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We probably think we know gravity pretty well. After all, we have more conscious experience with this fundamental force than with any of the others (electromagnetism and the weak and strong nuclear forces). But even though physicists have been studying gravity for hundreds of years, it remains a source of mystery.

In our video Why Is Gravity Different? We explore why this force is so perplexing and why it remains difficult to understand how Einstein’s general theory of relativity (which covers gravity) fits together with quantum mechanics.

Continue reading “To Understand Gravity, Toss a Hard Drive into a Black Hole” »

The ability to cancel magnetic fields has benefits in quantum technology, biomedicine, and neurology.

A team of scientists including two physicists at the University of Sussex has found a way to circumvent a 178-year old theory which means they can effectively cancel magnetic fields at a distance. They are the first to be able to do so in a way that has practical benefits.

The work is hoped to have a wide variety of applications. For example, patients with neurological disorders such as Alzheimer’s or Parkinson’s might in the future receive a more accurate diagnosis. With the ability to cancel out ‘noisy’ external magnetic fields, doctors using magnetic field scanners will be able to see more accurately what is happening in the brain.

Researchers at MIT and the University of Waterloo have developed a high-power, portable version of a device called a quantum cascade laser, which can generate terahertz radiation outside of a laboratory setting. The laser could potentially be used in applications such as pinpointing skin cancer and detecting hidden explosives.

Until now, generation of terahertz radiation powerful enough to perform real-time imaging and fast spectral measurements required temperatures far below 200 Kelvin (−100 degrees Fahrenheit) or lower. These temperatures could only be achieved with bulky equipment that limited the technology’s use to a laboratory setting. In a paper published in Nature Photonics, MIT Distinguished Professor of Electrical Engineering and Computer Sciences Qing Hu and his colleagues report that their terahertz quantum cascade laser can function at temperatures of up to 250 K (−10 degrees Fahrenheit), meaning that only a compact portable cooler is required.

Terahertz quantum cascade lasers, tiny chip-embedded semiconductor laser devices, were first invented in 2002, but adapting them to operate far above 200 K proved to be so difficult that many people in the field speculated that there was a fundamental physical reason preventing it, Hu says.

In 1973, physicist and later Nobel laureate Philip W. Anderson proposed a bizarre state of matter: the quantum spin liquid (QSL). Unlike the everyday liquids we know, the QSL actually has to do with magnetism—and magnetism has to do with spin.

Disordered electron spin produces QSLs

What makes a magnet? It was a long-lasting mystery, but today we finally know that magnetism arises from a peculiar property of sub-atomic particles, like electrons. That property is called “spin,” and the best—yet grossly insufficient—way to think of it is like a child’s spinning-top toy.

Another argument for government to bring AI into its quantum computing program is the fact that the United States is a world leader in the development of computer intelligence. Congress is close to passing the AI in Government Act, which would encourage all federal agencies to identify areas where artificial intelligences could be deployed. And government partners like Google are making some amazing strides in AI, even creating a computer intelligence that can easily pass a Turing test over the phone by seeming like a normal human, no matter who it’s talking with. It would probably be relatively easy for Google to merge some of its AI development with its quantum efforts.

The other aspect that makes merging quantum computing with AI so interesting is that the AI could probably help to reduce some of the so-called noise of the quantum results. I’ve always said that the way forward for quantum computing right now is by pairing a quantum machine with a traditional supercomputer. The quantum computer could return results like it always does, with the correct outcome muddled in with a lot of wrong answers, and then humans would program a traditional supercomputer to help eliminate the erroneous results. The problem with that approach is that it’s fairly labor intensive, and you still have the bottleneck of having to run results through a normal computing infrastructure. It would be a lot faster than giving the entire problem to the supercomputer because you are only fact-checking a limited number of results paired down by the quantum machine, but it would still have to work on each of them one at a time.

Continue reading “Will Quantum Computing Supercharge Artificial Intelligence?” »

Borrowing a page from high-energy physics and astronomy textbooks, a team of physicists and computer scientists at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) has successfully adapted and applied a common error-reduction technique to the field of quantum computing.

In the world of subatomic particles and giant particle detectors, and distant galaxies and giant telescopes, scientists have learned to live, and to work, with uncertainty. They are often trying to tease out ultra-rare particle interactions from a massive tangle of other particle interactions and background “noise” that can complicate their hunt, or trying to filter out the effects of atmospheric distortions and interstellar dust to improve the resolution of astronomical imaging.

Also, inherent problems with detectors, such as with their ability to record all particle interactions or to exactly measure particles’ energies, can result in data getting misread by the electronics they are connected to, so scientists need to design complex filters, in the form of computer algorithms, to reduce the margin of error and return the most accurate results.

Military observers said the disruptive technologies – those that fundamentally change the status quo – might include such things as sixth-generation fighters, high-energy weapons like laser and rail guns, quantum radar and communications systems, new stealth materials, autonomous combat robots, orbital spacecraft, and biological technologies such as prosthetics and powered exoskeletons.

Speeding up the development of ‘strategic forward-looking disruptive technologies’ is a focus of the country’s latest five-year plan.

The first quantum revolution brought about semiconductor electronics, the laser and finally the internet. The coming, second quantum revolution promises spy-proof communication, extremely precise quantum sensors and quantum computers for previously unsolvable computing tasks. But this revolution is still in its infancy. A central research object is the interface between local quantum devices and light quanta that enable the remote transmission of highly sensitive quantum information. The Otto-Hahn group “Quantum Networks” at the Max-Planck-Institute of Quantum Optics in Garching is researching such a “quantum modem”. The team has now achieved a first breakthrough in a relatively simple but highly efficient technology that can be integrated into existing fiber optic networks. The work is published this week in Physical Review X.

The Corona pandemic is a daily reminder of how important the internet has become. The World Wide Web, once a by-product of basic physical research, has radically changed our culture. Could a quantum internet become the next major innovation out of physics?

It is still too early to answer that question, but basic research is already working on the quantum internet. Many applications will be more specialized and less sensual than video conferencing, but the importance of absolutely spy-proof long-distance communication is understandable to everyone. “In the future, a quantum internet could be used to connect quantum computers located in different places,” Andreas Reiserer says, “which would considerably increase their computing power!” The physicist heads the independent Otto-Hahn research group “Quantum Networks” at the Max-Planck-Institute of Quantum Optics in Garching.