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Category: quantum physics – Page 335

IBM’s Juan Bernabé-Moreno: ‘Understanding nature using traditional computers is impossible’

Juan Bernabé-Moreno is IBM’s director of research for Ireland and the United Kingdom. The Spanish computer scientist is also responsible for IBM’s climate and sustainability strategy, which is being developed by seven global laboratories using artificial intelligence (AI) and quantum computing. He believes quantum computing is better suited to understanding nature and matter than classical or traditional computers.

Question. Is artificial intelligence a threat to humanity?

Answer. Artificial intelligence can be used to cause harm, but it’s crucial to distinguish between intentional and malicious use of AI, and unintended behavior due to lack of data control or governance rigor.

Study: Physicists create giant trilobite Rydberg molecules

Kaiserslautern physicists in the team of Professor Dr. Herwig Ott have succeeded for the first time in directly observing pure trilobite Rydberg molecules. Particularly interesting is that these molecules have a very peculiar shape, which is reminiscent of trilobite fossils. They also have the largest electric dipole moments of any molecule known so far.

The researchers used a dedicated apparatus that is capable of preparing these fragile at ultralow temperatures. The results reveal their chemical binding mechanisms, which are distinct from all other chemical bonds. The study was published in the journal Nature Communications.

For their experiment, the physicists used a cloud of rubidium that was cooled down in an to about 100 microkelvin—0.0001 degrees above absolute zero. Subsequently, they excited some of these atoms into a so-called Rydberg state using lasers. “In this process, the outermost electron in each case is brought into far-away orbits around the atomic body,” explains Professor Herwig Ott, who researches ultracold quantum gases and quantum atom optics at University of Kaiserslautern-Landau.

‘Teleporting’ images across a network securely using only light

Nature Communications published research by an international team from Wits and ICFO-The Institute of Photonic Sciences, which demonstrates the teleportation-like transport of “patterns” of light—this is the first approach that can transport images across a network without physically sending the image and a crucial step towards realizing a quantum network for high-dimensional entangled states.

Quantum communication over long distances is integral to and has been demonstrated with two-dimensional states (qubits) over very long distances between satellites. This may seem enough if we compare it with its classical counterpart, i.e., sending bits that can be encoded in 1s (signal) and 0s (no signal), one at a time.

However, quantum optics allow us to increase the alphabet and to securely describe more in a single shot, such as a unique fingerprint or a face.

Updating how we measure quantum quality and speed

IBM introduces introducing two new metrics — error per layered gate (EPLG) and CLOPSh — to fully encapsulate the performance of 100+ qubit processors powering this utility-scale era.

Layer fidelity provides a benchmark that encapsulates the entire processor’s ability to run circuits while revealing information about individual qubits, gates, and crosstalk. It expands on a well-established way to benchmark quantum computers, called randomized benchmarking. With randomized benchmarking, we add a set of randomized Clifford group gates (that’s the basic set of gates we use: X, Y, Z, H, SX, CNOT, ECR, CZ, etc.) to the circuit, then run an operation that we know, mathematically, should represent the inverse of the sequence of operations that precede it.

If any of the qubits do not return to their original state by the inverse operation upon measurement, then we know there was an error. We extract a number from this experiment by repeating it multiple times with more and more random gates, plotting on a graph how the errors increase with more gates, fitting an exponential decay to the plot, and using that line to calculate a number between 0 and 1, called the fidelity.

So, layer fidelity gives us a way to combine randomized benchmarking data for larger circuits to tell us things about the whole processor and its subsets of qubits.

Quantum batteries could charge by breaking our understanding of time

Causality is key to our experience of reality: dropping a glass, for example, causes it to smash, so it can’t smash before it’s dropped. But in the quantum world those rules don’t necessarily apply, and scientists have now demonstrated how that weirdness can be harnessed to charge a quantum battery.

In a sense, you could say that quantum batteries are powered by paradoxes. On paper, they work by storing energy in the quantum states of atoms and molecules – but of course, as soon as the word “quantum” enters the conversation you know weird stuff is about to happen. In this case, a new study has found that quantum batteries could work by violating cause-and-effect as we know it.

“Current batteries for low-power devices, such as smartphones or sensors, typically use chemicals such as lithium to store charge, whereas a quantum battery uses microscopic particles like arrays of atoms,” said Yuanbo Chen, an author of the study. “While chemical batteries are governed by classical laws of physics, microscopic particles are quantum in nature, so we have a chance to explore ways of using them that bend or even break our intuitive notions of what takes place at small scales. I’m particularly interested in the way quantum particles can work to violate one of our most fundamental experiences, that of time.”

Scientists measure entanglement at the LHC

Quantum entanglement is the most distinctive signature of quantum mechanics, says Juan R. Muñoz de Nova, a condensed-matter physicist at the Complutense University of Madrid. “It contradicts the intuitions we have on a daily basis,” he says. “That is why entanglement is so intrinsic to quantum mechanics.”

This phenomenon has been observed by researchers around the world, and the 2022 Nobel Prize in physics was awarded to three scientists for experimentally advancing our understanding of it. Scientists have detected quantum entanglement through experiments involving macroscopic diamonds and ultracold gases.

In September 2023, the ATLAS collaboration made another advancement when they unveiled the highest-energy measurement of quantum entanglement ever, using top quarks produced in the Large Hadron Collider at CERN. Interestingly, the measurement turned out a bit differently than expected.

Quantum Teleportation Enters the Real World

Two separate teams of scientists have taken quantum teleportation from the lab into the real world. Researchers working in Calgary, Canada and Hefei, China, used existing fiber optics networks to transmit small units of information across cities via quantum entanglement — Einstein’s “spooky action at a distance.”

According to quantum mechanics, some objects, like photons or electrons, can be entangled. This means that no matter how far apart they are, what happens to one will affect the other instantaneously. To Einstein, this seemed ridiculous, because it entailed information moving faster than the speed of light, something he deemed impossible. But, numerous experiments have shown that entanglement does indeed exist.

The challenge was putting it to use. A few experiments in the lab had previously managed to send information using quantum entanglement. But translating their efforts to the real world, where any number of factors could confound the process is a much more difficult challenge.