Why Quantum Computing Requires Quantum Cryptography

[@SophieSchmieg]

Cool video as always, but this time I have two comments: - The description of RSA contained a minor mistake, both factors have to be big (otherwise factoring is trivial in O(p) time, with p being the smaller factor). - The future of classical cryptography isn't quite as grim as the video makes it sound. There are several candidates for post quantum cryptography, based on lattices, hashes, and isogenies of supersingular curves. They are currently being standardized by NIST. The upside of these is that they do not require the transfer of quantum objects, which is a bit tricky, to say the least.

[@AdamJayS]

Add me on LinkedIn if you have it

[@williamwesner4268]

Would current fiber optic infrastructure not be capable of efficiently transmitting polarized photon packets?

[@SophieSchmieg]

@@williamwesner4268 I'm not an expert on fiber optic cables, as far as I know it's not that simple because you have to identify a single photon. On top of that you have switches between networks to deal with, where you'd need to somehow transport the quantum state from one wire to the next. Currently you go up the ISO stack at least a few layers to do so, which I can't see being possible with quantum objects.

[@Darkhunter190able]

​@@williamwesner4268you're not transmitting the actual photon here - you are transmitting information about the photon.

[@amihart9269]

The future of quantum cryptography is actually... nothing, it has no future. The BB84 protocol mentioned in the video can be trivially broken using a man-in-the-middle attack. It can only detect if someone observes a key in transit, but you can avoid ever observing a key in transit by the eavesdropper generating a second key which they can send to the recipient pretending to be the sender and receive another key from the sender by pretending to be the recipient. They would eavesdrop by decrypting the sender's messages with the sender's key and then re-encrypting them with their own key and sending that to the recipient. Not only is the BB84 protocol trivially broken and eavesdropping is possible, but even if it couldn't be broken, it still is not a good algorithm, because it does not actually _prevent_ a person from observing the key in transit, it only prevents communication if a person is observing the key. That means person could just intentionally observe the communication line in a sort of denial-of-service attack that would make communication on that line impossible. There is actually no solution to these problems. The Diffie-Hellman key exchange is well known to also be susceptible to a man-in-the-middle attack, but this is thwarted by combining it with a quantum digital signature algorithm. But it is provably impossible to construct a scalable quantum digital signature algorithm that would be at least as unbreakable as the quantum one-time pad (which it would be pointless to use quantum encryption if your key exchange algorithm is not at least as secure as it). The reason this is provably impossible is because quantum cryptography is centered around the No Cloning Theorem, but the No Cloning Theorem does not actually say you cannot clone qubits, but that you cannot derive enough information from a single qubit to then clone it. If you had millions of qubits in the same state, you could do statistical analysis on them and figure out their internal state, and then begin cloning them. Hence, the No Cloning Theorem would actually break down in any public key based cryptography since they rely on an arbitrary number of public keys being able to be distributed. The only documented quantum digital signature algorithm I'm aware of is the Gottesman-Chuang algorithm, but even they note in their own paper it is not scalable because the security declines the greater the number of copies of the public key are made.

[@entyropy3262]

That polarised filter stuff is very well explained.

[@bormisha]

It sounds so weird! I need to try it out with real polarization filters!

[@annoloki]

I don't think it is, the description of the filter is incomplete... it says what happens to light that passes through, but not the light that is "blocked"... this light is actually absorbed, and can be re-emitted by the crystals in the new orientation, which can constructively interfere with the light that passes through, which is why adding the middle filter means you get light pass through the third... at each stage, you're absorbing the light that won't get through, and re-emitting it at the new angle, so while you might get 50% of the light passing through, the amount of light that you detect the other side is more than 50%. A filter can't simply throw 50% of the energy away, energy must be conserved.

[@BadDogeU]

​@@annolokiThat's simply not true.

[@Xeridanus]

@@annoloki That energy conserved is usually transformed into heat, just like when light is absorbed by anything else. It doesn't have to be reemitted as light.

[@Cythil]

I do not find is such a hard concept to understand as long as one change perspective a bit.

[@tomareani512]

Quantum Internet, huh? I can see it now: "You might or might not have mail!"

[@perks6292]

"You've got or have not got mail!"

[@seventyfive7597]

Well, there are additional options, such as when you try to check the weather, but get mail, since you're checking for mail hence the weather report gets polarized to the mail axis.

[@togwam]

Tom Areani you may or may not be connected to the internet

[@Vasharan]

My news feed is already alarmingly polarized.

[@colleen9493]

More like, “you have mail and you also do not have mail”

[@EebstertheGreat]

2:15 In fact, both prime numbers p and q have to be very large. For optimal security, both should be of similar magnitude.

[@CrashM85]

Agreed, you also wouldn't exchange a "private key" under a bridge, you would exchange a "symmetric" under a bridge. No one other than yourself should ever know your private key.

[@fmaz1952]

Like 11 and 3?

[@Ceelvain]

Both should be very large, but not too close. Otherwise some methods would find the prime factors very quickly. Like the quadratic sieve IIRC.

[@EebstertheGreat]

​ F Maz With modern computers, we can sometimes handle even larger primes. @@Ceelvain Yes, in principle there are a lot of details you should follow for RSA, those just weren't details that came up in the video.

[@Halberdin]

@@CrashM85 The exchange would be of the respective public keys. They can also be transferred openly if they are signed by someone trustworthy (creating a certificate) or if the key fingerprint can be checked over a different, secure channel. Of course, symmetric keys can be shared under the bridge, too. But with a secure channel using RSA, this is not necessary. Symmetric encryption is used for the actual data because it is much faster.

