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Category: quantum physics

How dual-comb spectroscopy works and why it could reshape precision sensing

Spectroscopy has many applications, ranging from fundamental tests of quantum electrodynamics and investigations of molecular structure to environmental sensing, biomedical diagnostics and industrial monitoring. A highly promising spectroscopic instrument that has the potential to transform the field has emerged over the years: the dual-comb spectrometer, which relies on the interference of two mode-locked ultrafast lasers that produce broad frequency combs composed of evenly spaced narrow spectral lines.

A frequency comb is a spectrum of phase-coherent sharp laser lines that are evenly spaced. Such combs based on femtosecond mode-locked lasers, as pioneered at the Max-Planck Institute of Quantum Optics in the 1990s, have revolutionized measurements of frequency and time. In frequency metrology, a laser comb acts as a ruler in frequency space that conveniently links microwave and optical frequencies, and/or measures a large separation between two optical frequencies.

In the past two decades, frequency combs have found new applications. One of them is dual-comb spectroscopy. Dual-comb spectroscopy addresses the challenge of combining wide spectral coverage with high resolution and accuracy by using two optical frequency combs with slightly different repetition frequencies to map optical spectra directly into the radio-frequency domain. The method relies on time-domain interferometry and avoids mechanical scanning, enabling precise, rapid, and broadband measurements. Dual-comb spectroscopy has been implemented across the electromagnetic spectrum, from the terahertz to the visible range, with ongoing efforts towards the ultraviolet range.

These Physicists Claim They Can Send Messages To The Past

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When you try to combine quantum physics with Einstein’s theories, you quickly run into some pretty serious problems. The biggest is that causality – the order in which events occur – becomes uncertain as the rest of quantum physics. A group of physicists have leveraged that uncertainty, and are now claiming that they can send messages to the past using quantum mechanics. It’s not as crazy as it sounds. Let’s take a look.

Paper: https://journals.aps.org/prl/accepted… mugs, posters and more: ➜ https://sabines-store.dashery.com/ 💌 Support me on Donorbox ➜ https://donorbox.org/swtg 👉 Transcript with links to references on Patreon ➜ / sabine 📝 Transcripts and written news on Substack ➜ https://sciencewtg.substack.com/ 📩 Free weekly science newsletter ➜ https://sabinehossenfelder.com/newsle… 👂 Audio only podcast ➜ https://open.spotify.com/show/0MkNfXl… 🔗 Join this channel to get access to perks ➜ / @sabinehossenfelder 📚 Buy my book ➜ https://amzn.to/3HSAWJW #science #sciencenews #physics #quantum In this video, we examine recent headlines suggesting that sending messages into the past has become easier or even possible, drawing from a theoretical physics paper published in a top journal. While these claims might sound like a time machine is within reach, I clarify that this is a theoretical study and not an actual method for backward time travel. It’s crucial for science communication to distinguish between theoretical possibilities in quantum physics and practical applications.

👕T-shirts, mugs, posters and more: ➜ https://sabines-store.dashery.com/
💌 Support me on Donorbox ➜ https://donorbox.org/swtg.
👉 Transcript with links to references on Patreon ➜ / sabine.
📝 Transcripts and written news on Substack ➜ https://sciencewtg.substack.com/
📩 Free weekly science newsletter ➜ https://sabinehossenfelder.com/newsle…
👂 Audio only podcast ➜ https://open.spotify.com/show/0MkNfXl…
🔗 Join this channel to get access to perks ➜
/ @sabinehossenfelder.
📚 Buy my book ➜ https://amzn.to/3HSAWJW

#science #sciencenews #physics #quantum.
In this video, we examine recent headlines suggesting that sending messages into the past has become easier or even possible, drawing from a theoretical physics paper published in a top journal. While these claims might sound like a time machine is within reach, I clarify that this is a theoretical study and not an actual method for backward time travel. It’s crucial for science communication to distinguish between theoretical possibilities in quantum physics and practical applications.

