If you pay close attention in very low level light situations, you'll notice that what you do see (or at least what I see) is actually reminiscent of the RGB graininess of low level light photographs. That graininess is to my understanding caused by the variation of the number of photons hitting that portion of the receptors, which is unnoticeable when flooded with quadjillions of them in decent lighting.
So this is a nice semi-expected result in this experiment, though it does seem to be near the limit of default human perception.
I wonder how well somebody could train themselves to notice single-photon events, much like musicians can notice tiny audio events and variations.
Actually, I would guess that the 'noise' you see is from the highly noisy system of retinal ganglia and such... the eye is a wonderful thing but it has a few, shall we say, quirks. Check out this diagram:
Note that the light comes from the TOP and passes through all those layers before hitting the photosensitive one!
So - at the Earth's surface, even on a very dark night, I think you would be receiving far, far too many photons for them to each register as a sort of noise blob. More likely it is the natural noise of your nervous system as it does all the things that cells need to do and produces the slight visible side effect that's more pronounced in darkness and low contrast.
Edit: Also, since I remember this coming up in my neuro classes, this has been shown in less rigorous experimentation before:
My understanding is that the "grain" is not necessarily caused by your eyes detecting isolated photons, but rather by the electrons in the light-absorbing molecules of your rods & cones becoming spontaneously excited by ambient heat energy rather than absorption of a photon. Either way, it shows that we can indeed consciously perceive single-molecule excitation events, whatever the cause.
> but rather by the electrons in the light-absorbing molecules of your rods & cones becoming spontaneously excited by ambient heat energy rather than absorption of a photon
Agree, it's not a digital system so there is always some noise, just like you can never get perfect silence in terms of sensory perception. Your brain has also a way to project some kind of images in your mind even when you don't see anything in complete darkness, so it's far from just being the detection of photons.
> just like you can never get perfect silence in terms of sensory perception.
That's a little different because your body produces lots of noises which are only perceivable in the absence of other background noises, eg when inside an anechoic chamber[1].
It's also worth noting that senses may actually take advantage of the inherent noise to improve sensitivity of low level signals using stochastic resonance -- random resonances of noise and actual signal boosts the measured signal to a level that is detectable, thus permitting detection of signals that are actually below the (noise free) detection sensitivity. Such mechanisms have been observed in animal sensory systems, and is believed to have a role in mammalian visual processing.
There's actually a sort of native refresh rate in the eye but it isn't exact and afaik no one has really figured out how it's coded. I think I read that there is a regular drip from one layer of the retina that provides a sort of baseline rate that deviates upwards when that pathway is excited. Don't quote me on that though...
You might be interested in Elizabeth Kiersted's work with Denis Pelli (NYU) about a circumstance where people can see their own "internal" noise, based on Ramachandran and Gregory (1991)'s phantasm illusion:
Sorry for being lazy and not doing proper research, but maybe someone knows this right away. Is Sobol sequence hyperuniform? If not, is there an algorithm you can use to generate hyperuniform random variables? (Basically I am thinking that it could make Monte Carlo simulation in some circumstances a bit more effective)
If you take the 2d Fourier transform of the sequence and the low frequency components go to zero the point process is hyper uniform [1] . Poison disk noise has this property but is generally slow to generate.
What's sticking out to me is that they definitely showed individuals can detect a single photon in some sense, but they did so statistically-- No individual was ever confident that any single event happened.
There's something really philosophically fascinating going on here that I can't quite articulate. It's like, did some people really see single photons? Or did the group collectively see a photon packet?
Why don't you conduct another experiment with paramaters to answer that question, thus observing and collapsing the possibility space of distributed photon wave collapse observations into a single reality state?
It should be possible to set up an experiment with entangled photons and use your eyes as the detector. We could literally see quantum mechanical behavior with our own eyes! Pardon my crudeness but how fucking cool is that!