[@warren286]

A secret rendezvous under the Einstein-Rosen Bridge 🤓

[@striker22343]

@Dog Ma Why are you being so rude to someone making a joke? They don't mean it literally, it's a play on words.

[@WWLinkMasterX]

"I got salty over an obvious joke so I'm SMART!"

[@chrisholdread174]

i literally LOL'ed

[@warren286]

@Michael Bishop you got me there! 🤓

[@zes3813]

wr

[@marie-helenemoreau5968]

Gilles Brassard the co-developer of BB84 is from my hometown! Fun fact: he started university at 13, got his bachelor's degree at 17, Master's at 20, and PhD at 24. He also helped develop quantum teleportation! A true genius.

[@taliastocks]

Slight correction: It is possible to have public-key security in a post-quantum computing world using classical computers, for example with lattice-based cryptography.

[@veggiet2009]

Go on...

[@Smerpyderp]

Go on...

[@vinlud]

en.wikipedia.org/wiki/Lattice-based_cryptography

[@ReaperUnreal]

I'm also a big fan of supersingular elliptic curve isogeny cryptography. There's a whole bunch of post-quantum classical encryption schemes.

[@mscheese000]

I think that's more than a slight correction. It refutes the entire premise of the video, although most of the information presented is still accurate. But yeah, there are definitely classical asymmetric encryption and key-exchange algorithms that are quantum resistant.

[@johnscott6072]

The Quantum Internet will have lots of Schrödinger's cat videos.

[@michaelworkman4057]

But the weird thing about schrodinger jokes is that they remain both funny and unfunny even after they are viewed >;

[@nandkumarzagade9583]

@@michaelworkman4057 woah

[@privateness.network]

that's the whole point of making it; memes and cat videos and I think (in 2018) Emercoin Randpay implemented enough radomness if used in that way actually allow QKD without any quantum computers

[@rufflefpv]

Quantum KZbin might or might not have dislikes

[@jaehoo_park]

With Quantum KZbin, you can view and not view a video.

[@_Killkor]

Me, trying to grasp cryptography: _this is difficult, to be honest_ Quantum cryptography: *hElLo tHeRe*

[@discomfort5760]

You encode using probability. Makes zero sense, but it works. Similar to how our Universe works, it just does.

[@Eric_Pham]

GeNeRaL kEnObI, yOu ArE a BoLd OnE

[@michaelcharlesthearchangel]

Super dense information/transformation/interformation is a difficult subject/project to comprehend. But quantum computer scrypts are meant to help us utilize quantum machine-human language, polysemiotic holographic lanGuage, in the easiest to understand method. So ya. H🤓llo tHere¡

[@firen777]

Quantum Cryptography: O̥̣͕̫b̷̼͖͓͎̟̤s͈̳̖͉̼͎̀e̯̻r̶v̙̠͓̯e͝

[@AURADRCalifornia]

Hey, I hear you. Me too🤔 keep learning PEACE-OUT

[@delson84]

Misleading on Internet security. I'll assume the physics is correct, but the security aspect is not. QC only breaks some public-key algorithms, not all. Yes, it breaks RSA. But we already have algorithms it doesn't break, and they don't need special quantum hardware to run; your phone can run them today. "Post-quantum cryptography" is the field that researches these algorithms.

[@PlasmaHH]

which ones are you referring to? even with elliptic curve you can use shors algorithm to break it

[@liquidluck711]

Thank you mork and micro for putting some real information out about cryptography. This video came across as a 5th grade level scare tactics to get younger generations to want quantum computing because of "muh privacy". We dont have privacy already and it's not like this Gov shill will mention that...there are still unbreakable codes used today that neither ai or quantum ai can predict. For them to be able to predict the keys would be to simulate massive amounts of raw irregular data and make sense of it. It cant. Atleast not in our lifetimes. Possibly our kids....

[@Fermion.]

@@liquidluck711Hmm, talking about "muh privacy" and government shills? This is a scientific channel; Alex Jones is that way ----> www.infowars.com/

[@delson84]

I don't follow this well enough to explain it; recommending "post-quantum cryptography" as a search term is the best I can do. From a security standpoint, the important thing is that the key sizes are larger (but not too much larger), and not all the algorithms are good at generating disposable session keys (a property called "forward secrecy"). But some are, and the researchers have time to find more. This media narrative "we need quantum tech for when the quantum computers factor our numbers" is popular, because it makes quantum computing sound more exciting. But it's unfair to the researchers finding new algorithms, and it scares the public unnecessarily.

[@liquidluck711]

@@Fermion. lmao except Alex Jones is a shill too. Science is not a democracy and popular vote should not rule what gets said and what doesnt. Looking into the past, look no further than Nikola Tesla who died penniless and a public joke, yet it was his patents which brought about the modern age. AC current, telecommunication devices, motors/generators, etc. Yet for some odd reason, he believed in aliens and was labeled a lunatic. This channel only tells you the surface level of popular science. And is gov funded (even tho they say viewers are the ones keeping the channel going)..I'll edit this comment with some links in a bit. Edit 1: TR3B Anti-Gravity Spacecraft - credible link: www.google.com/amp/s/www.military.com/video/aircraft/military-aircraft/tr-3b-aurora-anti-gravity-spacecrafts/2860314511001/amp Edit 2: Plasmoid vs Black hole? Idk, let's put it to a vote... kzbin.info/www/bejne/gGWxl5mKp8R6g80 Need more? I have a library full of truth, this channel doesnt even talk about 5% of what's real...