Hume, Rovelli, and why the quantum world contains no objects

Quantum Mechanics is arguably one of the most successful theories in the history of science, for its predictions are confirmed by countless experiments, making it a cornerstone of contemporary physics. However, a century after its inception, the theory still challenges our classical worldview, offering a counterintuitive description of nature at microscopic scales. Contrary to classical mechanics, where objects are individually distinguishable and possess well-defined attributes at all times, QM speaks about indistinguishable systems with indeterminate properties, superposed states, and non-local interactions. Unsurprisingly, then, questions concerning its ontology, i.e., what fundamentally exists, are still vividly discussed to this day.

Despite its empirical success, however, physicists and philosophers alike enquire whether QM should be considered a true description of the natural world, because this theory is affected by conceptual conundrums and formal difficulties (e.g., the measurement problem). To address such issues, new quantum interpretations emerged from the 1950s. Among the many existing alternatives, here we consider a widely discussed framework that turns thirty this year, Carlo Rovelli’s Relational Quantum Mechanics (RQM).

RQM is motivated by Rovelli’s work in loop quantum gravity, where spacetime is not a substance existing per se, but rather it emerges from a dynamic network of relations, providing a relational perspective of it.

Scientists discover atoms suddenly spinning backward in quantum experiment

Scientists have directly watched angular momentum move through a crystal for the very first time — and discovered a bizarre twist along the way. Using ultra-powerful terahertz laser pulses, researchers triggered tiny atomic rotations inside a quantum material and found that the direction of rotation can unexpectedly flip as momentum is transferred. The strange reversal happens because of the crystal’s underlying symmetry, creating an almost impossible-sounding effect where two rotations combine into one spinning the opposite way.

Hydrogen puts quantum wormhole conjecture to the test

A new Physical Review Letters study places constraints on the ER = EPR conjecture, showing that under the authors’ assumptions, the conjecture would imply possible alterations to the hyperfine structure and effective charge of the hydrogen atom—effects that have never been observed.

In 1935, Einstein co-authored two distinct papers. The first proposes the Einstein-Podolsky-Rosen (EPR) paradox describing the quantum entanglement of particles. The second one introduces Einstein-Rosen (ER) bridges connecting distant regions of spacetime, which we today call wormholes.

Nearly a century later, in 2013, physicists Juan Maldacena and Leonard Susskind proposed the ER = EPR conjecture, proposing a link between quantum entanglement and wormholes. This links entanglement, a cornerstone of quantum mechanics, with spacetime connectivity, general relativity. This remains one of the major open questions in modern physics.

‘Butterfly’ molecule spotted at last, completing a 20-year quantum zoo hunt

For two decades, physicists have predicted the existence of a remarkable family of exotic molecules: giant atoms bound to ordinary atoms, with an electron so distant from its nucleus that it sculpts the pair into bizarre and diverse shapes. Reported in Physical Review Letters, the final member of this “quantum zoo” has been spotted. Led by Herwig Ott at RPTU University Kaiserslautern-Landau in Germany, a team of physicists has created and detected the “butterfly” molecule, completing a 20-year hunt for the elusive structure.

The molecules in this quantum zoo belong to a class known as ultralong-range Rydberg molecules. They form when an ordinary atom becomes bound to a Rydberg atom, whose outermost electron has been excited so far from the nucleus that the atom swells to thousands of times its normal size.

The orbital shapes traced out by these distant electrons give each molecule type its character, and its nickname. Some have elaborate lobed structures reminiscent of trilobites; others spread into the winged outline of a butterfly. These molecules are thousands of times more sensitive to electric fields than ordinary molecules, making them especially useful objects for probing the quantum world.

New three‑dimensional magnetic structure discovered with laser light

Flashes of femtosecond laser light, lasting just a few trillionths of a second, have made it possible to observe new magnetic structures for the first time. By using light as a remote control, researchers were able to switch magnetism into previously unseen three-dimensional states at the nanoscale.

Magnetism is often imagined as something simple, pointing in one direction or another. At very small scales, however, magnetism can behave in far more complex ways. Magnetism originates from a quantum property of electrons known as spin, which can be thought of as a tiny internal compass carried by each electron. When many spins interact inside a solid material, they can organize into stable patterns.

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