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Michael Nielsen's Free Video Courseware On Quantum Computing

Soulskill posted more than 2 years ago | from the superposition-of-knowledge dept.

Education 54

New submitter quax writes "Michael Nielsen, who co-authored the book on Quantum Computing, released a set of short video lectures on his blog this summer (link to Google cache). They make a great introduction to the subject. But here's the catch: Due to other work responsibilities, he stopped short of completing the course, and will only complete it if he sees enough interest in the videos. Let's show him some numbers."

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54 comments

ENOUGH with the lies! (0)

Anonymous Coward | more than 2 years ago | (#37578986)

Okay. First of all, I am a highly qualified individual who has acquired an online degree in chemical mathematics again. The truth of the matter is that the summary is not only wrong, but it fails to mention that quantum computing is not stargazer. It is pew pew along the lines of magazine.

Sorry I came to the garbage of this place and realized it.

Re:ENOUGH with the lies! (1)

gilleain (1310105) | more than 2 years ago | (#37579518)

Interesting. Please, tell me, what area of chemical mathematics tells you that quantum computing is ... er ... "not stargazer". Whatever that means.

Re:ENOUGH with the lies! (0)

Anonymous Coward | more than 2 years ago | (#37579910)

I'm a highly certified individual with an online degree in chemical mathematics again. I can tell you that, without a doubt, quantum computing is false. Where is it?

The truth hurts. That's why your scourning parading is matched. No more truly will away!

Re:ENOUGH with the lies! (1)

Osgeld (1900440) | more than 2 years ago | (#37580214)

just ignore the whatever, they have posted this exact same comment on other threads, which has nothing to do with chemical mathematics, its just some spamdouche

Re:ENOUGH with the lies! (1)

gilleain (1310105) | more than 2 years ago | (#37580284)

just ignore the whatever, they have posted this exact same comment on other threads, which has nothing to do with chemical mathematics, its just some spamdouche

Yeah, found them : http://slashdot.org/~ThatCopyrightMadow [slashdot.org]

Weird. It's like spam, but also like a high troll. Oh well.

Re:ENOUGH with the lies! (1)

SomePgmr (2021234) | more than 2 years ago | (#37583446)

It does seem automated, though I wonder if it's someone testing something. Maybe to see if a script can build karma or something? I don't see any product links...

Too bad the replies are mostly variations on the same few words and it comes out sounding like some nonsensical babelfish translation.

Preemptive (0)

Anonymous Coward | more than 2 years ago | (#37579024)

Let's have this post as a placeholder for all the Heisenberg and Schrodinger superposition jokes that show up in every single quantum computer story. Thanks!

Re:Preemptive (1)

Ardeaem (625311) | more than 2 years ago | (#37579380)

Let's have this post as a placeholder for all the Heisenberg and Schrodinger superposition jokes that show up in every single quantum computer story. Thanks!

Do you want the jokes or not? You can't have it both ways.

Re:Preemptive (4, Funny)

maxwell demon (590494) | more than 2 years ago | (#37579436)

Let's have this post as a placeholder for all the Heisenberg and Schrodinger superposition jokes that show up in every single quantum computer story. Thanks!

Do you want the jokes or not? You can't have it both ways.

In quantum mechanics, you can. But only as long as you don't look.

Pun warning (0)

Anonymous Coward | more than 2 years ago | (#37579102)

Don't be the one who Niels in front of Bohr-ing subjects and plow through.

My mistake (2)

bp2179 (765697) | more than 2 years ago | (#37579178)

I misread and thought that said Mike Nelson. Got excited about a Rifftrax about quantum computing.

Re:My mistake (1)

type40 (310531) | more than 2 years ago | (#37579970)

I was expecting the lectures to be taught by Gypsy with color commentary by Crow and Tom Servo.

Sigh in, pass through two H gates, sigh out (0)

Anonymous Coward | more than 2 years ago | (#37579330)

That's my notes from lecture 4. As you'd expect, they're simple and complex at the same time.