[@MrRolnicek]

Regular internet is full of misinformation. Let's ask the QUANTUM internet: Me: "Hey quantum internet, is this true or false?" QI: "Yes."

[@jogandsp]

Technically it’s correct though. The chance of your statement being true or false is 100%

[@MrRolnicek]

@@jogandsp I was referring to the phenomenon of quantum states being in superposition of both contradictory possibilities at the same time.

[@MrKelenek]

it might or might not

[@entyropy3262]

Truth does not exist, that is why the question cannot be answered correctly (or told in another way : with certainty).

[@lyrimetacurl0]

In a superposition it is true *and* false. (True *or* false means it's not in a superposition).

[@wntu4]

Quantum internet: When the pages load before you knew you were going there.

[@galgrunfeld9954]

Where the ad tunnels into your house

[@r7diego]

nice one !! 😂 😂 😂

[@elinope4745]

Already happens to me. Sometimes the KZbin algorithm is downright scary, and sometimes it is laughably wrong.

[@LuisAldamiz]

The page migh or not load. It may be this or that page. Wait, it sounds familiar...

[@Xackus]

Browsers can do this already

[@sogerc1]

Oh come on, no cryptography related example worth it's salt without Alice and Bob.

[@AmpDecay]

bringing back the pain that was intro to computer security class, only time i've ever had to use a long long int lol

[@TimLF]

Salt having 3 meanings

[@Vercingetorix525]

"Of course, you could just meet under a bridge" had me cracking up, I love it. The "metaphorical quantum mechanics bridge" follow up seemed kind of Vsauce-yish but with a touch of O'dowd to make it work. Watching new episodes of Space Time is always one of my favorite parts of the week. #O'dowd2020

[@austinglugla]

It is not necessarily true that all classical cryptographic ciphers will be compromised. There are many algorithms that will only have to adjust their properties in a post-quantum era. For example, symmetric key block ciphers(such as AES and Twofish) will only need to double their key size in order to remain secure against attack from Grover's Algorithm. By that same token, most hash functions will also remain secure with similar adjustments.

[@michaelsommers2356]

Why don't Albert and Niels just wait until the next Solvay Conference to meet and exchange keys?

[@terryboyer1342]

Because they're dead. Or not.

[@LuisAldamiz]

That would be too primitive, almost like using Cherokee translators instead of cryptography. Oops, they did it, it worked.

[@G0NZA11]

I miss PBS Infinite Series :( (at least we have 3blue1brown...)

[@g07denslicer]

What?? What happened to Infinite Series?

[@peterpiper6]

@@g07denslicer The guru, who was kissed by fire, left to conduct throrough research of the Banach space. Then they brough back the Sith Lord who used to host this show and we all know and love to fill the gap. Then the corporate tycoons decided to make the infinite series finite. Hope that clears things up!

[@G0NZA11]

@@g07denslicer kzbin.info/www/bejne/i3ran3alpt1sZ7M

[@paultapping9510]

Me too 😔

[@gabor6259]

Don't forget about the Mathologer.

[@alonamaloh]

"One of which is very large" [2:15] is not going to cut it. Trial division or [even better] Pollard's rho algorithm would crack the key very quickly if one of the primes is small.

[@benibachmann9274]

Correct, both should be large and of similar magnitude. The public key consists of the product of those two numbers and an exponent (e). This exponent can be small. Many implementations simply take 65537. Maybe the confusion comes from this fact.

[@LesMiserables10th]

"small" in this case means at least 1.340781e+154. Not exactly small, and that's just SHA 256.

[@lanvu9323]

I like watching videos about knowledge that I'm not capable to understand.

[@pflernak]

Hopeing something rubs off on you, aye. #MeToo

[@2hedz77]

I feel smarter...and dumber at the same time. Is that something to do with quantum superposition?

[@lanvu9323]

2Hedz maybe you just got quantum-ed

[@pflernak]

@@2hedz77 Its the intelligence uncertainty principle: "The greater the intelligence the larger the uncertainty in it."

[@2hedz77]

Haha nice

[@AFastidiousCuber]

To anyone interested in learning about quantum algorithms, I suggest reading "Quantum Algorithms via Linear Algebra: A Primer" by Richard J. Lipton and Kenneth W. Regan. If you've taken an introductory linear algebra class then you already know everything you need, the math is much nicer than you may think.

[@LunarDelta]

Too much bass and a huge suckout in the mids in the audio. New mic? Poorly mixed?

[@benw-l7k]

i think you've been smoking crack, sounds good to me

[@LunarDelta]

@@benw-l7k I'm not the only person to mention this, so I think you're either not experienced enough to hear it or just have shitty equipment.

[@geoffgordon5445]

Shut up and watch the video asshole

[@mikejones-vd3fg]

sound like a room effect, maybe they're in a new studio?

[@a64738]

It sounds really weird, like a some sort of distorted deep bass sound added to the voice. Think it muse be something wrong with the equipment somewhere, have heard something almost identical before on a laptop mic. You will probably on hear that effect on speakers that go deep in the bass.

[@traviscobbs]

While current public/private key algorithms aren't quantum safe, research is ongoing for non-quantum algorithms that will be safe from quantum computers. Take a look at "Post-quantum cryptography" on Wikipedia. So the advent of practical quantum computers does NOT necessitate quantum cryptography.

[@iainmackenzieUK]

Sound (and video?) quality seems a bit dicey. A second, best copy available??

[@thewavewarden3315]

yeah sounds like a hally studio to me

[@T33K3SS3LCH3N]

Yeah there is an annoying background sound throughout. Great episode otherwise but its a bit harder to listen to than normally.

