Note that the FSF has no problem giving an RYF certification to hardware with unupdatable binary blobs, as long as those blobs reside in a separate chip like an SPI flash. It's not a measure of security or maintainability. Of course whether the FCC label will be one either remains to be seen.
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It is not more unsafe than fixed-sized arrays on the stack and stack clash protection (which you need anyway) protects against this. Also if you compare with C++ and use std::vector, surprise, a CVE about to happen: https://godbolt.org/z/cTG71aTsf
(yes, one can activate library assertions, but still - by default - unsafe)
The various code snippets in the article don't compute the same "function".
The order between the min() and max() matters even when done "by hand".
This is apparent when min is greater than max as the results differ in the choice of the boundaries.
Funny that for such simple functions the discussion can become quickly so difficult/interesting.
Some toying around with the various implementations in C [1]:
> To optimize this ratio in practice, we used the multi-pixel sensor of an electron multiplying charge-coupled device (EMCCD) camera as our idler detector (Fig. 1a). As the EMCCD can detect multiple photons simultaneously, it allowed us to identify and reject, that is, post-select, all events other than those where a single-photon pair was generated with a higher efficiency than with more traditional single-photon avalanche diodes (SPAD)
How is it possible to both detect a photon and then allow it to travel to the human eye? Wouldn't detection require absorption of the photon?
There is a process called spontaneous parametric downconversion (SPDC), where if you shine laser of frequency f at a crystal, it will with small probability p emit two photons of frequency f/2 (energy conservation in play here).
If done correctly, the outgoing laser light and the two photons all travel in different directions and so can be separated and further directed using mirrors or optical fiber cables.
Because the process is non-deterministic, what we usually do is direct one of the photon beams towards a "heralding" [1] detector, while the other is directed towards the optical setup where we need a single photon [2]. If at a given moment a photon pair is produced, then the heralding detector will click; which tells us that is also a photon currently in our optical setup.
Finally, there is a ~p^2 probability that two photon-pairs will be produced at the same time by this process (and p^3 etc). To eliminate this possibility, in this experiment their heralding detector can detect how many photons landed on it any given moment. So if they see 2 or more photons in their heralding detector, then they discard this run, because now there are multiple photons heading towards the human eye.
[1] Herald as in the guy who announced that the King was approaching.
"SPDC is a quantum optical technique in which correlated pairs of photons (called signal and idler) are produced probabilistically from a higher energetic pump photon in a non-linear crystal following energy and momentum conservation16,17 (Fig. 1a). By detecting one of the photons (idler) and sending the other (signal) to the observer’s eye..."
I suppose conservation of momentum allows them to guarantee pairs, in which case a photon in one direction guarantees a photon in the opposite direction.
> How is it possible to both detect a photon and then allow it to travel to the human eye?
Leonard Susskind explained it like this in one of his lectures (they are on YouTube, he's an excellent explainer):
From the moment the photon is emitted, to the moment it's detected, the photon exists in entanglement with all the intermediary things it "touched". Only at the final location it's "absorbed" (with a probability). At the intermediary locations the probability ended on the low side so it passed through.
Interesting study, though if you look at the results 'significantly above chance' looks to be 0.60 +/- .05, which is indeed better than 0.50 but not what anyone could call reliable detection.
I wonder if trained owls could detect single photons, or if their night vision is based on just having much larger lenses that collect more light?
It seems that all rods in retinas are activated by single-photon-absorption, it's just about how many have to be activated to generate a neural signal.
Owl eyes have really cool adaptations (see https://abcbirds.org/blog/owl-eyes/). If we can somewhat detect single photons, it seems very likely owls could do it much more repeatably.
It wasn’t clear to me whether that 0.60 accounted for the fact (mentioned in the overview) that only 10% of photons reaching the eye actually make it through.
It definitely is. The retina "measures" photon positions, which is why you see images. Observation is just interaction, no need to consider whether A can observe B. If they interact, some kind of observation takes place.
When you look at the flickering pattern a laser pointer makes on a rough surface, that flickering pattern is similar in nature to the double slit interference, and you are seeing it with your eyes.
Don't forget that the interference pattern is a statistical one, you need to average over a number of photons to "see" it emerge.