If you see anything it would mean that the photon had been entangled with your retina, your visual nerve and your brain. All those being macroscopic objects, you could not see any quantum behavior.
I'm not sure what would you expect to see anyway. A photon in two places at once? That's not how it works. The wave function tells you where a particle can be detected, and that can be in several places, but in the end it is only actually detected in only one of those places.
Just to note, they do hint at that in the end of the article, so you bet your socks scientists are thinking about it. It certainly was one of the first thing that entered my mind.
>We could literally see quantum mechanical behavior with our own eyes!
That occurred to me as well as I read that article. It certainly raises some interesting questions about potential observations and wavefunction collapse.
A lot of the tests of single-photon entanglement require coincidence measurements: being able to detect if two photons arrived at the same time. I'm not sure how fast the human brain would be for these kinds of measurements. People usually use FPGA-based amplifiers with fast photodiodes.
Yeah I was thinking cool, you could use cinema 3d specs for the polarizers and just need a source of entangled photons. The latter seems tricky though - all the sources I could find are infrared or lower frequency and so wouldn't be visible. Some info here http://physics.stackexchange.com/questions/172159/what-laser...
A quarter century ago we used a well characterized laser at a known power level that given a very precise wavelength and total power results in a very precise number of photons per second, like on the order of somethingE15 photons per second.
From what I remember of filters neutral density transmission is log, so its pretty easy with a laser power meter to prove a ND2.0 outputs 1e-2 of input photons and turns the remainder of photons into heat or reflects them. Show an easily measurable somethingE15/sec photons out of a laser and the meter will read 1% power. Now you can buy neutral density filters of all kinds of measurable density. And filters stack, 1% of 1% is what you'd expect, not something crazy like average or RMS or whatever. So my numbers above might be all messed up but conceptually it boiled down to create a "normal scale human brightness" fountain of a knowable number of photons per second and filter it such that theoretically about one sneaks thru every second or once in awhile or whatever.
Unfortunately we didn't have time to fool around with looking at it. From memory, I think we used it as some kind of quantum proof lab. So part one is diffraction patterns prove photons totally are definitely waves, and part two of the lab was this really sensitive photometer (essentially a geiger counter for photons) shows that each light photon is a distinct and countable bullet. And look, varying the density of the filter stack has no effect on the energy of each photon bullet it merely affects the rate at which they arrive isn't quantum mechanics spooky and wonderful? If that wasn't what we did with it, it probably should have been, or at least from memory I think that's pretty close to what we did.
I suppose in the modern era lasers are a lot more powerful so you would need a better filter and rather than the weird vacuum tube photon sensor you'd just use a COTS solar panel and measure the single electrons produced by the single photons (within solar panel efficiency correction factor etc)
You know whats really fun to do with quantum mechanics, is do a dual slit diffraction graph with a source that's like 1 photon per second so you know the apparatus only has one photon in flight at any given time. Rather than doing the two parts of my undergrad lab separately, do them together. In my infinite spare time that would be fun to build at home. I would imagine it would take a long time to gather the data, perfect for home amateur scientist types. I know what that graph looks like, and it freaks people out every time.
I only understood a tiny bit of what you said, but I do get freaked out by the double slit experiment with single photons. It's like the photon is interfering with versions of itself in alternate universes.
Can this be used for neutrino detection? Instead of ice + light sensor, you use sweatshop + human. Someone should do the math, perhaps in the right country it is cheaper to use mass indentured labor than electronics. (This is just a thought experiment, I am not supporting sweatshops)
This concept is explored in Neal Stephenson's Anathem. To avoid spoilers, I will be vague. One of the orders in the novel runs such an experiment. They have many people watching a pool or water or ice, and they independently record flashes they may see. If everyone sees the same thing, then they have captured a neutrino.
I seem to remember doing a similar problem in an order of magnitude astrophysics class I took. We calculated that there were good odds that at least one person on the planet detected a neutrino from Tycho's supernova when it interacted with the vitreous body of the eyeball. (This is from memory, so don't quote me on it --- I may have remembered the sign wrong!)