[@nerdbot4446]

It's probably that Werner guy that messed with the soundwaves

[@iainmackenzieUK]

@@T33K3SS3LCH3N Maybe there is a "middleman" interrupting the communication... :)

[@AngDavies]

hmm, the background music seems a bit more lively than usual, or is that just me? maybe the compression is having trouble dealing with it+ his voice.

[@RobertQuattlebaum]

I'm not a physicist, but I do know a thing or two about cryptography, as well as a working understanding of quantum key exchange (QKE). The physics described in the video seem spot on, but the cryptography bits are highly misleading. QKE is not a viable way to address the security problems that will come from powerful quantum computers, for a variety of reasons: 1. Quantum computers don't break all existing cryptography. Symmetric encryption is weakened to effectively half of the key size. This problem is addressed by doubling the key size. 256 bit keys become the new normal, and yes, that is plenty. The mechanisms that Quantum computers completely break are the classical algorithms for authentication and key-exchange: RSA, ECC, etc. 2. QKE can only be used to secure the point-to-point links that have a high-quality "quantum channel" between them to facilitate the key exchange. This is typically requires line-of-sight or expensive wave-guides (like fiber-optics). Thus, QKE does not scale without "trusted repeaters", which can't be trusted by everyone. It also does nothing for authentication. 3. The industry is currently hard at work to develop quantum-hard asymmetric key-exchange and authentication algorithms to replace RSA and ECC. Indeed, quantum hard authentication mechanisms (like Merkle signatures) do already exist. QKE has its uses, but it doesn't address the real problems that quantum computers create. A "Quantum Internet", where planet-wide end-to-end switchable quantum channels are a reality, isn't likely physically possible. Even if it were, it just doesn't provide enough security over simply doubling the symmetric encryption key size and using quantum-hard classical key exchange methods.

[@alivateRocket]

Also - there are post-quantum cryptography algorithms, where there are no known methods to break the underlying mathematical problem by quantum or classic computer. One is based on "lattice". So the answer to the problem of "Quantum Computers" breaking the "Factorisation of Large Primes" problem doesn't require a "Quantum Internet" solution, a different unbroken mathematical basis with classical computers should also work.

[@acetate909]

Quantum internet huh? "I got your email and I didn't get your email" sounds like fun.

[@MrTomtomtest]

More like "I got your email and I am certain no one has read it"

[@ToxicTerrance]

"Certainty is irrelevant, resistance is futile."

[@acetate909]

@@MrTomtomtest I was making a super position joke. You're making a literal quantum cryptography statement. Awesome job on getting the point of the comment 👍

[@koenvandamme6901]

You won't know if you received the email until you check if your cat is dead.

[@michaelcharlesthearchangel]

The Neuronet, the near future & quantum encrypted/enciphered "quantum internet", is very vary v_ry hologram heavy and super dense. Much like the Matrix 4's screenplay and hypergraphic novel. On Facebook before Thanksgiving of 2020's release in theaters worldwide. :; facebook.com/The-Matrix-4-495972587598587/

[@charoleawood]

16:29 "At this point do we just give up trying to disprove the old man and just settle for the fact that it's probably all right?" Answer: NEVER!! I love this channel. Never stop never stopping, scientific inquiry! I am PASSIONATE about inquisition. I barely understand anything on this channel but I understand that and give a hearty Here Here!

[@jeffwilken7241]

Sounds like this wasn’t filmed at your typical location! Room reverb is boomy and gated. Fascinating content as always!

[@Megalomaniakaal]

mic broke?

[@jeffwilken7241]

Felix Kütt Sounds like a diff. room!

[@Megalomaniakaal]

@@jeffwilken7241 Might be moving the recording space/studio, so green screen temporarily set up in a random room with no sound proofing then? Now the real mystery is where are they moving?

[@jeffwilken7241]

Felix Kütt Hahaha indeed. Sounds like they’re in a superposition of studios.

[@Megalomaniakaal]

@@jeffwilken7241 It's a studio but also a watermelon?

[@EvenTheDogAgrees]

For those who don't understand one iota of the process, I had the same problem. So I had to look it up. This whole thing is not particularly complicated; here's a simpler explanation with some of the activities reshuffled for clarity. The first two steps are simply the creation, transmission and decoding of the bit string. 1) For each bit in a long string of bits, Albert picks a value (can be 1 or 0) and a basis (orthilinear or diagonal) through which to filter (encode) that value. This list of encoded values is sent to Niels. 2) Niels doesn't know which basis Albert used, so he has to guess as he decodes. On average, he will guess correctly about half the time. The next three steps throw away all the bits where Niels guessed wrong. Matt doesn't do this until much later, but these bits are useless anyway. So let's get rid of them now and reduce our cognitive load for the rest of the process. 3) Niels tells Albert which basis he used to decode each bit, but importantly: not which value he obtained. 4) Next, Albert compares Niels' choices to his own, and tells Niels where he guessed correctly. 5) Both parties now know which bits can be discarded since they would decode randomly anyway. After discarding them, they're left with about 50% of the bits in the sequence, since Niels guessed correctly about 50% of the time. Of all of these remaining bits, one thing is known for certain: if nobody was eavesdropping, both Albert and Niels should have the same values for them. Now we verify confidentiality of the photon communication. For this, some bits are sacrificed. 6) Albert and Niels decide on a subset of bits to compare amongst each other, and see if they match up. If the communication has been tampered with, odds of all bits decoding correctly are astronomically small since Heisenberg also had to guess, and only guessed correctly about half the time. So if we see anything other than a perfect 100% match for these randomly chosen bits, we know something's up. Finally, we can construct our key. 7) The key is simply the sequence of values for the remaining bits, after we've removed the sacrificial ones. Of these remaining bits, we know that the values have never been transmitted in the clear. They are known to both Albert and Niels, but nobody else. Sidenote: Matt doesn't remove the sacrificial bits from the key. And strictly speaking, it's not necessary. But their values have been transmitted over an open channel, so they may have been overheard. A key of 100 bits is exactly as strong as a key of 200 bits if the position and value of 100 out of those 200 bits in the second key are known. But the key takes up twice as much space, so there's no incentive to keep the 100 known bits around. Oh, and here's a list of errors I found in the animations. I may have missed some, so feel free to add to the list. 7:50 - Albert's second to last diagonal points in the wrong direction. 8:07 - Niels' diagonal points in the wrong direction. 9:14 - Werner's sixth diagonal points in the wrong direction. 9:24 Again, Niels' first diagonal points in the wrong direction for the value it decodes to. The problem I had with this video is that the narrative structure was quite confusing and made things more complicated than they need to be. The fact that Matt is a fast speaker, and that you're trying to interpret the complex matter he's presenting while simultaneously trying to interpret the fast moving visuals, _which in turn contain text as well_ that competes with Matt's voice for the same set of neurons that's responsible for decoding language, doesn't help. Yeah, as much as I appreciate how these guys and girls are trying to bring some intellect to KZbin, I sometimes wonder whether disseminating knowledge is actually anywhere on their list of priorities.