The next major revolution will be quantum..... (1)

Desmoden (221564) | more than 2 years ago | (#37579350)

For me, a major fundamental revolution is one that goes beyond improving on itself. A concept or group of concepts that begins and in the end permeates nearly every product and concept throughout the human world.

We are very much into the run of the "Information" or "Computer" or "Digital" revolution in how people are now in mass looking at every single mundane product or process and seeing how this "new" way of looking at things can change/improve/simplify. Evidenced by the Refrigerator with Ethernet port, TCP/IP stack and webserver.

Quantum, or more specifically quantum mechanics will be the next Major human revolution.

Once pure quantum systems are produced and seen to have value we will see an explosion of devices, products, processes.

You will have Quantum Disk Suite, a way of linking drives together so that backups aren't needed.

and Quantum Transceivers to that all those Optical SFPs in your switches and routers won't need cables anymore

and Quantum Video technology so you don't see that lame bloody delay when someone from NY is talking to someone on TV from Paris.

When? Very hard to tell. It will however, just as Industry and 0's&1's did before, change _everything_

Re:The next major revolution will be quantum..... (4, Informative)

JoshuaZ (1134087) | more than 2 years ago | (#37579480)

I don't know if you are serious or joking here, but you could definitely stand to take this course. You seem to be under a lot of misconceptions about what quantum computing can do.

Quantum, or more specifically quantum mechanics will be the next Major human revolution.

Quantum mechanics is used all the time by lots of devices you use. Small transistors work because of quantum mechanics. Lasers work off of lots of quantum mechanics. LEDs work off of quantum mechanics. Etc. Etc. There's nothing new about using quantum mechanics.

and Quantum Transceivers to that all those Optical SFPs in your switches and routers won't need cables anymore

This and almost every other application you mention is complete nonsense. Quantum mechanics does not allow you to transmit information in special ways. Entanglement doesn't let you get away with that. (This is as far as we are aware, ignoring for now certain very interesting results from CERN that are likely to be incorrect and are still being checked over. Even if this is correct, it is unlikely to allow actual FTL or the like but rather be other interesting new physics. And calling that simply quantum mechanics would be misleading.)

You can do things with quantum computers that you can't do with conventional systems. What we mean by quantum computers are not computers that use quantum mechanics in general (since they all do that) but computers that can take advantage of entanglement. This allows certain processes to occur much faster than they can with a conventional computer. For example, operations with Fourier series become a lot easier, and it becomes much easier to find the period of a given function. This translates into being able to do certain classes of problems much faster.

For example, it seems that using something called Shore's algorithm ahref=http://en.wikipedia.org/wiki/Shor's_algorithmrel=url2html-18175 [slashdot.org] http://en.wikipedia.org/wiki/Shor's_algorithm> you can factor integers faster on a quantum computer than you can on a classical computer. This is a big deal, but even this requires a lot of caveats. First, we can't actually prove that this is better than the best classical factoring algorithms. In most interesting formulations of this claim, it depends on the assumption that factoring is not in P, a claim that is strictly stronger than the claim that P != NP http://en.wikipedia.org/wiki/P_versus_NP_problem [wikipedia.org] (it is possible that factoring lies in P but one gets a large speedup of like Klogn or something like that to the quantum system. This is possible, but fundamentally less interesting and less useful.)

There are other specific similar examples, and even a handful where we can prove that the quantum version is really better than any classical version. The most prominent such example is Grover's algorithm. http://en.wikipedia.org/wiki/Grover's_algorithm [wikipedia.org] . This algorithm allows you to search unsorted databases much faster than you can in a conventional setting. That's a really useful but ultimately high restrictive use.

Now, in fairness to you there are some uses of entanglement and other interesting quantum phenomena which don't rely on quantum computing per se. So you may have been thinking of those. But those don't allow what you seem to think they can do either! The closest to anything like that is quantum encryption, which makes a system of encryption that is essentially unbreakable as long as our understanding of the laws of physics are correct. That's pretty cool but even that has its own limitations, and it turns out can in some specific circumstances be broken http://www.sciencedaily.com/releases/2008/05/080508143107.htm [sciencedaily.com] . There are other interesting technologies out there like so-called "quantum dots" that are turning out to be quite useful. But they aren't much more quantumy than lots of other stuff.

