This crystal can split light particles
ฝัง
- เผยแพร่เมื่อ 13 มิ.ย. 2017
- How unusual non-linear crystals can entangle particles of light, or photons.
Thanks to non-profit edX.org for sponsoring this video. Go to bit.ly/edXPhysicsGirl to learn more about MIT's Circuits and Electronics course or other classes from some of the top universities in the world.
Quantum entanglement involves a special process of splitting photons into two. But it involves a process and a crystal that can split photons. How does that lead to entangled particles?
To find out more about the specifics of how to entangle photons, check out this awesome video from whentheappledrops • How to Produce Entangl...
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Creator: Dianna Cowern
Research: Sophia Chen
Thanks to: Jabril Ashe, Ashley Warner, Rebecca Holmes and Dan Walsh
This is really interesting, but did you explain how it works?
Did I miss something?
All I got was "one goes in, then magic happens, then two come out."
Yes, she did at 2:38 The bbo crystal absorbs the incoming photon and emits two photons. But she didn't explain the "vacuum energy fluctuations" thing, though
Yeah, that's kind of what I meant.
She talks about how it is impossible to split photons, but then she says that the bbo crystal does it anyway.
It's just a little frustrating if the most interesting thing about this experiment is brushed away with "vacuum energy fluctuations" and then lacks an explanation of what that means.
Especially if she explicitly points it out like that.
I understood that the crystal doesn't split the photon directly, it absorbs its energy and then gives it off in the form of two other photons, but how it does that really should've been explained in more depth than "vacuum energy fluctuations" :/
well, maybe most of the people that watch this channel is not searching for a boring super technical explanation, but more for some funny thing that keeps them entertrained, plus, give them a understanding of what is being studied
I'm taking this from my other comment, but... Having worked with BBO crystals for the past year, I can confidently say that it is much much harder to explain than you may think. What you can imagine is happening is that the quantum vacuum fluctuations (the sea of particles and anti-particles popping in and out of existence) is also providing photon pairs that are being created and then annihilated. What this crystal is doing is effectively taking the single incoming photon (in my case, 405 nm) and "donating" its energy to a virtual photon pair of two 810 nm photons thus destroying the original 405 nm photon and "creating" two 810 nm photons. It is a bit more complicated since the two generated photons don't TECHNICALLY have to be entangled since there can be higher order processes that result in the energy of the outcoming photons to be not quite the same, but this is the general idea. If you want a similar phenomena to look into that is effectively the same process, google the "dynamical Casimir effect".
The reason she just left it at "vacuum energy fluctuations" is because that's the default answer you get whenever you google this topic because no one really has a fantastic explanation for what is going on and you really need graduate level physics knowledge to even have a chance of understanding what is happening. Despite having worked on projects involving SPDC, I still think of it as a magic crystal that splits photons just because it's easier for me than thinking about what is actually happening.
"so how do you make entangled photons?"
*I DUUUHHNOOOOH* 😂😂👌
Hey! This is awesome! I actually completed the experimental quantum bell test mentioned in the beginning of the video (and managed to violate Bell's inequality!!!) as part of my curriculum for an advanced experimentation laboratory course I completed this past spring semester. Working with and learning the physics behind beta-barium borate crystals was a blast, and vastly increased my understanding of non-linear optical components and their application in exploring quantum effects. Thank you for producing this fantastic video, Dianna!
Sweet boy hahaha
best line of a theorist on a lab "I don't belong here"
hey Diana!!! it's been a long time since I wanted quantum mechanics related videos from you... and finally you're doing super great!!!!
your " not so good examples"(really awesome analogies infact!) are what makes your videos incredible!!!
Really? No explanation at all? Not even a diagram explaining what a non-linear crystal is?
A bit disappointed. I expected more of an explanation as to how 1 photon "becomes" 2, and why it only happens every billion photons.