They used a microscope to look at the flashes of fluorescent light created after the alpha particle scatters from the foil.
(We could repeat this experiment in upper-level physics lab class. The teacher said it takes about 20 minutes for the eye to become sensitive enough to see flashes. He said then that the eye could see a single photon. Looking around now, I confirmed that papers of the time only said that was needed no more than 10 quanta.)
So while there may be some false positives, it's not high enough to make it useless.
While that's obviously hilariously unethical, we are beginning to use biology in combination with machines to real effect. I wonder if we couldn't breed useful biological detectors and skip having to engineer them.
In a related vein, the kid who built a fusion reactor in his bedroom--which was on the HN front page the other day--had a fascinating comment about visualizing a single neutron:
Q: How does one detect fast neutrons? A: Neutron bubble dosimeter. It is basically a tube full of gel suspending small drops of a special liquid. If a fast neutron strikes one of these droplets, the drop vaporizes and turns into a visible bubble. It still amazes me that a single neutron has enough energy to make its presence known to my naked eye.[1]
The statement about detecting a single photon by an eye is new (and possibly contradictory), but detection of a very few number of photons by human eye is not a new thing. Cherenkov radiation[1] was discovered by observing a very small number of photons (actually only a few of them) in short time interval by eyes.
The experiments were conducted this way because there were no sensitive enough photodetectors in 1930s, so the eyes were the most sensitive available tool for this kind of experiments. Eyes of a physicist were prepared to the experiments by being in complete darkness for a few hours before the measurements. Description of the experimental procedure can be found here[2].
"1972 Sakitt conducted an experiment that combined elements of signal detection and threshold theory. Two key elements of the study were a high tolerance for false positives and a multiple-choice option on deciding whether or not a light was seen. In the classic studies described above, the tolerance for false positives was so low that threshold was biased upward. Based on statistical analysis of a large number of trials, 6 photons each absorbed by one rod near-simultaneously looked "very bright," 5 photons looked "bright," 4 photons "a moderate light," 3 photons "a dim light." Two observers were able to see 2 photons as "slightly doubtful if a light was seen." One observer saw a single photon as "very doubtful if a light was seen." Zero photons were seen as "did not see anything."
That means sitting in the absolute dark for hours (you will not want to do a few short experiments, as that means dark adapting more times). It's not like you can easily repeat this with Rens of people.
> Considering only the answers with the high-confidence R3 rating, we found that the probability of providing the correct response was significantly elevated compared with all responses (0.60±0.03, P=0.0010),
For "high-confidence", that's a massive false-positive rate.
You misunderstand and subsequently misrepresent the whole experiment and paper.
Nobody but headliners (people only reading the headline) and overexcitable readers even tries to make this about "we can reliably detect single photon events". Yes that's what the headline seems to say.
The detection is clearly much better than chance. This is about exploring the absolute lower limit of human perception. It is not about "we can 'see' single photons", even though that's not even wrong - we sort-of can, the experiment shows we have a chance higher than random. On that low level it isn't about absolutes but about statistics.
I'm really disappointed in the comments here, the first time I saw this - was it on HN too not that many days ago? - comments were a lot better. Do't use a tabloid-paper interpretation and do read the actual paper too, as always headlines are useless.
"Some physicists have suggested that such experiments could test whether a superposition of two states could survive in a person's sensory system, and perhaps be perceived in the brain."
This sentence surprises me. I would have thought that maintaining coherence during the interaction with someone's eyes would be impossible. Does anyone know anything in more detail about this part?
If the eye can detect a single photon, it must mean that the triggering system in the human eye, which starts the electrical signal that carries the visual information to the brain, needs less energy than a photon contains to be triggered. That's pretty amazing to me.
How many photons does a CCD chip need to change one pixel from pitch black? A billion? 1e20? I'm curious to know.