So no, quantum mechanics isn't going to change everything except in so far as it already is used in all sorts of technologies you use in a daily basis. And it isn't going to allow instantaneous communication without any form of physical connection or anything like that. That's too bad, because everything you mention would be awesome. But nature doesn't work off of what is awesome so engineers and physicists need to build awesome things that actually fit the laws of physics.

Re:The next major revolution will be quantum..... (1)

Desmoden (221564) | more than 2 years ago | (#37580402)

WOW! Here I was just relaxing on a Saturday morning imagining all the crazy possibilities if we end up being able to transmit state without any consideration of distance. Quantum computing as described in these great vids is just one example of how things can change.

Personally, I don't believe in impossible. Between the Easter Bunny, Santa Clause and now the Speed of Light, I've learned not to let hard boarders block free thinking.

Moving away from a world of just 0s & 1s and adding things like |0>&|1> could have all sorts of crazy impacts in 20yrs that we can't even imagine today.

I was just trying to be optimistic and get a little excited about a concept that really could change our understanding of things, and hopefully get more people to watch those videos and learn more about it. It was meant to be crazy, exciting and hopefully motivational.

Very sorry if I offended your sense of reality, I was just excited about the 20, 50, 100yr possibilities of things like "spooky action at a distance"

Re:The next major revolution will be quantum..... (1)

FrangoAssado (561740) | more than 2 years ago | (#37582634)

Between the Easter Bunny, Santa Clause and now the Speed of Light, I've learned not to let hard boarders block free thinking.

Why not throw away conservation of energy, also? Don't let reason block your creativity, quantum computing could heat your coffee for free!

Re:The next major revolution will be quantum..... (1)

Desmoden (221564) | more than 2 years ago | (#37596242)

Now you are just being silly

Re:The next major revolution will be quantum..... (1)

FrangoAssado (561740) | more than 2 years ago | (#37596504)

Yes, and my point is: it's no sillier than suggesting that quantum entanglement can be used to transmit information faster than light.

Really. In the current model of quantum entanglement, which is part of the foundations of quantum mechanics and exists more or less unchanged since (at least) the 1950s, it's very clear that information (or anything else) can't travel faster than light. Beyond that, there have been lots of experiments testing and exploring all subtleties of entanglement, since the 1970s. All the results conform in all aspects to the "standard" theory for quantum mechanics. All phenomena that we have been able to observe fit the current theories.

You could say "that doesn't mean that it's impossible, maybe some other experiments will find something someday", and that's true. But that's also true of conservation of energy, or the ontological status of the Easter Bunny (there's a phrase you don't head often :)).

There's a misconception that I've noticed in some people (I don't know if it includes you): the impression that people who think that quantum computing is an attainable goal also believe that entanglement must have some power that breaks the known laws of physics (for example, the speed of light limit). Usually, though, people with this misconception come to believe that quantum computing must be impossible (which, ironically, is the opposite of what you suggest -- that not only quantum computing is possible, but that entanglement does have the power to send information faster than light)

As far as our current understanding goes, though, none of that is true. Quantum computing is firmly founded in the current theory of quantum mechanics, respecting special relativity and all (i.e., the limit of the speed of light).

Re:The next major revolution will be quantum..... (1)

angel'o'sphere (80593) | more than 2 years ago | (#37660736)

Really. In the current model of quantum entanglement, which is part of the foundations of quantum mechanics and exists more or less unchanged since (at least) the 1950s, it's very clear that information (or anything else) can't travel faster than light. Beyond that, there have been lots of experiments testing and exploring all subtleties of entanglement, since the 1970s. All the results conform in all aspects to the "standard" theory for quantum mechanics. All phenomena that we have been able to observe fit the current theories.