Google "hyperpolarizability tensor" (really that is the underlying physics). The conversion efficiency of a nonlinear process (like turning one photon into two) depends on the intensity of the incident light. So you can make it more efficient by just cranking up the power--but get it too high, and you'll blast a hole in the crystal ($$$). Which is kind of a bummer if you're the grad student working in the lab...
@The757packerfan, Having worked with BBO crystals for the past year, I can confidently say that it is much much harder to explain than you may think. What you can imagine is happening is that the quantum vacuum fluctuations (the sea of particles and anti-particles popping in and out of existence) is also providing photon pairs that are being created and then annihilated. What this crystal is doing is effectively taking the single incoming photon (in my case, 405 nm) and "donating" its energy to a virtual photon pair of two 810 nm photons thus destroying the original 405 nm photon and "creating" two 810 nm photons. It is a bit more complicated since the two generated photons don't TECHNICALLY have to be entangled since there can be higher order processes that result in the energy of the outcoming photons to be not quite the same, but this is the general idea. If you want a similar phenomena to look into that is effectively the same process, google the "dynamical Casimir effect".
@Brad Williams, You are right and wrong. That describes how non-linear interactions work, but it does not explain how the photons split. And turning up the intensity does not technically increase the efficiency (since it is a purely random process), it just increases the amount of down-conversion that occurs.
Thanks guys!
Ryan Wilson : Thanks for the explanation. If you ever decide to post a video about your work, I hope I can find it. I love science channels like PBS Spacetime precisely because the content is sometimes way over my head. Physics Girl videos are excellent, but rarely cover the hard math stuff that I need to understand before I can finally comprehend the original research papers.
I have a question:
Is light actually a stream of particles? Is the light source emitting photons? If this would be true, we could talk about density of photons in space - but we can't. Intensity of light is defined by the amplitude of a wave and not number of photons... Are we emitting particles of air, when we make a sound?
Wave can also carry the energy. I think, that photons can be treated as "packs" of energy, carried by the wave. Atoms in a source of light create those waves by vibrations... Energy is released through those waves...
Is it possible to send 1 photon into 1 bbo, then those 2 photons into 2 bbo, and so on? And will these 4 photons will be entangled?
i think they will only be entangled as 2 pairs instead of 4, the first pair of the photons have to just conserve the intrinsic properties of their mother photon and the same goes for the second pair. But we can't know exactly for example what state the first photon of the second pair is after knowing everything about the first photon of the first pair. (I think LOL)
+NEON DOG Excellent question. There's a property called the "monogamy of entanglement" which probably answers your question in the negative. (I'm assuming you're referring, implicitly, to maximally entangled photons.)
You could in theory send the two down converted photons into two more BBO crystals, but you will not get four entangled photons (especially since only 1 out of every 10^12 photons actually experience down conversion). The SPDC photons only retain information directly from their "parent" photon, but not the entangled state it was in.
We need more hard-core physics videos from you Diahna!!!!!
I'm starting to work with bbo crystals as well and this video was actually really helpful for me to understand them better. Thank You!!!
"Photons are elementary particles, my Dear Watson"
-Dianna "Physics Girl" Cowern, 2017
binky2819 I love that the other girl appearing in the video was Rebecca Holmes
Off topic; but, did you know? That parsley is a great addition to a green smoothie, especially if you are also adding in raw garlic.
dont think id fancy garlic and parsley in a green apple smoothie
I haven't added green apple, yet. Thanks for the suggestion.
binky2819 is that really her last name haha? cow urn.. I wonder what the person who chose that last name had happen, maybe they loved their cow and it died and they wanted it's urn to be in their name
I'd love to see a video just explaining at the microscopic level how entangled photons come out from one of these crystals.
You didn't actually explain how the process happens :(
Very basically, the crystal destroys one photon and takes its energy, then uses it to create particles out of 'nothing' (the whole vacuum fluctuations thing). Because particle creation has certain rules these photons are 'twins'.
HoxTop because it's physics girl. She never explains things properly because she CAN'T. At the end of the day, she's just a pop scientist.