If we could figure out how this triggering system works, we could build amazing stuff. Probably more than really good camera chips.
Electron multiplying CCD cameras can respond to single photons with > 90% quantum efficiency [1] -- that's better than rhodopsin. (I use one on a semi-daily basis.) To take advantage of that sensitivity you need to cool the sensor to -80°C so that thermal noise doesn't swamp your signal, but obviously you can't do that with your eyes.
"Activation of a single unit of rhodopsin, the photosensitive pigment in rods, can lead to a large reaction in the cell because the signal is amplified. Once activated, rhodopsin can activate hundreds of transducin molecules, each of which in turn activates a phosphodiesterase molecule, which can break down over a thousand cGMP molecules per second (Kandel et al. 2000). Thus, rods can have a large response to a small amount of light."
I am in skywatcher group, we travel to Atacama desert...
One of the experiments we did was determining maximal visual magnitude. My friend was able to see 8.1 magnitude star with 90% probability. We counted stars in triangles, 2nd person prepared maps and validated results.
This reminds me of F. Alton Everest's notes in "The Master Handbook of Acoustics" that the threshold of hearing lies coincident with the SPL of Brownian motion of air particles on the ear drum... except this is with respect to light.
Did you read the whole article you cite? The devil is in the word "ideal". If you actually read that wikipedia article: "a true single-photon source was not created in isolation until 1974." and "Another single-photon source came in 1977" and in the 1980's "thus acting as a single emitter of multiple single photons as in the experiments of Diedrich and Walther" and in the 21st century "nitrogen vacancy (NV) centers in diamond have also been utilised as a source of single photons." and "quantum dots (QDs) can emit single photons and can be constructed from the same semiconductor materials as the light-confining structures."
The definition of an _ideal_ source is "that it should be on-demand, efficient, robust and easy to implement." It seems fragile, inefficient and difficult to implement sources have been invented multiple times.
- Ambient human body temperature is a
constant source of noise as infrared
photons.
- In a dark, cold environment the human body
is radiating a constant shower of photons
in a limited spectrum. Interference patterns
could augment paths and energies of photons
in flight.
- A human might simply guess at sensations
and produce statistical anomalies that we
want to believe in.
- A guessing human might intuitively gain
an understanding of implicit tells in the
detection process, and notice cues from
the researchers, and interpret behavioral
signals to provide affirmative responses
to stimuli.
- How many photons can an individual simply
think into existence by willful thought?
Who's to say that the test subjects aren't
detecting psychic brain waves from the
researchers, by way of Vulcan mind melds
and subsequent "remote viewing" events?
> - Ambient human body temperature is a
> constant source of noise as infrared
> photons.
Which are outside of the visible range, and wouldn't interfere with the experiment, assuming they used visible range photons (the article doesn't mention this, but why would they not).
> - A human might simply guess at sensations
> and produce statistical anomalies that we
> want to believe in.
Isn't literally any study susceptible to this? Besides: "Still, participants were able to answer correctly more frequently than would be expected if they had guessed at random — and their confidence level was higher when they were right." suggests this wasn't an one-off anomaly. (Although N=3 nonetheles...)
> - A guessing human might intuitively gain
> an understanding of implicit tells in the
> detection process, and notice cues from
> the researchers, and interpret behavioral
> signals to provide affirmative responses
> to stimuli.
I think the researchers might have heard of the double-blind method.
> - How many photons can an individual simply
> think into existence by willful thought?
> Who's to say that the test subjects aren't
> detecting psychic brain waves from the
> researchers, by way of Vulcan mind melds
> and subsequent "remote viewing" events?
OP is kidding, I can identify the first statement as the pre-quantum ultraviolet catastrophe argument where everything warmer than absolute zero should emit one single honkin big gamma ray and drop back to absolute zero, whereas in practice blackbody radiation doesn't go to infinity with short wavelengths but goes to a peak (for example "red hot steel")
What I can't identify by name is the philosophical arguments in the other statements.
