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Category: quantum physics

Quantum computers are coming to break our codes faster than anyone expected

Online data is generally pretty secure. Assuming everyone is careful with passwords and other protections, you can think of it as being locked in a vault so strong that even all the world’s supercomputers, working together for 10,000 years, could not crack it.

But last month, Google and others released results suggesting a new kind of computer—a quantum computer—might be able to open the vault with significantly less resources than previously thought.

The changes are coming on two fronts. On one, tech giants such as IBM and Google are racing to build ever-larger quantum computers: IBM hopes to achieve a genuine advantage over classical computers in some special cases this year, and an even more powerful “fault-tolerant” system by 2029.

A tabletop ring of atoms brings the universe’s doomsday vacuum collapse into the lab

Physicists in China have simulated the effect of “false vacuum decay”: a phenomenon believed to play out constantly in the seemingly empty expanses of space, and which one theory even suggests could bring an abrupt end to the entire universe. In a paper published in Physical Review Letters, Yu-Xin Chao and colleagues at Tsinghua University, Beijing, mimicked the effect using a simple tabletop experiment.

For now, quantum field theory is our most accurate framework for fundamental physics below the scale at which gravity becomes important. It predicts that there is no such thing as a perfect vacuum: while a given space may appear entirely empty, the theory suggests that it is actually just the lowest-energy state of a continuous quantum field.

Since a quantum field can possess multiple local minima energy, this means that a seemingly stable local ground state may not be the most stable state possible for the field as a whole—it is simply separated from a lower-energy, more stable state by an energy barrier, much as a valley may be separated from a deeper valley by a high mountain ridge.

A tiny twist and synthetic diamond put superconductivity on a switch, opening a new route to lossless electronics

Researchers have discovered evidence that superconductivity can be controlled by influencing the surrounding environment, a finding that may lead to more efficient electronics down the road, according to a new study published in the journal Nature Physics.

Superconductivity, or the ability of certain materials to conduct electric currents without any energy loss when cooled below a critical temperature, is a property still not very well understood. While a major challenge, understanding more about its formation mechanisms could lead to better, more long-lasting materials as well as more powerful quantum devices.

Quantum sensors get a precision boost as 2D defects reveal their hidden timing

A key factor for the performance of sensors is the speed at which the system returns to its initial state after a disturbance or measurement, similar to the taring of a balance. In the quantum sensor under investigation, this corresponds to the transition of electrons from an energetically excited state to the ground state. However, the electrons remain in a kind of metastable intermediate state for a short time. A team of physicists from Julius-Maximilians-Universität Würzburg (JMU) has now directly measured this waiting time in a two-dimensional material: It lasts exactly 24 billionths of a second.

This knowledge is particularly important for quantum technology. It can be used to significantly increase the accuracy of atomic sensors, paving the way for the medical diagnostics of the future, for example. Professor Vladimir Dyakonov, Head of the Chair of Experimental Physics VI (EPVI), was responsible for the study published in the journal Science Advances.

Unlocking unusual superconductivity in a lightweight element

Superconductors—materials that can conduct electricity without energy loss—are crucial for next-generation high-efficiency, ultrafast electronics. However, most superconductors share a critical limitation: they lose their superconducting properties in strong magnetic fields. In contrast, a class of superconductors containing heavy elements can sustain an unusual type of superconductivity in magnetic fields beyond the conventional limit. Now, new research has demonstrated that this limitation can be overcome by sandwiching atomically thin films of a lightweight element called gallium between two other materials to engineer quantum interactions at the interfaces between the layers.

A paper describing the research, led by an interdisciplinary team at Penn State’s Materials Research Science and Engineering Center (MRSEC) for Nanoscale Science, was published in the journal Nature Materials. The team showed that when just three atomic layers of gallium are layered between graphene and a silicon carbide substrate, the resulting structure maintains superconductivity in magnetic fields that are parallel to the surface of the material, or in-plane, well above the expected limit.

“This discovery highlights the strength of collaborative, cross-disciplinary research fostered by the Penn State MRSEC,” said Cui-Zu Chang, professor of physics at Penn State Eberly College of Science and leader of the research team. “By bringing together expertise in materials synthesis, quantum transport and theoretical modeling, we were able to uncover a phenomenon that would have been difficult to realize within a single research group.”

Physicists discover how reverse to ‘quantum scrambling’

Quantum computers stand to revolutionize research by helping investigators solve certain problems exponentially faster than with conventional computers. Current quantum computers encounter a challenge where they lose stored information in a process known as quantum scrambling. However, scientists at the University of California, Irvine have discovered a method to enable computers to preserve the data that would otherwise be lost during the scrambling process. The research is published in the journal Physical Review Letters.

“My work is on understanding how this scrambling of quantum information works and in understanding how it emerges,” said Thomas Scaffidi, assistant professor of physics and astronomy and lead author of the new study. “We’re trying to determine whether the information is still there in some form and if we can reverse the scrambling process completely.”

The fundamental unit of information in quantum computing is the qubit. Conventional computers use bits, which store information as either a 0 or a 1, while a qubit stores information as either a 0, a 1, or both at the same time.

Record-breaking photonics approach traps light on a chip for millions of cycles

For years, scientists have dreamed of using atomically thin van der Waals (vdW) materials to build faster, more efficient photonic chips. These materials can be stacked and tuned with extraordinary precision, opening possibilities far beyond those of conventional technologies. The challenge is that they are extremely fragile, making them notoriously difficult to shape with standard nanofabrication tools.

Now, an international team of researchers including scientists from Aalto University has overcome this long-standing barrier. By developing a method for what can be described as nanoscale surgery, they were able to sculpt these delicate materials without destroying them, achieving record-breaking performance in the process.

Published in Nature Materials, the work marks an important step forward for vdW materials, shifting them from passive coatings toward becoming the active building blocks of future photonic and quantum devices.

High-resolution imaging captures cavity-induced density waves in a quantum gas

A new study, published in Physical Review Letters, reports that scientists have successfully imaged the formation of cavity-induced density waves induced by laser light in an ultracold quantum gas. Previously, only global signals, such as photon leakage or the peak in energy deposition of a fast charged particle (Bragg peaks), have been used to detect this kind of ordering. Prior to this study, there had been no direct, high-resolution in situ imaging of cavity-induced density-wave order in ultracold gases.

When laser light is arranged so that it bounces back and forth between two mirrors, light waves become trapped and create what is referred to as an optical cavity. This creates standing waves or amplifies light through resonance. When atoms in an ultracold unitary Fermi gas are placed in an optical cavity, they can absorb and emit this light. Unitary Fermi gases exist in a strongly interacting state where the wave scattering length makes interactions independent of the specific atomic details.

Light emitted by atoms in the gas can be absorbed by other atoms. This exchange of photons creates further interactions between the atoms that can cause a self-rearrangement into a periodic pattern within the gas, referred to as a density wave. This self-organization occurs above a critical threshold, called the superradiant phase transition, where the exchange of photons enables simultaneous, collective interaction among all atoms.

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