Le fyziks guise She's far from perfect, but she's helping get people/kids interested in science. these days, that job might be more important that a lot of the actual scientific research being done. you sound like you have a beef with her.
But you've just reinforced my point. If her job is so damn important, then she'd better make sure she's near perfect, otherwise she's doing a lot of kids, and science in general, no favours. There are much better channels on TH-cam.
You want to explain QED to kids? Good luck. It's hard enough to explain it to educated adults, and even then you're only describing what's happening as best you can. Nobody has any idea of how it works, only that it does, and that these interactions can be described as physical laws.
An question, Does these entangled photons have a half the frequency of the "mother" one?
I'm assuming so, if they can up-convert two greens to one UV.
Probably slightly less than half, since some energy would be retained in the crystal as heat. Thermodynamics still applies.
The energy of a photon is E = h * f.
With h being a constant (Planck constant), you basically get E ~ f.
Energy has to be conserved (in the whole system of crystal and photon/s) so you now have two photons each with half the energy, meaning each photon also has half the frequency.
Yes, they have twice the wavelength and half the frequency.
@willythemailboy2, They have exactly half the frequency. Despite the crystal being necessary for the conversion, the state of the crystal is unchanged and no energy is lost through this process.
Ryan Wilson Actually the crystal can get a small kick from momentum transfer. IIRC this results an a but of wavelength spreading at room temperature.
This was great. Gonna check out edX for sure too!
I was just getting back into circuitry so it would be nice to dive deeper
A very fascinating light particle experiment. "Chinese brand BBO crystals " from CRYSMIT are used in nonlinear optics to split photons into pairs of lower-energy photons, a process known as parametric down-conversion. This property is valuable for quantum experiments and the generation of entangled photon pairs.
What happens if you feed the output of the nonlinear crystal into a second nonlinear crystal?
someone in a parallel universe gets hit with a photon and cant figure out where it came from y
If it has the right structure it may (One in trillions chance) split the second photon into an entangled pair, but this ruins the original entanglement, so you still have only two entangled photons.
do photons really exist?
or light is it just a propagation wave in the medium?
how come photons "speed up" after passing through glass?
from where they gain their energy back?
maybe Its not the speed of light but the rate of induction.
just like sound.
I would love to hear your opinion on this theory
thanks
Yes, photons exist. Historically the photoelectric effect was the first conclusive evidence. But it left people wondering if these photons where 'really particles'. Could you for instance play billiards with them? The answer came with the discovery of Compton scattering. Yes, you can shoot photons at electrons and have them give an electron a kick, and the photon comes out with in a different direction, with different energy, just like a billiard ball (well, a relativistic billiard ball with zero restmass, so not your everyday play toy, but still all the laws of particle collisions apply to photons).
Photons do not slow down or speed up. They move at the speed of light always.
An beam of light normally consists of huge numbers of photons. Its behavior is described very well by a classical wave. If the beam enters glass, the photons are scattered by the outer electrons of the atoms in the glass. Because there are so many of them, we can treat this problem in terms of wave theory. From that point of view the electric field of the incident wave makes electrons wiggle. These oscillating electrons emit secondary electromagnetic radiation. This happens all throughout the glass, so we have the incident wave and a huge number of scattered waves that we need to add up to obtain the total field. Actually doing such a summation is incredibly difficult in general, but fortunately there are circumstances that allow mathematical tricks to do the sum. The most important of these is to treat the medium as randomly distributed (independent) scatterers. This applies to glass to a fair extent. Then the so-called Ewald-Oseen theorem allows us to add up all the scattered waves, and the result is absolutely amazing:
All the scattered fields add up two TWO waves: one wave that is an exact copy of the incident wave except with a minus sign, and a second wave that is an exact copy of the incident wave, but with a slower speed of propagation. If we now compute the total field, that is the incident field plus all the scattered fields, the incident field drops out entirely, and we are only left with the slower wave. This is why people say that light slows down in glass, and we describe it by the concept of refractive index.