This heavyly depends on your defnition of "faster than light". Because some of the entangelment restrictions belived to hold are meanwhile obsolet since the mid 90s.
E.g. if you entangle 2 particles and seperate them, both in their own storage device, it was believed you can not watch one particel and notice when the entanglement is broken by the other one. This is disproved by experiments last century.
So it is possible to ship a box with particles to mars and keep their entangeld counterparts on earth. As the particles are transported with ordinary means there is strictly speaking no faster than light communication happening. However: the guys on Mars see the breaking of the entanglement instantly when it is broken on Earth.

Re:The next major revolution will be quantum..... (1)

FrangoAssado (561740) | more than 2 years ago | (#37665568)

[...] it was believed you can not watch one particel and notice when the entanglement is broken by the other one. This is disproved by experiments last century.

Can you post (established) references, please? The only thing I heard about that is a paper from B. Dopfer in 1999 (I can't find a link right now) where they supposedly were able to stop interference by measuring entangled particles. I have seen a few critics, but mostly the lack of references from other papers is what makes me suspicious about it: surely this would be huge news, and a lot more people would be talking about it, no?

And in you scenario, nothing depends on anyone's definition of "faster than light". If you can make information from Earth (at point A) available in Mars (at point B) before light has time to travel from A to B, there's no discussion: there is faster than light communication, regardless of how you prepared the whole stuff. Claiming otherwise would be as silly as claiming that communication via radio is no faster than a train because you had to send the radio via train in the first place.

Re:The next major revolution will be quantum..... (1)

angel'o'sphere (80593) | more than 2 years ago | (#37672878)

Can you post (established) references, please?

I have read that in Scientific American, quite a few years ago.

And in you scenario, nothing depends on anyone's definition of "faster than light".

It does. As most physics accept that such watching on entanglements is/might be possible. However the general argument is: the first movement counts. Regarding "causality" at least.

However you have a funny argument ;D with your radio and train.

Re:The next major revolution will be quantum..... (1)

FrangoAssado (561740) | more than 2 years ago | (#37680398)

I have read that in Scientific American, quite a few years ago.

Well, as great as Scientific American is, can we at least agree that it publishes a lot of stories about non-established and speculative theories? I'm talking about papers by real physicists that have been peer-reviewed and referenced by other physicists.

It does. As most physics accept that such watching on entanglements is/might be possible. However the general argument is: the first movement counts. Regarding "causality" at least.

I doubt that "most physics accept" that, at least in the terms you describe. Within one of the most basic foundations of modern physics (Special Relativity), it doesn't even make sense to talk about which came first between A and B if B is outside the light cone of A (that is, if light from A can't reach B), so your argument can't even be made precise within current physics. That's not a pointless objection: in your scenario, as far as Special Relativity goes, it would be possible to have one observer concluding that Mars measured first, and another one concluding that Earth measured first.

It is possible to propose new alternative theories, of course. But it's usually best to suspend judgement until they have been made precise and published for general scrutiny. That's why I wanted references to papers; I wanted see the reactions from real physicists.

Re:The next major revolution will be quantum..... (1)

angel'o'sphere (80593) | more than 2 years ago | (#37683030)

Quantum encrypted channels work on the exact same principle and are already in general use. I don't see your point.
Also I assumed Scientific American was a respected peer reviewed physics magazine. Am I mistaken here?

Re:The next major revolution will be quantum..... (1)

FrangoAssado (561740) | more than 2 years ago | (#37683264)

Quantum encrypted channels work on the exact same principle and are already in general use. I don't see your point.

Quantum encryption, as all other established results that use entanglement (like quantum teleportation, etc.), don't presuppose or rely on entanglement being able to send information faster than light.

Also I assumed Scientific American was a respected peer reviewed physics magazine. Am I mistaken here?

Scientific American is a magazine that does science popularization, its articles are nowhere near the level of rigor necessary for a peer-reviewed physics journal.

Re:The next major revolution will be quantum..... (1)

angel'o'sphere (80593) | more than 2 years ago | (#37683746)

As I pointed out before: strictly speaking the information is not sent faster than light as the entangled particles have to be moved by "conventional" methods.

The "raw entanglement" or however you want to call it, the fact that entanglements break etc. is "transmitted" instantly.

After all this is the "god is not rolling dices" counter argument form Einstein.