Yep! Any interaction counts. If something interacts with a photon, and that interaction can only happen if it goes through one of the two slits (i.e., it tells you "which way" the photon went), then the interference pattern will disappear.
What escapes my understanding with the whole "interaction is observation" thing is that I don't get how anything could ever not be interacting with a whole lot of other stuff. Gravity and EM fields are everywhere. Even if photons are somehow immune to that (which, they're not, because gravity can re-direct photons) it's my understanding that we can see the same interference patterns with particle streams of ordinary matter, and I can't for the life of me figure out how those could ever not be interacting with basically everything remotely nearby, including the entire test apparatus.
And now you understand why "quantum gravity" is such a big question in physics right now! We don't understand it all. I actually don't know anything about how EM fields affect superposition, perhaps someone else can chime in.
Yup, everything interacts with everything close by all the time.
The important thing is by how much, and what sort of interference patterns can this produce.
As it turns out, interference is quite hard to produce randomly because two fields only produce wavering patterns when their frequency and other parameters are almost equal.
So yes, the ball you just threw to your friend is actually spread out over a whole region, that spread is about 10^-34 m so it impact is not visible at all.
The short answer (as I understand it) is that decoherence is not binary. The gravitational field may be able to partially resolve the position, for example, and so you only get slight reduction in interference.
Yes it could.
But, it requires absorbing radiation further down in the infrared and power is an issue to consider!
What radiates more your ears or a sun?
Work and studies of metal films and thin films as well as their fabrication has been going on for more than a century.
Basically since electromagnetism is popular.
Fabrication tools for thin films have improved a lot over the past decades though. We can now fabricate exotic structured matter at the nanoscale that doesn't respond as the bulk counterpart.
While I would agree with you that media often phrase thing the mentioned way, I would prefer here to state that X implies Y.
The question is more whether it will be picked up more widely at industry scale.
We took great care to show real-world applicability of our work.
I am a co-author of the mentioned work and very surprised (but pleased) to see it here.
I think that this is a good overview!
On the material part the sweet spot is the transition from assemblies of particles to forming a continuous path (film).
For the application you indeed need sunlight.
The sun is a strong radiation source!
Putting your face under a light bulb might cause other issues.
Glasses is here the most accessible example to illustrate the work from the research to the application. I think we can get creative about other use cases.
Could it be useful for automobile windscreens? The article says it's solved for cars with embedded wires but this is not generally seen in the front windscreen - probably because it impairs vision and maybe even makes the glass less robust. I checked and it seems now we do have windscreens with electric heat but perhaps your system could be adapted to the lower end cars.
The only car I’ve ever owned with a heated windscreen was a Ford Focus. It worked a treat and was still really useful even after some of the conductors corroded and stopped working.
Oh man, our Ford Mondeo (UK must be 15 years ago) had the fine heating wires in the front windscreen - best defrost/demist ever, almost instantaneous compared to every other vehicle I've driven. Definitely a feature that would sway me from choosing one vehicle over another!
Not really. Windscreen heating is quite common in the industry, and the patents lie with the glass suppliers (No Vehicle Company builds their glass themselves). Most common techniques are thin tungsten wires or a heatable thin metal layer which additionally acts as IR-reflection.
You say it’s common but it didn’t used to be. It was common on Fords but no other vehicle manufacturer had it. Rear window heating, sure. But not front windscreen.
Moreover, Ford dealerships (in the U.K. at least) would boast that they owned the patent.
Looking online, I can see lots of references on car enthusiast sites talking about Ford owning the patent but any documents on the patent I find states it’s owned by an independent window manufacturer (like you suggested it would be).
So that leaves me wondering if either Ford had the patent but then sold it (unlikely in my opinion), or if they simply bought exclusively rights?
Thanks! Apologies if I sounded overly salty/negative, that was not my intention. I don't ski, but obviously skiers also deserve seeing where they are going, it has safety benefits. :)
I'd have to say that any small heat source might make this technology quite workable. Even conducting a bit of heat from your head to the glasses frame, to the lens coatings, perhaps?
https://ryf.fsf.org/
Again, decades ahead.
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