But all of this wave theory should not mislead you into thinking that the myriad of photons in the beam all slow down. They are scattered by electrons in the glass, and if you insist on picturing them as billiard balls (which is not a very wise thing to do in this context) you find that they takes lots of detours due to the scattering, and this is what slows down their collective propagation. It is the difference between a group of soldiers marching straight ahead, and a crowd of meandering shoppers in a mall. The latter's walking speed may be the same as the soldiers, but collectively the shoppers make less rapid progress because they wander from item to item instead of straight ahead.
can you please have a beef with that guy:
/watch?v=HbijQzkJFAo&t=1060s
OH and you too Physics Girl! youtube drama Is where the Isht is!
No, there is no point. I'm just explaining some very basic physics discovered a century ago. The person in the video you link to claims that most 20th century physics is completely wrong, offering as main 'argument' his own authority based on alleged superior private insight. Such an argument is irrefutable, in principle.
@materiasacra, I just want to point out something that you may not be aware of. While the photoelectric effect is typically used as evidence for quantized packets of light (photons), this is not necessarily true since the photoelectric effect can also be explained using semi-classical theory (a classical wave with a quantized atom). It's actually a very interesting explanation if you care to look at it.
omg i was a test subject for the single photon expirement! So glad to see it featured here!
Thank you for one more very interesting video.
And I love your passion. It's contagious.
What is physically special about that crystal that allows it to do this?
Nonlinear polarization density
@@girishk7003 Thanks!
Anharmonicity of ion-electron potential energy
"so thats it.. its so small..."
-physics girl to scientist guy
Thank you Dianna! Very interesting! Never knew how they entangled photons
i love how you bring such intense education to the masses. you rock. thank you.
Where did you get that beanie?!
Ukraine is watching you. I love your videos!
that's... kinda creepy.
Wut -_-
*Ukraine is watching you*
Vova Mint i know youre saying that people in ukraine watch your videos but it sounds like youre saying theyre spying on her. good job
Will Mint
Hahaha Very funny and acknowledged! lol Thumb up from Tamazgha land :)
I have to say that I enjoyed it. You have some talent passing that often complex knowledge in an easy way. Thanks and good luck! ;)
Brand New to the Show...Love it !! Keep up the Great Work !!
"It's so small!" - That's what she said.
wait...
Dejavu
She said that to you
yes we watched the video and saw her say that.
did you get the joke ?
Diana what would happen if a particle accelerator exploded? (Yes, I am talking about the Flash)
Frosty TheDoorman I dont think anything will explode during the collision of the particles as the tunnel is evacuated.
I meant if something went wrong or it was sabatoged
The worlds largest particle accelerator at the moment is the LHC under Genève. This machine is made to accelerate protons until they have each have an energy of 3,5*10^12 eV, about 5.6*10^-7 J. This isn't that much, however the LHC doesn't really accelerate protons but large groups of protons. I have been told that the combined energy of one of these clouds has a similar energy to that of a train driving at 150 km/h.
If somehow (like in an explosion) the electromagnets, which keep the group in orbit, stop working the beam of protons will go in a straight line trough the tube in which they are held (something like 0.5 meter of solid metal, liquid helium and some stuff for isolation) with little effort. After this it will crash in the wall and will be brought to a stop by the solid rock and concrete before it gets to the surface or to anyone who is nearby. However it is not just the direct beam that is dangerous. Every time a proton is slowed down it loses energy. This loss in energy will be turned into another particle. This can be a photon, other proton, electrons, and anti-mater or other stuff (maybe an higgs-particle). This radiation will most likely kill anyone close to the incident. (it would give you similar superpowers as eating some plutonium-210)
In case you are standing in the path of the beam it will burn straight trough you. If you are lucky you are hit in a none-vital part of the body and survive for some time. However you will soon die of the radiation.
lots of words that i do not know but I think I understand. However, I have a few questions. What is plutonium-210 and how can you get superpowers from it/particles/radiation?