I'm about 90% sure one is a metaphysical Copenhagen interpretation of QM (You've heard of Heisenberg's lucky cat?) but I'm not as certain as the UV catastrophe analogy. Depends how you read it, I guess.
Thing is, we've been doing experiments for about a century where eyes were used as low photon count sensors. For example, the Geiger–Marsden experiments, a.k.a the Rutherford gold foil experiment. https://en.wikipedia.org/wiki/Geiger%E2%80%93Marsden_experim...
If what you say is true then we should have seen a signal from it long ago.
Am I the only HN reader whose bullshit detector has gone off and, admittedly without reading the study at this stage (I will attempt to do so when I get home), thinks this has all the hallmarks of future non-reproducible results?
A photon? Really?
Extraordinary claims require extraordinary evidence...and to me that's a pretty extraordinary claim. And yet when I read the report it sounds like a probability based argument from a group of 3?
ESP trials all over again anyone?
I mean, as scientists, I feel we should be cynical/skeptical...
There exist (∃) some detectors which are also human males. These three males have been statistically proven to detect single hit photons at a rate greater than chance. Yes, you are right, this doesn't suggest all humans or even most humans (discounting the blind and individuals with poor sight) can detect single photons, but they certainly have characterized these three individuals.
It's reasonable to be skeptical, but it is even more reasonable to evaluate a peer-reviewed publication in one of the most rigorous subfields of psychology (sensation & perception) after having read at least its abstract, ideally the whole paper.
Especially when papers before it have established that at most only a few photons were needed for perception. The very first line is:
"Landmark experiments by Hecht and colleagues in the 1940s established that dark-adapted human subjects are capable of reporting light signals as low as a few photons (~5–7)."
I'm probably about as cynical--at least about other people's data--as they come, but this seems pretty plausible to me.
It's been known for a while that humans can detect <SMALLNUM> of photons. I think people have looked at the fine structure of a rod and determined that it should have very high quantum efficiency. Finally, direct measurements of the electrical activity of individual (isolated) rod cells suggests that they do respond to single photons.
However, the intact retina has some "normalization" circuitry, which might wash out the signal from a single rod. Even if it makes it out of the eye, the signal has to pass through a lot of cortical processing before the subject consciously perceives it, so these results are a little surprising. However, there is some data suggesting that rats can detect the activity of a single cell in somatosensory cortex (Houwelling and Brect, 2007)[1], so it seems possible.
In summary, it doesn't seem totally outlandish based on what we already knew but...replications are good.
I'm honestly a bit surprised that such an article is placed in Nature, as there seem to be a couple questionable details in the article regarding the experiment:
- Only 3 volunteers on which the experiment has been tested
- The volunteers were left "in total darkness for around 40 minutes" before the actual experiment
- "In many cases, they got it wrong; this is to be expected, given that more than 90% of photons that enter the front of the eye never even reach a rod cell, because they are absorbed or reflected by other parts of the eye. Still, participants were able to answer correctly more frequently than would be expected if they had guessed at random and their confidence level was higher when they were right."
- The three volunteers sat through a total of more than 2,400 trials in which a single photon was emitted (and many more in which it was not).
- That high volume of testing, the researchers say, gives them strong statistical evidence of single-photon detection
- The participants had to say on which occasion they thought they saw a photon, and how confident they were (on a scale of 1 to 3) about their sighting.
In summation, they put 3 volunteers for 40 minutes in total darkness, then performed more than 2400 trials in total (i assume 1000+ trials per person, taking into account the tests in which no photon was emmitted). "Many" times the volunteers guessed wrong, but when they guessed right they were pretty confident of it (using a rather simplistic scale of 1-3).
What I'm seeing with this experiment is a result which is more confirmed due to psychological bias rather than actual results by putting these volunteers in a straining test. How would you, as a volunteer react, if you were left in the darkness for such a long test duration and would asked over a 1000 times whether you have seen a flash.
