Science

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Creating Temporal Light Reflections With Metamaterials

January 1, 2025 by 8 Comments

Owing to the wave nature of light there are many ways that such different waves can interact with each other, but also with materials. Everyone knows about reflecting light with a mirror, which is a property of materials like metals, but specific structures can cause the light to behave in a way that creates rather amazing results.

Examples of this are cases of iridescence in nature (like butterfly wings) and eye color, where the perceived colors are the result of environmental light interacting with these structures rather than pigmentation or dyes. An even more interesting interaction has now been demonstrated by reflecting multiple microwave radiation beams off each other, creating a time reflection.

The study by [Emanuele Galiffi] et al. (shared copy) was published in Nature Physics. By creating a metamaterial that allows for temporal coherent wave control (CWC) the electromagnetic radiation was controlled to where it allowed for this kind of unusual interaction. The key here being that there is no major constructive or destructive interaction between the two waves as with spatial CWC, rather the wave reflect off each other, or more specifically the time interface.

Although the popular reporting talks about ‘turning back time’ and ‘watching the back of your own head in a mirror’, the impact is far less dramatic: in the article conclusion the researchers mention unveiling new light-matter interactions in the microwave- and other parts of the spectrum, as well as new ways to control and shape light.

Top image: Temporal coherent wave control and photonic collisions enabled by time-interfaces. (Credit: Emanuele Galiffi et al., Nature Physics, 2023)

Experimental setup and measured optical depth. (Credit: Josiah Sinclair et al,, PRX Quantum, 2022)

Quantum Mechanics And Negative Time With Photon-Atom Interactions

December 31, 2024 by 8 Comments

Within our comfortable world of causality we expect that reactions always follow an action and not vice versa. This why the recent chatter in the media about researchers having discovered ‘negative time’ with photons being emitted before the sample being hit by source photons created such a stir. Did these researchers truly just crack our fundamental concepts of (quantum) physics wide open? As it turns out, not really.

Much of the confusion stems from the fact that photons aren’t little marbles that bounce around the place, but are an expression of (electromagnetic) energy. This means that their resulting interaction with matter (i.e. groupings of atoms) is significantly more complicated, often resulting in the photonic energy getting absorbed by an atom, boosting the energy state of its electron(s) before possibly being re-emitted as the excited electrons decay into a lower orbit.

This dwell time before re-emission is what is confusing to many, as in our classical understanding we’d expect this to be a very deterministic process, while in a quantum world it most decidedly is not.

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Different potato varieties. – The potato is the vegetable of choice in the United States. On average, Americans devour about 65 kg of them per year. New potato releases by ARS scientists give us even more choices of potatoes to eat. (Credit: Scott Bauer, USDA ARS)

Re-engineering Potatoes To Remove Their All-Natural Toxins

December 30, 2024 by 66 Comments

Family Solanum (nightshade) is generally associated with toxins, and for good reasons, as most of the plants in this family are poisonous. This includes some of everyone’s favorite staple vegetables: potatoes, tomatoes and eggplant, with especially potatoes responsible for many poisonings each year. In the case of harvested potatoes, the chemical responsible (steroidal glycoalkaloids, or SGA) is produced when the potato begins to sprout. Now a team of researchers at the University of California have found a way to silence the production of the responsible protein: GAME15.

The research was published in Science, following earlier research by the Max Planck Institute. The researchers deleted the gene responsible for GAME15 in Solanum nigrum (black nightshade) to confirm that the thus modified plants produced no SGA. In the case of black nightshade there is not a real need to modify them as – like with tomatoes – the very tasty black berries they produce are free of SGA, and you should not eat the SGA-filled and very bitter green berries anyway, but it makes for a good test subject.

Ultimately the main benefits of this research appear to be in enriching our general understanding of these self-toxicity mechanisms of plants, and in making safer potatoes that can be stored without worries about them suddenly becoming toxic to eat.

Top image: Different potato varieties. (Credit: Scott Bauer, USDA ARS)

A Low-Cost Spectrometer Uses Discrete LEDs And Math

December 28, 2024 by 53 Comments

A spectrometer is a pretty common lab instrument, useful for determining the absorbance of a sample across a spectrum of light. The standard design is simple; a prism or diffraction grating to break up a light source into a spectrum and a detector to measure light intensity. Shine the light through your sample, scan through the spectrum, and graph the results. Pretty easy.

That’s not the only way to do it, though, as [Markus Bindhammer] shows with this proof-of-concept UV/visible spectrometer. Rather than a single light source, [Marb] uses six discrete LEDs, each with a different wavelength. The almost-a-rainbow’s-worth of LEDs are mounted on circular PCB, which is mounted to a stepper motor through a gear train. This allows the instrument to scan through all six colors, shining each on the sample one at a time. On the other side of the flow-through sample cuvette is an AS7341 10-channel color sensor, which can measure almost the entire spectrum from UV to IR.

The one place where this design seems iffy is that the light source spectrum isn’t continuous, as it would be in a more traditional design. But [Marb] has an answer for that; after gathering data at each wavelength, he applies a cubic spline interpolation to derive the spectrum. It’s demonstrated in the video below using chlorophyll extracted from spinach leaves, and it seems to generate a reasonable spectrum. We suppose this might miss a narrow absorbance spike, but perhaps this could be mitigated by adding a few more LEDs to the color wheel.