@Frosty TheDoorman, I hope you are kidding... or a kid... or both.
Love your videos like this one, keep up the fun work.
It's so exhilarating to understand just a fraction of this stuff.
Why I confuse between Physics Girl and Brain Craft?
It's amazing that two of my most favourite people are both called Diana (Wonder woman if you didn't guess who I'm talking about). 😀
They must team up, maybe against Ultron.
another great video, Dianna! you are awesome. keep going!
Great video. Dianna has such a gift when it comes to teaching about things that she finds interesting. I see that Physics Girl hooked up with PBS, I hope that everything works out for her. And we can all continue to learn and share for years to come! What a wonderful and interesting world we have to explore!
if you were my physics teacher i wouldnt miss a day
Can you input two and get one out?
Yes, it is possible! It has to do with the size, structure, and angle of the crystal as compared to the wavelength of light. Dan's lab does exactly that. They send in two green photons, and they get out 1 ultraviolet photon.
How does that joining work? I can imagine each photon kicking electron to higher orbit, which then jumps two levels down emiting one photon of higher energy.... but does it work this way?
How precisely do they have to be timed and lined up?
It's the reverse of the splitting process. The crystal simultaneously absorbs two photons 'at the same point' then releases that energy via a transition that's twice the energy, producing the photon. This sort of thing happens all the time, for example you can shine microwaves on a metal, heating it so it emits IR radiation. This process is just more precise (And consequently harder to control.)
That unicorn seriously took me off guard.
X)
ffffffff real
Using this crystal for making the delayed choice quantum eraser.... It's amazing...
hi
+1 if you like the hat!
I just love Physics girl and the topics!Can't wait to see you hit 1 million subscribers!Many kisses from Greece!
"I don't belong here" jajaja classic. Great video
sorry I cudnt concentrate, physics girl is too cute. ahem..gotta focus!
I totally agree. She makes a lousy teacher as I'm completely mesmerised by her cuteness. I never hear a word she says :-)
Lew Minati ikr!
If this comment gets Physics girl's like, i will eat a live crab.
Edwin Graca only if i get her like( or 100 by others)
pi liked it!
+Physics Girl
PLEASE LIKE THIS
not even rounded
truncated
and guess what?
Sooooooo glad someone covers this now!!!
love this girl such passion makes me smile and learn at the same time .thank you
Your videos are so good, they are hilarious and interesting, thank you very much for your work.
Hi Dianna. I absolutely LOVE your channel and all your videos. Here's a little request: can you please make a video explaining how rattlebacks work? I could've looked it up on the Internet,of course, but it's just the way you explain, which makes learning easier and fun.
The way you’re describing the conservation of momentum and wave lengths needing to be precise sounds very similar to the required length of radio antennas need to be for emitting radio waves so they don’t burn out the radio.
nice to see an advanced physics simplified sort of video.. thank you for informing about edX can one get a degree from them
Dianna, not entirely related, but you should look up the 'sun stone' Vikings would use to help guide them and see the sun when it was cloudy. It was a crystal that would polarize the light. They would mark one side of it with a dot (tar, paint, or whatever) When they would look through the side opposite of the mark, they would see two dots. the dots would get closer together when they were closer to looking at the sun. And when they were looking at the sun, the dots would stack. This would help them navigate storms or clouds on the oceans.
The incoming photon is not absorbed into the crystal. That's the magic of these crystals. They can be used as amplifiers in a process called (optical parametric amplification) you can reach extrem amplification per unit length (1-10mio per mm). The crystal is just a catalyst and does not get hot. That's why this works at all. It's a really amazing process.
Oh and as a bonus you can amplify pretty much any wavelength longer than your pump wavelength. It's tunable.
Down conversion is the same process, without providing a second beam for amplification.