[@nexusvoid314]

Ha! Jokes on you, my internet history is all past episodes of Spacetime

[@FirstRisingSouI]

Hmm, interesting, it doesn't seem to go back before a few hours ago. . . .

[@nexusvoid314]

@@FirstRisingSouI *Laughs nervously* pff, well yeah I only discovered the internet a few hours ago

[@FirstRisingSouI]

@@nexusvoid314 Sure. That makes sense. *winks*

[@gotenks222]

This is the first video i watched after discovering the internet

[@atrumluminarium]

9:32 that's not a man-in-the-middle attack that's intercept-resend. BB84 cannot detect MitM but E91 can *Edit for clarification:* A MitM attack involves severing the AB connection entirely and setting up two distinct connections AE and EB and E pretends to be the other party to both of them. As far as A is concerned, she is talking to B and as far as B is concerned he is talking to A.

[@annachow4631]

No, I'm pretty sure it's a man-in-the-middle attack. In order to perform an "attack," the original message (or key) must be manipulated; not just observed. Now if the point is detecting an eavesdropper, then I agree that BB84 won't work for that, but entanglement-based encryption will.

[@atrumluminarium]

@@annachow4631 A MitM attack involves severing the AB connection entirely and setting up two distinct connections AE and EB and E pretends to be the other party to both of them. As far as A is concerned, she is talking to B and as far as B is concerned he is talking to A. E91 "solves" this by making the system symmetric between A and B and leaving the pair production to a third party. That way E would need to own her own (potentially expensive) equipment to carry out the attack undetected thus providing a barrier to entry

[@bogdanieczezbyszka6538]

But isn’t that the whole point of quantum messaging that even reading the message changes it? What am I missing here?

[@atrumluminarium]

@@bogdanieczezbyszka6538 it's the key that is being generated quantum mechanically. The message encryptions and transmissions are done as they already are in a "classical" way.

[@delsquaredphysics2897]

This is true

[@briancrane7634]

Best explanation of the 'sunglasses-lens' experiment that I've heard...thanks!

[@yuvalne]

Veritasium and 3b1b have a wonderful collab about the quantum filter experiment in minute 7.

[@Tondadrd]

Forgot to clear the audio by Audacity? It really hurts my attention.

[@uint16_t]

Sounds like compression artifacts

[@trelligan42]

Or the background music got blended in somehow. 1:34 "Classical".

[@3ATIVE]

Did you change your audio setup?? Your voice is way Bass-y-er now.

[@fatmn]

Their productions techniques seem to vary greatly every week when it comes to lighting and audio.

[@alejandromartinezmontes6700]

I think it's missing EQ and compression.

[@mikejones-vd3fg]

@@alejandromartinezmontes6700 I think its a room effect, like they're in a larger room or something, hmmm, the mystery continues, is there anyway to test these hypothesis'es? We could train a neural network to process all the videos audio data and find out what happened, id imagine a quantum computer powered nueral network would definately figure it out.

[@MrSomeSkeptic]

Dude, I thought I was just really high. Thanks.

[@sarcasmo57]

My darling I.... can't get enough of you love baby.

[@alanlee1355]

I love this channel even though i can't understand most of it half the time. 👍

[@caixiuying8901]

lucky for you, I can't understand half of it most of the time

[@samsonsliteye]

audio quality for this video sucks, what happened?

[@TylerMatthewHarris]

PBS needs to bring Infinite Series back :(

[@zes3813]

wrr, happyx nmw

[@disgruntledwookie369]

Btw if anyone wants to try the experiment with the polarising filters, you don't really need 3 of them, you can use a PC monitor or TV as the light source. This light is already polarised. In fact, I noticed this weird quantum behaviour myself not long ago after buying a pack of polarising filters (I'm just a nerd). If you hold one filter up to the screen and turn it until no light gets through, you can then take another filter and place it behind the first one. As you rotate the new filter, you will see some amount of light coming through, which really is quite surprising when you first see it. I was puzzled, and immediately began trying to explain my observations, ultimately drawing on some quantum physics lectures from half a life time ago. I was reminded of the way electron spin works when measured (really the similarity between these experiments is no coincidence). If you measure an electron spin to be "up", then you will never afterwards find it "down". That is, unless you measure it again on a different axis, forcing the spin to collapse into one of the new eigenstates. Following this, there is a non-zero probability that the electron will be measured "down" in the initial axes. I might have butchered that explanation a bit, but the principle is the same as we see here with polarised light. It is a fundamentally quantum phenomenon, yet you can see it in your own home for the cost of a couple of polarising filters (pennies)

[@filipsperl]

I suggest watching Veritasium's video on these quantum filters, it really helped me understand this one

[@r7diego]

For me was the oposite: this video clarified me some obscure stuff from Veritasium ... both are great !!

