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Photons

All articles tagged with #photons

Quantum Switch Rewrites Heat Flow by Scrambling Cause and Effect
science1 month ago

Quantum Switch Rewrites Heat Flow by Scrambling Cause and Effect

Researchers used a quantum switch to create indefinite causal order between two heat reservoirs, effectively allowing heat to move from cooler to warmer regions and challenging a straightforward interpretation of the second law; an optical experiment with split photon beams matched theoretical predictions with over 99% fidelity, highlighting a potential bridge between quantum and classical causality and possible future photonics applications.

via Yahoo|
#heat-flow#indefinite-causal-order#photons
Two clocks in the Sun: neutrinos escape in seconds while photons diffuse for 170,000 years
science1 month ago

Two clocks in the Sun: neutrinos escape in seconds while photons diffuse for 170,000 years

Fusion in the Sun produces neutrinos and photons that travel on very different timescales: neutrinos, interacting only weakly with matter, exit the core in about 2 seconds and reach Earth with only the minutes-long light travel delay, while photons undergo a long, random-walk diffusion through the dense radiative zone—being absorbed and re-emitted countless times—taking roughly 170,000 years before the energy reaches the photosphere. The photons reaching us are not the same particles from the core; energy is redistributed and carried outward, with convection taking over in the outer layers. This dual-timeline view underpins solar physics and helped resolve the solar neutrino problem via neutrino oscillations.

via Space Daily|
#fusion#neutrinos#photons
Sunlight-Powered Quantum Entanglement Demonstrated for the First Time
science1 month ago

Sunlight-Powered Quantum Entanglement Demonstrated for the First Time

A team used a Fresnel-lens concentrator to focus sunlight onto a crystal, generating polarization-based entangled photons without a laser. The photons achieved ~94% similarity to a perfectly entangled state and violated Bell’s inequality, marking a proof-of-principle step toward cheaper, energy-efficient quantum tech for satellites and remote stations—though a practical, deployable sun-powered entangler remains to be built and improved.

via ScienceAlert|
#optics#photons#polarization
Why Sunlight Takes 170,000 Years to Reach Earth
space2 months ago

Why Sunlight Takes 170,000 Years to Reach Earth

Sunlight that reaches Earth today began its journey deep inside the Sun. In the dense core and radiative zone, photons propagate by a random walk, with a mean free path of about 0.09 cm and billions of absorptions/re-emissions that prevent a straight path. This diffusion takes roughly 170,000 years on average, and only when photons reach the photosphere do they escape into space, taking about eight minutes and twenty seconds to reach Earth. Separately, astronomers measured extragalactic background light and estimate that about 10 billion ancient photons from distant galaxies strike your skin each second outdoors, underscoring that much light comes from far beyond the Sun.

via Futura, le média qui explore le monde|
#diffusion#extragalactic-background-light#photons
Quantum test confirms negative time is a real, measurable effect
science2 months ago

Quantum test confirms negative time is a real, measurable effect

Photons passing through a rubidium atomic cloud can appear to spend a negative amount of time inside the cloud when inferred from their arrival times. By performing ultra-weak measurements of the atoms, researchers found the dwell time measured in the atoms matches this negative value, showing negative time is a real, measurable quantum effect that fits standard physics and is not just an artifact.

via ScienceDaily|
#atomic-physics#photons#quantum
Photon Truncation Won’t Create Infinite Light, Scientists Say
science2 months ago

Photon Truncation Won’t Create Infinite Light, Scientists Say

UiO physicists explore what happens when you “cut” a photon by removing a reflecting mirror. The resulting state is a complex quantum superposition where the photon number can, in theory, range from zero to infinitely many, but in practice the expected count is finite and depends on how quickly the mirror is removed—the faster the removal, the more photons can appear, yet infinite photons would require an impossibly instantaneous action. The work also highlights that vacuum energy can transform into real photons near the boundary, illustrating the strange, wave‑particle nature of light in quantum regimes.

via ScienceAlert|
#optics#photons#quantum
Sunlight’s Hidden Odyssey: 170,000 Years to Escape the Sun
science2 months ago

Sunlight’s Hidden Odyssey: 170,000 Years to Escape the Sun

Sunlight takes about 8 minutes to reach Earth, but the energy moves outward from the Sun’s core via a random-walk diffusion process. A 1992 study showed the journey is much longer than straight-line travel, and a density‑varying model revealed the photon step length is under 0.1 cm for most of the Sun’s interior, pushing the diffusion time from tens of thousands of years to roughly 170,000 years before the photons reach the surface and head to Earth.

via ScienceAlert|
#diffusion#photons#random-walk
Fireflies Upend a Century of Brightness Measurements.
science2 months ago

Fireflies Upend a Century of Brightness Measurements.