If you want to argue about entanglements than this should be the most basic thing to know.

That the scientific american is not a reputated magazine is for me the first time to hear ... what magazine would you suggest then?

Re:The next major revolution will be quantum..... (1)

FrangoAssado (561740) | more than 2 years ago | (#37684330)

Sigh... I don't think we're going to make any progress.

I've explained to you that in current physics, it doesn't make any sense to talk about "instant transmission" in the sense you're talking about. I've explained that in the current model for entanglement, there's no need or place for any such "instant transmission". Yet you keep insisting on a non-standard model for entanglement where information is sent faster than light, but "it's ok because you had to send the particles beforehand" (which, I have mentioned, is not only inconsistent with current physics but seems silly).

As I said, Scientific American is a magazine that does science popularization. While sometimes some articles are written by researchers, it's mostly written by journalists. If you're looking for papers with the current research on the foundations of quantum mechanics, you should check peer-reviewed physics journals; there's a nice compilation in Wikipedia [wikipedia.org] . There's also Arxiv [arxiv.org] , but the papers there are not necessarily peer-reviewed.

Re:The next major revolution will be quantum..... (1)

angel'o'sphere (80593) | more than 2 years ago | (#37687910)

Well,
then I simply don't get your point.

Yet you keep insisting on a non-standard model for entanglement where information is sent faster than light

Do you want to claim that breaking entanglement is not instantly? Sorry, but then you are a bit out of the loop. It was never assumed that it took any time to be observed. It was assumed "it could not be observed". And this later point has changed in recent history. It was always clear that breaking entanglement has its "effect" transported instanly regardless of distance. That is not my "interpretration" but what is tought in school since ever.

Regarding your strange attempt to citate me: 'but "it's ok because you had to send the particles beforehand"' ... I did not say that. Sigh. How hard is it to read? I said: some phyics say this! And the "it is ok" is not making the point.

The question is: is it truely observeable "on the other side" or is it only observeable as a mass effect? And how does it fit into the rest of physics? I said, there where mentionings in news a few years ago that you can observe it (on particular particle) ... thats all I know ... I don't know if it is "confirmed" but I assumed that quantum secured communication where wiretapping can be detected as certain properties of entangeld photons change supports this.

Thanx for the links though.

Re:The next major revolution will be quantum..... (1)

FrangoAssado (561740) | more than 2 years ago | (#37696302)

Do you want to claim that breaking entanglement is not instantly? Sorry, but then you are a bit out of the loop. It was never assumed that it took any time to be observed. It was assumed "it could not be observed". And this later point has changed in recent history. It was always clear that breaking entanglement has its "effect" transported instanly regardless of distance. That is not my "interpretration" but what is tought in school since ever.

"Breaking the entanglement is instantaneous" is a question that, currently, nobody knows the answer, but that's because this question is about the interpretation of quantum mechanics [wikipedia.org] , and can't be settled, as far as we know, with experiments. What people do believe, though, is that even if breaking the entanglement is "instantaneous" (I write it in quotes because that can't even be made precise with current physics, as I've explained), no information can be sent "instantaneously". I'm curious to see this article on Scientific American that gave you the impression that this is not so.

Some interpretations of quantum mechanics try to explain things in terms of faster than light effects ( that 's what Einstein derisively called "spooky action"), but these are just interpretations of the math and the outcomes of the experiments. There's no consensus of whether it actually happens or not. And, more importantly, not even people who use these interpretations think that these "effects" can be used to send information faster than light. It should be clear how this works once you understand the math and experiments.

I've resisted doing this so far, because I didn't want to sound disrespectful, but it seems that you have a wrong impression about entanglement. Do you know how the mathematics of entanglement works, or just things you read in science popularization articles? There's an excellent series of introductory lectures from Stanford University in Youtube that teaches the basics of quantum entanglements starting here [youtube.com] . The lecturer is a very famous physicist, Leonard Susskind. If you watch the whole thing (and follow the math explanations carefully), you'll notice that he never talks about "instantaneous" anything, and it's there's no reason to do so. And the math isn't too hard to follow, you only need to know basic algebra, complex numbers and matrices.