[@trinitygoldmedia]

LMAO!! Thank you for that delivery.. Your humor @16:23 reminded me of Feynman discussing Cavendish, "Determining the constant of the gravitation equation... Weighing the Earth!!!". Your series is amazingly educational, humorous and just down right addicting! smh. Can't wait for the next one!

[@andysantarelli3056]

I just watched the entirety of the Quantum Mechanics Learning Playlist on this channel, and all the way up to now I've felt mostly comfortable in understanding the contents, even if it took me a bit. This one was a doozy for some reason though, much more difficult to wrap my head around.

[@universaltravellers7906]

Nope, he I understand QP and Cryptography very well and I can tell you that he didn't this wasn’t his best work

[@MaddGameMaker]

It's not true that "even the most sophisticated classical security systems will be compromised". There are classical algorithms which are secure against quantum computers, such as Ring Learning With Errors.

[@-sui-]

As someone who does cryptography as his day job this video made me seriously cringe. Quantum computing does break RSA (and Elliptic Curve Cryptography and Diffie-Hellman based systems), but the obvious solution to this is not quantum cryptography. Instead we would switch to quantum-resistant cryptosystems such as NTRU which are basically drop-in replacements for the systems which get broken by quantum computing. Even though those admittedly come with a hefty performance penalty this is only an issue for the connection establishment as the actual data encryption is never done with public key cryptography but rather with symmetric cryptography for which a key is agree upon using public key cryptography. But most notably symmetric cryptography (such as AES) is not broken by quantum computing at all. The summary starting at 13:16 is false. You do not need a quantum internet for security in a post quantum computer age because quantum computing resistant public key cryptography is already available.

[@dalebewan]

水 -sui- Thank you. Was about to try to explain all that myself, but you beat me to it.

[@PappLacc]

What was wrong with the audio? It's a bit weird this time. New Mic. perhaps?

[@mertk.2376]

I think this audio is outright disturbing. I had to go watch an older video to calm myself after hearing this.

[@kyjo72682]

too much bass

[@ploppyploppy]

They've had this before. It's due to the audio being overcompressed to achieve a uniform loudness. It's really quite an amateur home recording mistake so I can only think either they are skimping on the editing wage or their resident editor is not well :)

[@cmilkau]

2:20 You definitely need to ensure that at least TWO prime factors are large. All small prime factors are easy to find and provide virtually no benefit for the extra cost. If you have all but one prime factor, finding the remaining factor is trivial.

[@SvenLeuschner1]

how you weave "Spacetime" at the end of every video is magical

[@willisverynice]

When people ask what I do with my physics degree, I tell them that I am able to watch PBS space time videos without having to go back and watch all the lead in videos first.

[@christopherthomas9541]

I love this show!! Sometimes I leave with a headache and having to re-watch it lol, but I love it!! Great job!!

[@lloydchildress9239]

You lost me at 3:08 falls apart...or did you gain me back on the uncertainty principle, yes I'm certain.

[@MusicalRaichu]

I think I only lasted a few seconds longer than you ... maybe we're entangled or something.

[@JoshuaHillerup]

We won't need quantum cryptography to resist against quantum computers. There's a ton of classical cryptography algorithms out there that also can't be cracked by quantum computers, although you're right that the most popular algorithms are vulnerable. But switching our encryption libraries/protocols is a lot easier/cheaper than setting up these quantum computer setups, since no new hardware is needed.

[@jeanvincent4764]

Yet quantum cryptography would be very cool. The main issue I see is that quantum cryptography might be very hard to implement end-to-end, say in everyone's smart phone.

[@JoshuaHillerup]

@John T why? Encryption has to be end to end to work.

[@JoshuaHillerup]

@John T what do I do about evesdropping along A-K and N-Z?

[@JoshuaHillerup]

@John T huh?

[@louis-philip]

New production team? Sound and image have been a bit off for the last few episodes compared to what it was. Anyway, always good content though!

[@mykulpierce]

Very nice to see this concept being developed more fully.

[@hiqwertyhi]

oh no the ridiculous audio compression is back...

[@da1otta]

Yeah, Matt sounds slightly drunk because of it.

[@danielyount9812]

Excellent topic of quantum encryption(One of my favorites). With IBM and Google and even Canadian company D-wave, the Quantum computer for everyday use use is quickly becoming a reality. Knowing how to protect its data and what to watch out for and when to completely discontinue classical encryption methods.

[@philippvoid1800]

heatdeath is coming... still a better story than winter is coming

[@the1exnay]

Is there a difference? The heat death will probably be rather cold

[@tehguitarque]

(1) Thank you for being someone who finally explains the 3rd polarization phenomena! I've never heard a fundamental explanation before.. (2) You... and I've noticed this from the start.. use Star Trek SFX. Where'd you get them all? wav files from a bunch of old ST games? That's the only place I've found them! My inner child must know!

[@JWhittskey]

new mic? The EQ sounds off on all of the dialog

[@Stabacs]

Justin Whittenberg monolog

[@xenorac]

Thank You! I thought it was my hearing!

