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Category: quantum physics – Page 342

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.

Electronic pathways may enhance collective atomic vibrations’ magnetism

Materials with enhanced thermal conductivity are critical for the development of advanced devices to support applications in communications, clean energy and aerospace. But in order to engineer materials with this property, scientists need to understand how phonons, or quantum units of the vibration of atoms, behave in a particular substance.

“Phonons are quite important for studying new because they govern several such as thermal conductivity and carrier properties,” said Fuyang Tay, a graduate student in applied physics working with the Rice Advanced Magnet with Broadband Optics (RAMBO), a tabletop spectrometer in Junichiro Kono’s laboratory at Rice University. “For example, it is widely accepted that superconductivity arises from electron–phonon interactions.

Recently, there has been growing interest in the carried by phonon modes that show circular motion, also known as chiral . But the mechanisms that can lead to a large phonon magnetic moment are not well understood.

Scientists just built a massive 1,000-qubit quantum chip, but why are they more excited about one 10 times smaller?

The company announces its latest huge chip — but will now focus on developing smaller chips with a fresh approach to ‘error correction’

The second-largest quantum computing chip won’t be fitted into IBM’s next-generation System Two quantum computer. Instead, it will use three smaller 133-qubit chips with a much lower error rate.

Physicists Discover Surprising Quantum-Like Behavior in Tiny Bouncing Droplets

Quantum physics is fundamentally weird, so much so that we need thought experiments of hidden cats in boxes and metaphors of spinning coins to even begin to comprehend its laws.

Yet even in our classical world, where physics is more intuitive, shades of quantum behavior can be represented using relatively simple scenarios.

Researchers experimenting with tiny droplets of oil running down two adjacent channels in a bath of vibrating fluid have discovered that the behavior of the droplets matches up with a famous quantum thought experiment.