Lifeboat Foundation

Bouncing cosmology from nonlinear dark energy with two cosmological constants.

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A new mechanism that gives rise to superconductivity in a material where the speed of electrons is almost zero has been discovered by scientists at The University of Texas at Dallas and their partners at The Ohio State University. This breakthrough could pave the way for the development of novel superconductors.

The results of their study, which was recently published in the journal Nature, describe a novel approach to calculate electron speed. This study also represents the first instance where quantum geometry has been recognized as the primary contributing mechanism to superconductivity in any material.

The material the researchers studied is twisted bilayer graphene.

In 2022, two teams made photons act as if time were simultaneously flowing in both directions, which could point to a way to boost quantum devices.

A world of levitating trains, quantum computers and massive energy savings may have come a little closer, after scientists claimed to have attained a long hoped-for dream of physics: room temperature superconductivity.

However, the achievement, announced in the prestigious journal Nature, came with two caveats. The first is that at present it only works at 10,000 times atmospheric pressure. The second is that the last time members of the same team announced similar findings they had to retract them amid allegations of malpractice.

Jorge Hirsch, from the University of California, San Diego, said that on the face of it the achievement was stunning. “If this is real it’s extremely impressive, groundbreaking and worthy of the Nobel prize,” he said. But, he added, “I do not.

To keep his Universe static, Einstein added a term into the equations of general relativity, one he initially dubbed a negative pressure. It soon became known as the cosmological constant. Mathematics allowed the concept, but it had absolutely no justification from physics, no matter how hard Einstein and others tried to find one. The cosmological constant clearly detracted from the formal beauty and simplicity of Einstein’s original equations of 1915, which achieved so much without any need for arbitrary constants or additional assumptions. It amounted to a cosmic repulsion chosen to precisely balance the tendency of matter to collapse on itself. In modern parlance we call this fine tuning, and in physics it is usually frowned upon.

Einstein knew that the only reason for his cosmological constant to exist was to secure a static and stable finite Universe. He wanted this kind of Universe, and he did not want to look much further. Quietly hiding in his equations, though, was another model for the Universe, one with an expanding geometry. In 1922, the Russian physicist Alexander Friedmann would find this solution. As for Einstein, it was only in 1931, after visiting Hubble in California, that he accepted cosmic expansion and discarded at long last his vision of a static Cosmos.

Einstein’s equations provided a much richer Universe than the one Einstein himself had originally imagined. But like the mythic phoenix, the cosmological constant refuses to go away. Nowadays it is back in full force, as we will see in a future article.

“Measuring tBLG devices: the cryostat insert used in the experiments. (Courtesy: J Lau)” Measuring tB.

Measuring time might not seem like that complex of a thing. After all, we rely on simply counting seconds between the “then” and the “now.” But when you really start to break time down to the quantum level, things begin to get a bit foggier.

Self-testing is a promising method to infer the physics underlying specific quantum experiments using only collected measurements. While this method can be used to examine bipartite pure entangled states, so far it could only be applied to limited kinds of quantum states involving an arbitrary number of systems.

Researchers at Sorbonne University, ICFO-Institute of Photonic Sciences and Quantinuum recently introduced a framework for the quantum network-assisted self-testing of all pure entangled states of an arbitrary number of systems. Their paper, published in Nature Physics, could inform future research efforts aimed at certifying quantum phenomena.

“I was a postdoctoral researcher in Barcelona in 2014 in the group of Antonio Acín when the first author, Ivan Šupić and I began working on self-testing quantum states together,” Matty Hoban, one of the researchers who carried out the study, told Phys.org. “That is, certifying that you have systems in particular quantum states without trusting the devices and treating them as black boxes (called the device-independent setting). Part of this work involved exploring different kinds of scenarios of trust.”

Quantum processors are computing systems that process information and perform computations by exploiting quantum mechanical phenomena. These systems could significantly outperform conventional processors on certain tasks, both in terms of speed and computational capabilities.

While engineers have developed several promising quantum computing systems over the past decade or so, scaling these systems and ensuring that they can be deployed on a large-scale remains an ongoing challenge. One proposed strategy to increase the scalability of quantum processors entails the creation of modular systems containing multiple smaller quantum modules, which can be individually calibrated and then arranged into a bigger architecture. This, however, would require suitable and effective interconnects (i.e., devices for connecting these smaller modules).

Researchers at the Southern University of Science and Technology, the International Quantum Academy and other institutes in China have recently developed low-loss interconnects for linking the individual modules in modular superconducting quantum processors. These interconnects, introduced in Nature Electronics, are based on pure aluminum cables and on-chip impendence transformers.