Really cool physics. I actually wrote my bachelor thesis about spontaneous-parametric down-conversion (SPDC). Nice to see a video about it! 😃
Frequency doubling crystals can be seen in green and violet LED laser pointers also, but getting uv is a little tougher!
A great article in wikipedia under "second harmonic generation" discusses this.
I was fascinated as a child with Iceland spar (calcite) crystals, which show double refraction visually...cheers.
Squeee! This is so cool!
I wish I had persued my physics dreams, but it is also kind of cool to see things like this happening :')
this channel is going to fill my offline video list so fast...
The finger unicorn had me dieing ... 😂😂😂
BBO crystals can also be used to make pretty awesome single photon at a time quantum eraser experiments by running the two photons through a Mach-Zender interferometer. It's almost more mind blowing than quantum delayed choice experiments, in that you can change the pattern in one optical path by placing components in different optical path.
I could hear fine. First, doesn't the air interfere with the photons? It is fun to see someone so excited about Physics.
Why isn't the crystal bbb?
As an undergrad in a lab the experimental Physicist said he was a poorly paid plumber.
Last year, I saw a talk at the MIT Science Museum about neutrinos. There are different kinds, but one topic was that a neutrino can throw off an electron. To my question about conservation of charge, he said that in another action, an electron merged back with the neutrino, so there was a net conservation of charge. Sounds like a good topic.
Finally, in addition to "spooky action at a distance," Einstein also said "God does not play dice with the universe."
Oh yes, some of you need a soap with mouth experiment.
Thank you Dianna for the great shows.
+Physics Girl 3:11 How? Even if you assume that the crystal and the whole setup is infinitely massive compared to the energy of a photon so that the energy lost in recoil is zero and there is no other energy loss, you can't send the 'daughter photons' in two different directions.
Because for a photon E = p*c (p = magnitude of a photon's momentum). So If the 'mother photon' had momentum (p1,0,0) and energy p1*c, the daughters have total x-momentum = p1 and energy p1*c. So the daughters leaving along x axis would satisfy the energy and momentum conservation. But if they also have (say) any y-momentum then the daughters will have more combined energy than the mother, violating the energy conservation.
And if the crystal recoils, matters become even worse.
Thanks Physics Girl. Dang, now you have me wondering if two entangled photons were each sent through separate Double Slit contraptions at the exact same time what the results might be. Thanks for the Video and for being so articulate. :)
This video was cool. There's a unique form of communications that can be done with this kind of tech.
Hi Physics Girl, a few vids ago you said that red shifted light due to universal expansion loses energy and violates conservation of energy. Is it possible that the energy is reabsorbed into space, which then powers dark energy? How could this be calculated?
we need more people with your enthusiasm in this field your fun to watch videos like yours maybe will help spark an interest to our younger generation. You take the nerd out of science. I love nerds too
Hi Diana! Love your vids! Where did you get that super awesome hat?
I would say the photon is not “split”, but that a tiny fraction of the energy (potential and kinetic) from the photon is captured by the crystal, and converted into a new photon once the captured energy is sufficient.
Can you recommend any good papers on parametric down conversion? Thanks.
I like the reference to the entanglement part but I would also like a reference video about how to produce two particles from one.
I rarely care about the sponsor but damn... Free online courses by MIT professors? That's beyond awesome!
So maybe the "trick" in entanglement problem is actually our creation process that define states? State is actually defined when we search for entangled particles and/or transport them to distances.
That would mean that entangled particles do not "communicate" with speed higher then light. They "communicate" way before actually measuring state.
so are the frequencies of the output photons pre-determined?.. that being said, is there a way of calculating the angle (or direction when it comes down to it) that the photon pair will be emitted from the bbo at?
