident reports, government investigations, qualitative research, court cases, and anecdotal reports.
The findings might not be astonishing to those familiar with LGBTQ+ history, most notably the police raids that led to the Stonewall Riots. While decades have passed since crimes explicitly targeted LGBTQ+ social behaviors, the report suggests that changes only run so deep and notes that it was only 2003 when the Supreme Court ruled sodomy laws as unconstitutional.
The Williams Institute study analyzed 25 years of research on interactions between the LGBTQ+ community and police. The data came from surveys, incident reports, government investigations, qualitative research, court cases, and anecdotal reports.
The findings might not be astonishing to those familiar with LGBTQ+ history, most notably the police raids that led to the Stonewall Riots. While decades have passed since crimes explicitly targeted LGBTQ+ social behaviors, the report suggests that changes only run so deep and notes that it was only 2003 when the Supreme Court ruled sodomy laws as unconstitutional.
Just as the censorious Hays Code from the 1930s to ’60s still defines aspects of modern media, past criminalization of LGBTQ+ identities has created an environment where discrimination and harassment are common.
“The history of criminalization and related tensions between law enforcement and LGBTQ communities have legacies that extend to the present day,” the report acknowledges. The authors also note the new waves of anti-trans laws, pointing to the fact that “Recent years have seen a rise in anti-LGBTQ legislation, with many of these new laws imposing criminal penalties.”
The analysis of survey data revealed that as well as being more likely to be stopped, searched, arrested, and held in custody, LGBTQ+ people were also more likely to report verbal, physical, and sexual harassment and assault at the hands of law enforcement.
The study’s lead author, Joshua Arrayales, a law fellow at the Williams Institute, released a statement noting that all of this meant that LGBTQ+ people were less likely to report crimes, and that affects future data.
“Reporting crimes is essential for accurate crime statistics, proper allocation of crime prevention resources, and support services that address the unique needs of LGBTQ survivors,” Arrayales said.
As previous data already suggested that LGBTQ+ people are more likely to be crime victims, this research supports the idea that many crimes against queer people go unreported.
While LGBTQ+ people are more likely to be stopped by police, face harassment, and avoid contacting law enforcement as a result, the statistical differences grow for specific groups. People who are part of other marginalized groups reported higher incidence rates; one study showed that 46% of trans people said they’d avoid contacting the police if they were the victim of a crime.
The study also found that these interactions often had a lasting impact. A “growing body of research” suggests that there are “associations between police violence and harassment and binge drinking, stress, depression, and other negative health outcomes.”
The Williams Institute study also provides action items for improving the current situation: “(1) legal and policy reform, (2) enhanced accountability and representation within law enforcement agencies, (3) community engagement and support, and (4) continuous data collection and evaluation of these initiatives.”
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This was an entirely illegal strike on people in distress who were no longer considered combatants in any way. This is a war crime ordered by Drunken Christian White Nationalist low ranking when got out of the military now head of the Department Of Defense. Hugs
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