[@MrSchrodingersCat01]

While Quantum computing is interesting, it is important to understand that no practical quantum computer currently exists. In fact, quantum computing may not be practical in the foreseeable future. That is quite a claim, but this article explains it better. spectrum.ieee.org/computing/hardware/the-case-against-quantum-computing

[@pij3333]

As as cryptography nerd I felt voilated when you switched out Alice and Bob. Also, really interested in hearing about how they solve packet routing when sending quantum bits over the internet without breaking the entaglement

[@kevinr7216]

Bruh ive been watching your vids for years nonstop, and ive never asked this, HOW DO YOU KNOW SO MUCH.....

[@MegaRabbitPower]

Did you guys just cover the Triple Polarizer Paradox off-handedly without an episode to cover how it implies there's potentially no such thing as free will? For shame.

[@FineFlu]

I’ve come to appreciate the craftsmanship in these videos. Well done

[@artemZinn]

PhD in Quantum Mechanics Voice: **IM IN**

[@pierreabbat6157]

Actually, there are three independent ways the polarization can be measured: orthogonal, diagonal, and circular. Circular polarization is fundamental, as the two states are the same as the signs of the photon's spin; orthogonal and diagonal polarizations are superpositions of two circular polarizations with different phase differences.

[@danfg7215]

I’m now in a superposition of understanding and not understanding this video 🤔

[@cleemcnabb2363]

It's fine the only difference in you and them is they know how to do the math for what they are also in a superposition of understanding and not understanding.

[@Practicalinvestments]

I now collapse the wave function by pointing out that if you understood the video, then you couldn’t ’not understand’ therefore: you don’t understand the video

[@eddyestevez500]

I can imagine how hard it is to write these episodes. Adapt the technical text in way that is understandable by the general public AND do not sacrifice the accuracy of the concepts.

[@TheLevano22]

Internet, where you can find Joe Jonas explaining Quantum Physics to you.

[@wesleyrm76]

I like this much more than the Peter Dinklage comparisons

[@Hisu0]

Cavemen.

[@ananths5905]

As a computer science student and now developer just thinking that computing hasn't changed much in the last many years this video was very interesting

[@DingoDjango]

You might be interested in a video titled "Quantum Computing for Computer Scientists" on the Microsoft Research channel

[@fzigunov]

The problem with quantum internet is that we still have to invent quantum modems... (Not kidding, if cryptography is physics-based instead of math-based, how to handle sending unaltered pairs of photons over very long distances across multiple switches and servers? How to handle traffic from multiple clients?)

[@kukulroukul4698]

just throw a shovel of coal in the system

[@kaitlyn__L]

Totally. The existing functional experiments send the quanta directly. There's a lot to go into making this functional.

[@HakaiKaien]

Personal quantum computer may be off the table for a very long time but I strongly urge people with the necesary resources to invest massively in this technology. Just a few stable quantum computers, with a few thousand qubits will change the world

[@osmosisjones4912]

Negative mass asentally is the flow of Mass. Away from heavy bodies as a pose to towards. When molecles are excelurared .they get denser. And some energy should get released. As your ship gets faster

[@paramountx]

Lol I've seen Matt a few times in NYC. First time he gave me that look that was like "yeah, I am that person" when I was glancing. The second time he was in a rush and I don't think he had time to talk. Either way; my hero

[@tinymidged]

What do you use as background music, its soo relaxing!

[@soliddanii]

The background music at the end during the comments is from "sine wave digital" (radio station from the game: the crew)

[@tinymidged]

Thanks for the answer :).

[@mynameisZhenyaArt_]

2:06, NO, it is called PSK (Pre-Shared KEY). Also, We not only use RSA, but Diffie-Hellman alg. as well, combined with AES most often...

[@samirm]

You can have quantum resistant classical cryptography though...

[@sethgrasse9082]

Great video on quantum cryptography. In case anyone's wondering, the mathematics of how quantum computing beats classical cryptography is very well explained in MinutePhysics.

[@Thee_Sinner]

_Infinite Series_ was a finite series.

[@petersinclair3997]

Uriah Siner .... Well depend how many times a finite series be divided? Zeno would fun, here.

[@johnransom9983]

I have played around with the IBM publicly available quantum computer. I want to point out something in the FAQ. "Superposition is strictly weaker than full parallelism, and strictly stronger than probabilism." You can find this at quantumexperience.ng.bluemix.net/qx/tutorial?sectionId=beginners-guide&page=000-FAQ_for_Beginners~2F001-FAQ_for_Beginners. You and others frequently say that because of superposition that it can do multiple computations at once. That is incorrect from my experience of playing around with it. Ordinary computers already have full parallelism and therefore that is not how quantum computers will be faster. It is the entanglement property that will give them an advantage but only in certain types of calculations. Otherwise conventional computing will be faster.

[@KohuGaly]

ordinary computers do not have full parallelism. Their parallelism is limited by the number of physical circuits that you connect in parallel. Whenever you have a problem that can be beaten by full parallelism, you can still make it practically unsolvable, by ramping up the parallel paths necessary to solve it quickly. Quantum computers technically can compute multiple things at once, but you can actually read out only one of the results randomly. Superposition allows you to cancel out the "wrong answers" so you only read the right ones. It only works in some special cases, which is why QC is weaker than parallel computing.

[@tutoringwestern4970]

I think we need two videos next week to make up for this late one with bad audio.

[@XEinstein]

This was the first PBS Space Time video that I actually didn't find that interesting. Normally, any PBS-ST upload is a highlight of my weekend. I guess I'm becoming spoiled with all the wonderful content this channels normally delivers.