A new analysis recalibrates how bright a firefly’s flash really is, showing the long-accepted figure of 1013–1014 photons per flash is overestimated by 2–3 orders of magnitude. Using a simple lux meter and biochemistry checks, researchers found that old brightness estimates translated into modern units likely overstate output, suggesting other classic measurements may need revision and offering new insights into firefly vision and the biochemistry of their light production.

via Yahoo|
#fireflies#luciferase#luciferin
Quantum experiment reveals negative weak time for photons in atomic cloud
discoveries2 months ago

Quantum experiment reveals negative weak time for photons in atomic cloud

University of Toronto physicists measured a negative weak value for the time transmitted photons leave atoms excited in a rubidium cloud, using weak measurement and postselection to link a negative group delay with a measurable phase shift in a probe beam. The result clarifies how quantum interference and dwell-time concepts govern light–matter interactions, without implying backward time travel, and has spurred further work extending the weak-value framework.

via The Brighter Side of News|
#atomic-excitation#discoveries#negative-time
The sun’s slow energy highway: millennia inside the Sun before eight minutes to Earth
science2 months ago

The sun’s slow energy highway: millennia inside the Sun before eight minutes to Earth

Eight minutes after leaving the Sun’s surface, sunlight reaches Earth, but the energy inside each photon spent 10,000–170,000 years zigzagging through the Sun’s dense core via countless absorption-and-reemission events; neutrinos escape in about two seconds, revealing the core’s workings, while the outer radiative and convective zones, and the photosphere, shape the final journey of energy to us.

via Space Daily|
#energy-transport#helioseismology#neutrinos
Quantum Oddity: Photons Appear to Exit an Atomic Cloud Before Entering
science4 months ago

Quantum Oddity: Photons Appear to Exit an Atomic Cloud Before Entering

Physicists used weak measurements to probe how long photons spend in a rubidium atomic cloud as they travel straight through. They found a negative dwell time for those that pass, meaning the photons seem to arrive at the far side before they would have if they had spent time in the cloud, a result that matches the negative time inferred from arrival statistics. The effect is not an artifact of the measurement but a real, measurable quantum phenomenon explained by standard physics, highlighting that negative time in quantum interactions is possible and observable.

via SciTechDaily|
#negative-time#photons#quantum
Quantum test confirms photons can exhibit negative time
science4 months ago

Quantum test confirms photons can exhibit negative time

Physicists report that photons passing through a cloud of atoms can appear to exit before entering, i.e., negative transit time. In a Physical Review Letters study, the researchers monitored the atoms’ excited state during the photon’s passage with a second readout beam and used weak measurements, requiring about 1 million trials across seven parameter sets to obtain a clear signal. The result, which aligns with standard quantum mechanics, shows transmitted photons can have negative time while scattered photons carry positive time, keeping the beam’s average time nonnegative. The next step is to test time effects for photons that don’t pass through the cloud.

via Live Science|
#atomic-physics#negative-time#photons
Sunlight Sparks Laser-Free Quantum Ghost Imaging
science4 months ago

Sunlight Sparks Laser-Free Quantum Ghost Imaging

First demonstration of sunlight-pumped spontaneous parametric down-conversion (SPDC) paired with ghost imaging, producing quantum-correlated photons with a passive, sunlight-powered source. The setup achieved about 90.7% ghost-imaging visibility (near 95.5% with a 405 nm laser) and used a sun-tracking system and nonlinear crystal, suggesting potential for quantum imaging in remote or space environments while highlighting future gains from improved collection, crystal design, and reconstruction methods.

via SciTechDaily|
#ghost-imaging#photons#quantum