Regarding your strange attempt to citate me: 'but "it's ok because you had to send the particles beforehand"' ... I did not say that. Sigh. How hard is it to read? I said: some phyics say this! And the "it is ok" is not making the point.

Sorry, I misunderstood you. I had never seen it before, and I thought you believed this.

I don't know if it is "confirmed" but I assumed that quantum secured communication where wiretapping can be detected as certain properties of entangeld photons change supports this.

I't true that it's possible to detect eavesdropping in quantum secure channels, but that's due to the uncertainty principle and the no cloning theorem [wikipedia.org] , not entanglement. It's almost impossible to really understand these intricate things, though, without understanding the underlying math.

Re:The next major revolution will be quantum..... (1)

Interoperable (1651953) | more than 2 years ago | (#37580866)

I think that if a robust quantum computer were developed, specific algorithms would follow. Quantum computing allows you to exploit a larger computational basis than classical computing for a given number of (q)bits. The extra internal degrees freedom in a quantum state, thanks to entanglement between the elements, mean that the state-space is much larger than for a classical system and the promise of using that as a computational basis is hard to ignore.

Re:The next major revolution will be quantum..... (1)

AP31R0N (723649) | more than 2 years ago | (#37583062)

Does Grover's algorithm determine is something is NEAR or FAR?

Stupid filter....

Re:The next major revolution will be quantum..... (1)

narcc (412956) | more than 2 years ago | (#37579486)

I've had a Quantum Fireball hard drive for years.

I can't use it anymore though. Every time I've tried to read from it, my cat dies.

Re:The next major revolution will be quantum..... (3, Funny)

JoshuaZ (1134087) | more than 2 years ago | (#37579494)

I can't use it anymore though. Every time I've tried to read from it, my cat dies.

Something must be wrong with your drive. Your cat should only die half the time.

Re:The next major revolution will be quantum..... (3, Funny)

maxwell demon (590494) | more than 2 years ago | (#37579604)

I can't use it anymore though. Every time I've tried to read from it, my cat dies.

Something must be wrong with your drive. Your cat should only die half the time.

Actually, on average only every 18th time the cat should die. Yes, half the time the cat will lose its life. However, everyone knows that cats have nine lives.

Re:The next major revolution will be quantum..... (1)

martin-boundary (547041) | more than 2 years ago | (#37581480)

Except in Australia. In Australia, cats have 6 lives, so death only occurs 1/12th of the time.

Re:The next major revolution will be quantum..... (0)

Anonymous Coward | more than 2 years ago | (#37586668)

Those are kangaroos, mate.

Re:The next major revolution will be quantum..... (1)

atisss (1661313) | more than 2 years ago | (#37588336)

No, cat dies every other time, but you need a new cat every 18 attempts.

Re:The next major revolution will be quantum..... (3, Insightful)

maxwell demon (590494) | more than 2 years ago | (#37579534)

Quantum, or more specifically quantum mechanics will be the next Major human revolution.

Actually quantum mechanics already is the previous revolution. Lasers are quantum. Semiconductors are quantum. Without quantum mechanics, our computers would still be big monsters of tubes with the power of a pocket calculator. The giant magnetoresistance, which is the base of our high-density hard disks, is a quantum effect. Without quantum mechanics, the whole information technology revolution could not have taken place.

That's not to say that quantum information wouldn't be a huge step from that. It's applying quantum mechanics to the information itself, instead of "only" using it to improve the handling of classical information. However, reducing the impact of quantum mechanics to quantum information vastly underestimates its importance. Even if the quantum computer should turn out to be impossible for some reason, quantum mechanics will not become useless. Almost all of our modern technology is based on it.

Skip at least first 4 or 5 videos (0)

Anonymous Coward | more than 2 years ago | (#37579374)

It annoys me when people say they are going to assume you have a knowledge of something (in this case linear algebra) and then spend half the course recovering the very basics of exactly that assumed knowledge. Even more annoying is when the notation that is new is mixed in so that you have to sit through linear algebra 101 just to get familiar with the notation and relevant language.

