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From quantum error correction to emergent gravity: Probing holographic universes at QLab

One of the deepest ambitions in modern physics is understanding how the fabric of space and time could emerge from fundamental quantum degrees of freedom to establish a quantum theory of gravity.

In the new paper, “Observation of gravity-like signatures in holographic codes on a quantum computer,” posted to the arXiv preprint server, researchers from the National Quantum Laboratory (QLab@UMD), the Duke Quantum Center, the Virginia Tech Center for Quantum Information Science and Engineering, Caltech’s Institute for Quantum Information and Matter, IonQ and BlueQubit have successfully simulated toy models of quantum gravity according to the AdS/CFT correspondence. The team, led by Crystal Noel and Charles Cao, includes quantum-computation pioneers John Preskill and Christopher Monroe.

Using the IonQ Forte ion-trap quantum computer, the study implements the intriguing HaPPY quantum error-correction code, which forms a bridge between quantum computing and quantum gravity. This code simulates a highly simplified model of a universe with a negative cosmological constant that features a so-called bulk-boundary correspondence, in which the properties of a higher-dimensional gravitational universe (bulk) are completely determined by a lower-dimensional quantum system without gravity living on the boundary. The team successfully demonstrated fundamental entanglement properties of these systems.

Frozen fiber couples light and sound 1,000 times more strongly than standard glass fibers

Researchers have developed a new type of optical fiber by freezing a glass capillary filled with liquid. It guides light and sound waves simultaneously and enables highly efficient coupling between them. The high coupling strength lowers the energy consumption of photonic neuromorphic computing schemes and quantum signal processing applications by several orders of magnitude.

When volcanoes erupt, one can observe streams of liquid lava cool and solidify into rock formations at the bottoms of volcanoes. The same physical process—a liquid changing into a solid phase upon cooling—can be observed when lakes start freezing during cold winters. These phase changes always come with changes in the physical properties of the material, such as the density or refractive index that govern how sound and light move through it.

This fundamental physical process is also used during the melting of glass preforms to loosen their structure while drawing optical fiber. These fibers then guide light through their cores, allowing the transmission of information via light very quickly over long distances, which is why they are widely used for telecommunications applications.

New radio-burst method helps locate universe’s missing ordinary matter

Stars and galaxies make up much of the universe’s ordinary, observable matter. But for decades, scientists have wrestled with a cosmic conflict: There should be much more.

Physicists have good estimates of how much matter was present in the early universe. Shortly after the Big Bang, roughly 83% of all matter in the universe was composed of invisible dark matter, with ordinary matter making up the rest. And yet, these estimates exceed the amount of ordinary matter seen in stars and galaxies today. Where, then, did all the missing ordinary matter go?

Now MIT scientists, as part of the CHIME/FRB Collaboration, are using far-off radio signals to reveal missing matter in the vast space between galaxies. The team has developed a new method to search out missing matter by combining locations of galaxies with detections of fast radio bursts.

Quantum sensing microscope illuminates transistor design

Artificial intelligence faces an energy crisis stemming from a physical traffic jam inside modern computer chips. Processors must continually shuffle data, such as the billions of parameters in complex models, between separate computing and memory nodes. This traffic jam, known as the “von Neumann bottleneck,” hinders the speed and energy efficiency of advanced processors.

To tackle this problem, scientists are developing spintronics, which leverages the electron’s “spin,” or intrinsic magnetic orientation, for more efficient devices. A long-sought milestone in this field is a single device, known as a “spin transistor,” that combines a magnetic bit with a semiconducting switch, allowing it to compute and store data simultaneously.

“The major challenge is understanding how magnetism and electrical current interact in nanoscale devices,” said Boston College physics professor Brian Zhou, whose group led the study. “We developed a single-spin quantum microscope to observe magnetic states inside atomically thin devices as they actively process electrical information.”

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