Though SHG (second harmonic generation) requires a material to have specific molecular orientation in order for the incident light to be frequency doubled, some biological materials can be highly polarizable, and assemble into fairly ordered, large noncentrosymmetric structures. Biological materials such as collagen, microtubules, and muscle myosin can produce SHG signals.And I think since they have the X(2) susceptibility, also the reverse of SHG, the parametric fluorescence or how you call it SPDC or entangled photon pair generation. Using SHG imagining microscopy, they even made an image of collagen in liver. SHG is a nonlinear optical process in which two photons with the same frequency interact with a nonlinear material, are "combined", and generate a new photon with twice the energy of the initial photons
Hi Diana! Does parametric downconversion have possible implications for the possibility of instantaneous data transfer and ultra long distant communication?
That's so cool, she makes me understand things I wouldn't even care about in the future, and I love it!
1:17 when you are busy in something and someone asking you same question again and again.. 😂😂😂😂
If energy in = energy out regardless of going from 1 photon to 2, does that mean the 2 lost/split mass, lost speed energy, or what am I missing? Thx
Had to watch this a few times to get all of it. Fun stuff, also love beanie.
So, the way that the energy of one photo going in equals the energy of two going out is that the outgoing pair have a different wave length from the incoming?
A photon is basically a small packet of radio waves. Therefore, splitting one results in two with half the energy of the original, and in wave terms lower energy equals lower frequency, or longer wavelength. Or, combining two results in a shorter wavelength. Hence the color change.
Of course at the atomic scale all of these objects behave both like particles and like waves, and at the same time too.
Ian Macdonald a radio wave is a frequency on the electromagnetic spectrum, and the electromagnetic spectrum is sub atomically a bunch of massless particles, so your claim that photons are radio waves is therefor very misleading. A wave is just a type of motion, and therefor when people say that light is waves they really mean that a bunch of photons form an oscillatory pattern.
I just love see smart people talk! Thank :)
This is the birds-and-bees level of explanation as to how photons can multiply.
+Physics Girl -- I *love* the (relatively) new, a bit humorous, video style.
Physics Girl, great video as well as cool. Quick question if you so happen to come back here:
If the stream of entangled photons are directed at two similar objects such that some of the entangled photons gets absorbed by the objects atoms, with some entangled pairs gets absorbed by both objects - will this make the two objects become entangled or have entangled atoms vice just photons?
I didn't understand anything of it but somehow found it interesting
Really mind blowing explanation
What happens if you put the crystals in series? I mean, the "duplicated" photon from the first crystal is pointed to a second crystal, is there the same small chance to get again two photons?
Not if they're the same crystal; the crystal in question has two sets of states separated by one and two energy units. This allows it to absorb\emit light of one frequency and half that frequency only. So the crystal works only on a very limited range of light and cannot be used to 're-split' a split photon.
NO NO NO, you cant give us such an amazing video and rush through the explanation of how all of this occurs. Are these videos on a time constraint budget because if they are we can speak to youtube on your behalf
I love your videos! Glad to see science brought to general audiences in a market flooded with trivial nonsense
Great video Thanks! Question if you do not use a single photon but a 'beam' of light it works as well? I assume I remember the feldspar. Would it not be possible to modulate or ad a 'morse code' to one beam for instant communication? The crazy idea behind it is to arrest each beam on the Mars mission for example and then there use it for instant communication.
OH, OF COURSE this video is on your channel! Love the comedy, miss the physiks.
Omg hey I love your videos you make it so much fun to learn
Um I would like to know more about those vacuums energy fluctuations, that sounded interesting
That's basically the 'sea of virtual particles' that pop in and out of existence that people go on about. (The actual fluctuations are a better way of understanding it of course, but pop-in-and-out makes for a nice simple explanation.)
Thanks physics girl for dumbing it down
Great introductory video.
I sooo love these videos!!
whats it all for ?
so we can communicate instantly over long distances ?
When you say UV, my mind immediately goes to UV unwrapping... I play around with Blender too much :P
Solid state lasers have been doing 2xgreen to 1xUV conversion, third harmonic generation, for years. 351nm and 355nm pulsed lasers are two examples that use LBO crystals. BBOs can be used to do green to deep UV (~250nm) fourth harmonic conversion. She makes it sound so fancy lol