[@charlesrosenbauer3135]

Or we could just use Quantum-Resistant Cryptography like NTRU.

[@octoman_games]

Like IOHK and Cardano are using

[@ThueJanusKristensen]

The impractical key you exchange under a bridge would be called a "symmetric key" or "shared secret". A "private key" (the term you used) is one half of an asymmetric key pair as used in e.g. RSA.

[@joshderr]

Thanks for the video, and for reminding me that Infinite Series was awesome but is also no more :(

[@veggiet2009]

I really miss infinite series, I it was my favorite of pbs shows

[@nafrost2787]

6:50 Are you sure that this is because of the Heisenberg uncertainty principle? I thought it is because in quantum mechanics only certain quantized values are allowed.

[@randycarvalho468]

Wtf is with the audio in this? Sound like Max Headroom.

[@madscientistshusta]

Thnx for using niels bohr, i never get to see enough bohr rep in these science channels and he's kinda my hero.

[@freezybut]

3:46 what would you do if we kissed under the metaphorical quantum mechanical bridge?? ☺️😍👀

[@Belodri]

Since you know where you were, you wouldn't know if you had kissed or not.

[@PeterB12345]

Or you knew you kissed but had no idea where!

[@DaKoopaKing]

ZOOMERS OUT

[@AndrewKay]

"Choose two prime numbers, one of which is very large, multiply them together to get an even larger number, and broadcast that as your public key" They both have to be large! The smaller the factors are, the easier they are to find by trial division. Generally, both prime numbers are chosen on the same order of magnitude. Not just for security - the RSA encryption and decryption processes only work when the message is coprime to the public key, so if it has a small factor then there's a non-negligible chance of a message sharing this factor and being undecryptable. It's also just more efficient to generate e.g. a 2048-bit key by finding two 1024-bit primes than it is to generate a 2000-bit prime and a 48-bit prime, because primality-testing algorithms are much worse than linear complexity in the number of bits.

[@S.R.400]

Thanks for the reminder.. RIP Infinite Series:(

[@BlueZirnitra]

I only learned of it from this video and just subscribed, what happened to it?

[@andrewxc1335]

Ran out of funding vs. the size of the audience. It was pretty sad.

[@mentalchillnesss]

F for finite. The universe would give us another paradox by making the Infinite Series so short, so finite, wouldn't it?

[@feynstein1004]

@andrewxc1335 That's a shame. But I guess I can understand. I myself unsubscribed a long time ago. Not because the content wasn't good, but because I just didn't find pure mathematics very interesting.

[@frankschneider6156]

Ben McCann The original (and very good) host of infinite series stopped, to get her PhD done, and the guy they hired to replace her (who was also the former SpaceTime host, before Matt took over) sunk the show to a level that was unwatchable, so the show went pretty fast belly up thereafter. That guy also nearly sunk SpaceTime, and it just became good after Matt took over. Initially they had videos about farting astronauts and such stuff (no joke, but sad truth).

[@bugsdelany]

will definitely watch this episode at least 2 times before it starts to make proper sense

[@DrakiniteOfficial]

Gosh, what happened to the audio?

[@Sagivbh]

I found this channel now!! insane. best channel of physics in the world!

[@pat151uk]

I thumbed up before I even pressed play!

[@LeoMindedSage]

As you should

[@damjanpecijareski2088]

I actually have quantum information processing in my 6 semester love this video❤

[@kayvee256]

Have you had The Talk? www.smbc-comics.com/comic/the-talk-3

[@estudiordl]

"Do You Guys Just Put The Word 'Quantum' In Front Of Everything?" Antman, 2018.

[@BlueZirnitra]

I take it that movie isn't very funny?

[@kailomonkey]

@@BlueZirnitra I love quantum physics and I love Antman movies... Although they stretched what is actually possible with quantum understanding a bit too far in Endgame...

[@YoungTheFish]

@@kailomonkey it almost feels like 1960s pulp sci fi logic tbh

[@VerthNeel]

And the Wasp.(the prettiest part of it)

[@Sam_on_YouTube]

The PBS Infinite Series video was fine, and they were produced by the same studio that makes your show, but 3 Blue 1 Brown was a lot better.

[@jdtug8251]

Your audio sounds distorted by the gravitational pull of a nearby black hole.

[@vadymzayets6401]

The example with polarizers is a simple trick. In this case, there are 4 independent optical data transmission channels (2 polarizations*( phase + amplitude)). Even a simplest multi-channel encryption is practically unbreakable. There are millions of reliable and unbreakable encryption methods, which do nothing with the Quantum Mechanics. One of oldest one is the synchronized oscillators. The simplified version of which is a random-number generator, which is synchronized to the year time or the day time of an event of the user. If I recall correctly, none of the “powerful governments” was able to break even a relatively- simple Skype encryption. Of course, one, who has the encryption key, will be always able to break any encryption. It is because another powerful QM rule of “Uncertainty of the user”. In the case when the user does not have a distinguish feature (like a biological feature), any hacker with the correct encryption key can break the code. The Quantum Mechanics cannot help. Bureaucrats from science love the words “Quantum Computer” and “Quantum Encryption”. This is a common case when a good fancy name is sufficient to pump some money from government.

[@terryboyer1342]

The Heisenberg Uncertainty Principle. I'm not sure what I think about that.

[@colleen9493]

You can never know for sure...

[@kevinocta9716]

You're wrong. My history IS just episodes of PBS Space Time! (Cause it's so damn good, that it's the only show i need!)