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Experimental sequence for the Ramsey-type phonon anharmonicity measurement. (Credit: Yu Yang et al., Science, 2024)

Creating A Mechanical Qubit That Lasts Longer Than Other Qubits

December 27, 2024 by No comments

Among the current challenges with creating quantum computers is that the timespan that a singular qubit remains coherent is quite limited, restricting their usefulness. Usually such qubits consist of an electromagnetic resonator (boson), which have the advantage of possessing discrete energy states that lend themselves well to the anharmonicity required for qubits. Using mechanical resonators would be beneficial due to the generally slower decoherence rate, but these have oscillations (phonons) that are harmonic in nature. Now researchers may have found a way to use both electromagnetic qubits and mechanical resonators to create a hybrid form that acts like a mechanical qubit, with quite long (200 µs) coherence time.

As per the research paper by [Yu Yang] and colleagues in Science (open access preprint), their experimental mechanical qubit (piezoelectric disc and superconducting qubit on sapphire) was able to be initialized and read out, with single-qubit gates demonstrated. The experimental sequence for the phonon anharmonicity measurement is shown in the above image (figure 2 in the paper), including the iSWAP operations which initialize the hybrid qubit. Effectively this demonstrates the viability of such a hybrid, mechanical qubit, even if this experimental version is not impressive yet compared to the best electromagnetic qubit. Those have managed to hit a coherence time of 1 ms.

The lead researcher, [Yu Yang] expresses his confidence that they can improve this coherence time with more optimized designs and materials, with future experiments likely to involve more complex quantum gates as well as sensor designs.

Taking “Movies” Of Light In Flight

December 25, 2024 by 10 Comments

This one isn’t clickbait, but it is cheating. [Brian Haidet], the guy behind Alpha Phoenix, has managed to assemble movie footage of a laser beam crossing his garage, using a rig he put together for just a few hundred dollars. How, you ask? Well, for the long version, you’re going to want to watch the video, also embedded below. But we’ll give you the short version here.

Light travels about a foot in a nanosecond. What have you got that measures signals on a nanosecond scale pretty reliably? Of course, it’s your oscilloscope. The rest of [Brian]’s setup includes a laser that can pull off nanosecond pulses, a sensor with a nanosecond-ish rise time, and optics that collect the light over a very small field of view.

He then scans the effective “pinhole” across his garage, emitting a laser pulse and recording the brightness over time on the oscilloscope for each position. Repeating this many thousands of times and putting them all together relative to the beginning of each laser pulse results in a composite movie with the brightness at each location resolved accurately enough to watch the light beam fly. Or to watch different time-slices of thousands of beams fly, but as long as they’re all the same, there’s no real difference.

Of course, this isn’t simple. The laser driver needs to push many amps to get a fast enough rise time, and the only sensor that’s fast enough to not smear the signal is a photomultiplier tube. But persistence pays off, and the results are pretty incredible for something that you could actually do in your garage.

Photomultiplier tubes are pretty damn cool, and can not only detect very short light events, but also very weak ones, down to a single photon. Indeed, they’re cool enough that if you get yourself a few hundred thousand of them and put them in a dark place, you’re on your way to a neutrino detector.  Continue reading “Taking “Movies” Of Light In Flight” →

Close up of a Dutch etymology dictionary showing Esperanto, and a candle

Esperanto: The Language That Hoped To Unite The World

December 25, 2024 by 63 Comments

Christmas: a good time to broach a topic of hope. We’re talking Esperanto. This language that spurred the hope it one day could hack the barriers between people, eliminating war and miscommunication. The video below unpacks the history of this linguistic marvel. Esperanto was a constructed language dreamed up in 1887 by Ludwik Zamenhof, a Polish-Russian eye doctor with a knack for linguistics and great ideals. If you’re a little into linguistics yourself, you’ll sure know the name stems from the Latin sperare: to hope.

Inspired by the chaos of multilingual strife in his hometown, Zamenhof created Esperanto to unite humanity under a single, simple, easy-to-learn tongue. With just 16 grammar rules, modular word-building, and no pesky exceptions — looking at you, English — Esperanto was a linguistic hack ahead of its time.

But Esperanto wasn’t just a novelty—it almost became the lingua franca of diplomacy. In 1920, Iran proposed Esperanto as the official language of the League of Nations, but the French vetoed it, fearing their language’s global dominance was at risk. From there, Esperanto’s journey took a darker turn as both Nazi Germany and Stalinist Russia persecuted its speakers. Despite this, Esperanto persisted, surfacing in quirky corners of culture, from William Shatner’s Esperanto-only horror film Incubus to its inclusion on NASA’s Voyager Golden Record.

Fast-forward to the digital age: Esperanto is thriving on online learning platforms, where over a million learners explore its minimalist elegance. It appears at places in various editions of Grand Theft Auto. It has even inspired modern makers to create new constructed languages, like Loglan, Toki Pona, and even Klingon. Could Esperanto—or any reimagined language—rise again to unite us? For curious minds, watch the video here.

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