Edit: After having read the actual paper on the methodology, I do retract my comment.
In the typical psychophysical study on perceptual thresholds, participants are given a two-alternative forced-choice test: a stimulus (here, a photon) is placed in one of two intervals at random, and the participant guesses which interval had the photon. Using this design, a bias that systematically selects one response more often than the other will lead to performance below chance. Finding that performance is significantly better than chance is evidence that the observer can detect a single photon. Demonstrating that performance is reliably above chance requires many trials because the level of performance is close to chance. Compare this to a yes/no design, where a bias can create the appearance of an ability to detect a single photon where there is none.
The reason for waiting 40 minutes is that the eye and brain adapt to darkness. If this experiment were performed outside in daylight, it would be impossible to detect a difference of 1 photon. Only when the observer sits in a room without light can the brain adapt and have its greatest sensitivity to light.
Finally, note that the logic of this study is an existence proof that people can detect single photons. Selecting three normal observers and finding that all of them have this capability is reasonable evidence that most normal observers can do the same, unless you have some specific reason to believe that these observers are unrepresentative of the population (as the researcher in the press release did re gender differences).
I have a slight correction to my earlier comment, in which I said "Using this design, a bias that systematically selects one response more often than the other will lead to performance below chance." A bias of this kind will drive performance closer to chance. Performance that is significantly below chance would be evidence that observers can see single photons, but that they have the response labels reversed in their minds.
Averaging across subjects’ responses and ratings from a total of 30,767 trials, 2,420 single-photon events passed post-selection and we found the averaged probability of correct response to be 0.516±0.010 (P=0.0545; Fig. 2a).
Edit: Having (quickly) read the paper, it does seem the psychology of the volunteers was taken into proper consideration, I stand corrected:
Before collecting data, subjects were extensively trained using a classical light source with photon number between 1 and 15 photons at the cornea (Supplementary Fig. 4a). The improved performance with experience is clearly and quantitatively visible (Supplementary Fig. 4b,c). Subjects typically required 6–8 sessions, performing one session a day, to reach their optimal performance level (Supplementary Fig. 4b,c). Each session took~2 h, when including dark adaption.
During data acquisition, each subject went through up to 20 sessions. Still this high amount of sessions was not enough to obtain statistically significant performance for individual subjects, and therefore we pooled the data together to increase significance (Fig. 2a–d). As subject’s sensitivity and criteria used to assign the confidence ratings might vary in psychophysics trials28, we aimed to minimize or normalize possible factors causing variability to achieve maximum sensitivity and similarity across subjects by using extensive training of the subjects and using our 2AFC paradigm.
Additionally, the research does have interesting observations:
Surprisingly, a strong dependence on the temporal separation of the two events was observed peaking at ~3.5 s, with a decay time on the order of seconds (Fig. 2c). Such a long timescale phenomenon represents more than an order of magnitude disparity with the known integration time of the visual system4. This result directly shows that the probability of correctly reporting a single photon is highly enhanced by the presence of an earlier photon within ~5 s time interval.
Thus, consistent with both observations, we suggest that the detection of a single photon – or equally a photon-like noise event (that is, spontaneous isomerization) – temporarily increases the effective gain of the visual system under extreme low-light conditions, such that a second temporally coinciding photon (or photon-like noise event) can be behaviourally detected with a higher probability.
What do you mean it is "confirmed due to psychological bias"? If they answered better than chance, and it was statistically significant then what's the problem?
I haven't read the full paper, so this is only speculation.
I expect they would have counted the number of times the volunteers claimed to have seen a photon, both when a photon was emitted, and when they only said that one was emitted.
If the detection rate is significantly higher for "real" emissions than for the "fake" emissions, then you can draw a statistically significant conclusion (aside from the fact that there were only 3 test subjects).
Just a note, when the number of volunteers is less than the number of authors, you're probably looking at self-experimentation.