Re:Skip at least first 4 or 5 videos (0)

Anonymous Coward | more than 2 years ago | (#37579720)

His proof that unitary matrices are length preserving in lecture 6 is a bear to follow in scribble mode. I guess I'll have to look that one up.

Re:Skip at least first 4 or 5 videos (2)

2.7182 (819680) | more than 2 years ago | (#37580702)

It's idiotic to prove that. The right way to do things is define them as inner product preserving and then it's immediate that they are length preserving.

Re:Skip at least first 4 or 5 videos (1)

FrangoAssado (561740) | more than 2 years ago | (#37581316)

It's idiotic to prove that. The right way to do things is define them as inner product preserving and then it's immediate that they are length preserving.

... what?

That's like saying "It's idiotic to prove the Pythagoras theorem. The right way to do things is to define 'right-angled triangle' as a triangle that has sides obeying a^2=b^2+c^2". Sure, you could do that, but then you have to prove that a triangle is 'right-angled' iff it has one of its angles equal to 90 degrees.

Similarly, if you define "unitary" as "inner product preserving", then you have to prove that U is unitary iff UU*=U*U.

Re:Skip at least first 4 or 5 videos (1)

2.7182 (819680) | more than 2 years ago | (#37583058)

Right. Which is the correct logical order, since unitary transformations are isometries. Then the property you mention follows easily.

Re:Skip at least first 4 or 5 videos (1)

FrangoAssado (561740) | more than 2 years ago | (#37584570)

Then the property you mention follows easily.

No, you can't do that. There's a difference between "iff" ("if and only if") and "if"; you don't just have to prove

"inner product preserving" => UU*=U*U=I

What you need is

"inner product preserving" <=> UU*=U*U=I

If you do that, it doesn't matter what you use as definition and what you prove, the work is exactly the same. So you might as well use the same definition as everyone else.

Re:Skip at least first 4 or 5 videos (1)

2.7182 (819680) | more than 2 years ago | (#37586570)

OK, sure, you certainly do want that. From a geometer's point of view though, one of course always defines things first with the inner product. Either direction is fine, but they are both exceeding easy to show. I shot from the hip, I admit. The idiotic statement was really reacting to this latter point that this isn't hard to show. It call me back to classical mechanics texts/courses where there is a huge amount of effort put in to showing that an element of O(3) has an eigenvector, when it is a 3 line observation. (Try looking it up in Goldstein for example, and compare with Artin.)

Re:Skip at least first 4 or 5 videos (1)

Anonymous Coward | more than 2 years ago | (#37582152)

After watching the first 4 og 5 videos, I was amazed as I realized I was able to think about some things as he explained about qubit computation. Perhaps for the first time I got an idea what a "complex conjugate" could be and a vague idea for how it might be interesting. He did not explain this though, but I have been following some videos on quantum mechanics. Perhaps I will come to realize later on, that I have misunderstood something I thought made sense, but right now it made math more interesting.

Observer effect (0)

Anonymous Coward | more than 2 years ago | (#37581026)

Due to other work responsibilities, he stopped short of completing the course, and will only complete it if he sees enough interest in the videos. Let's show him some numbers.

So in other words, if no one is looking at his videos, they won't exist?

Best intro to quantum computing I've seen (1)

DeathCarrot (1133225) | more than 2 years ago | (#37584244)

I've read a few articles on quantum computing before this, and while they tend to give a general idea of what it's about, they tend not to go into any depth on quantum logic and what you can actually do with individual qubits (or if they do, they're so dry I end up falling asleep before that point). These videos show what kinds of operations you can perform on qubits mathematically and how you can form concrete quantum circuits/algorithms out of quantum gates. The bits on superdense encoding and quantum teleportation certainly helped put everything into perspective. They're aimed more at the computer scientist or mathematician rather than the physicist, which suits me just fine. My only critiques would be that he goes into (imho, superficial) proofs too often, he could have drawn more parallels with boolean logic and illustrated a lot of the linear algebra with visual representations.
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