It's not uncommon when you have a cool idea you want to test that doesn't rely on naive subjects and it would take longer to get permission to & recruit outside volunteers -- just grab a few people from around the lab and try it out.
Kwiat was already recruiting undergrads in 2013 for this experiment. If I recall, he did not yet have a reliable single photon source but was expecting to have it very soon.
I was in his undergrad quantum physics (for engineers) course at the time.
If they had not detected even once, then your points hold. But they did detect, so the point is that they were able to see? What more do you want? It simply shows that people can sense photons. Maybe not all the time, but sometimes for sure.
Of course the real test here will be a duplication study, but with more than three test subjects. The selection bias in the study as performed is essentially unacceptably huge.
I don't count that against this study -- it isn't about determining the effects of a drug or something like that. If we can show that there exists one person that can detect a single photon in a statistically significant way (vs random guessing), that still seems like a fascinating result.
Look, I'm in laser plasma physics, and people conflate photons and monochromatic plane waves in my field all the fucking time. Even worse, they conflate plasma waves with phonons * shudder * . There is similar mathematics that describe both but conceptually they are different things.
I want to heat some micro particles in an heterogeneous mixture. However, they need to be heated with precision so that the other components of the mixture don't get melted. So, I was thinking in getting a laser to do that. The laser would need to have a wavelength that targets only the component that I want to heat.
So, I am more on the plasma side than the laser side, unfortunately, so get a second opinion :) but I'm not sure it would. First of all, when talking about heating, you're mainly relying on dielectric heating[0], which depends on the dipole moment (perhaps) and polarizability of the things you're looking at. The wavelength might play a role but the idea is dielectric heating is a classical phenomenon, not quantum. I'm don't want to misunderstand your idea, but it sounds like you are applying intuition from QM regarding a material's absorption spectrum, which is,obv., quantum and thus selecting regarding wavelength. Dielectric heating will affect both species regardless given if both can be polarized leading to heating.
Now, say one is more polarizable than the other and so is heated first. However, a more important consideration here is that this is a heterogeneous mixture, so I think what is more likely is heat will be even distributed between the species. You're essentially trying to achieve a non-equilibrium state (high temp in one species and not the other) when one species is on top of the other! On shorter time scales, the more polarizable/polarized stuff might be "heated" first but that heat will eventually move to the other species from collisions leading to equal heating.
So it all depends. Will your target species be heated to melting before that heat transfers to other stuff? This does depend on the coupling of the laser energy to the particles but it also depends on the time scale it takes to melt too and the collision frequency between target species and other species. So, as you see, it depends specifically on the materials you're thinking of, which you could probably look up.
Honestly, you could try something much simpler, like just choosing species based on their melting point. Obviously, your question seemed to imply that they melt at similar melting points and you make to make species A melt before species B. If you just choose species with diff species with diff melting points, you don't even need a laser, just a heat bath.
- Will your target species be heated to melting before that heat transfers to other stuff? = That's the plan, the heat will propagate so I want to apply just enough heat to minimize the amount of heat transferred. They have different melting points: around 50C in difference.
But we don't "see" imdividual photons. The cell reacts to a chemical reaction/ absorbtion in the photopigment, thus dependent of the energy of the photon, which is directly related to the frequency of the wave duality of that photon.
> The cell reacts to a chemical reaction/ absorbtion in the photopigment, thus dependent of the energy of the photon, which is directly related to the frequency of the wave duality of that photon.
This is what we call "seeing" :)
This is like saying the atoms in your fingertip never "touch" the elevator button's atoms. Instead, a strong oppositional force develops when the atoms in your skin get close to the atoms in the button. While true, that's exactly what we call "touching"
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So this is a nice semi-expected result in this experiment, though it does seem to be near the limit of default human perception.
I wonder how well somebody could train themselves to notice single-photon events, much like musicians can notice tiny audio events and variations.