10:00 PM
::makes fresh popcorn::
Zzzz...falls asleep waiting

@DanielSank Let's see now. Hmmn. I don't think Josephson junctions or electronics or engineering or superconduction or weak measurement is bunk. And I didn't actually use the word bunk anyway. But since the overall subject is quantum computing, perhaps I might politely point out that it's been ongoing now for over four decades with no discernible benefit, and qubits counts are minimal as is stability. Sorry.

@0celo7 Your default mode is clueless about various elementary problems.
2

Did you know that, until recently, starring was not exactly anonymous?
69

So I was making a chatbot in Ruby for SE chat, and I discovered that I could find out the starrer of a message. I'm pretty sure stars, like votes, are supposed to be anonymous. Although this knowledge would help for cases of star trolls like this. Here's the specific slice of code that do...

@DanielSank What did you say about me?!

10:15 PM
@Danu wow
That hurt!

Don't hurt my pal, you bully :P

@0celo7 Don't worry, it was just the best trash talk I could come up with in a moment's notice. Also, I didn't see until later that you weren't actually talking about me, and @ChrisWhite is actually the one who deserves to get counter-trolled...

@Danu no, that actually hurt
I really am shit at easy problems
@ACuriousMind This video contains content from SME, who has blocked it in your country on copyright grounds.
huh!?!?

lol, that one isn't blocked in Germany :D

10:18 PM
Sigh... It's fine dude, you're just starting out at university. You're not expected to be like... solving problems that me and others who are supposed to be years ahead of you don't understand just yet

I'm confused
how do I chat code thing?

I think they fixed it

:23819034 I now believe that you can't program :P
Also, note my "until recently"

@Danu I can't solve first year problems according to ACM

@JohnDuffield Could you please tell me what you think I'm asserting?

10:20 PM
@ACuriousMind ah, I read that as "starring was anonymous until recently"

@JohnDuffield Why are you sorry?

@Danu well why did you say "elementary" then

If you are reading Hawking and Ellis at 17
You're probably fine
I mean

user54412
10:21 PM
@0celo7 I think you're just proportionally less interested in easy problems, so you don't spend as much working on them.

Life will still crush your dreams
3
But that is for later

dude that freaking "how to write your resume" talk crushed my dreams

The tip is "lie a lot"

You have to view things in a more laid-back perspective

user54412
@Danu bring it :p

10:22 PM
For instance, I didn't know what "topology" meant until about 13 months ago.

Hey, @JohnDuffield, how come you think weak measurement is a worthy pursuit? What benefit, to use your own word, has that lent us?

(as in, I'd actually never seen the definition)

Topology is the science of places
Like

@DanielSank before I embark on the journey into quantum computing textbooks, are there any QM things that I should review?

Paris or London
Go there
That is topology

10:23 PM
I think my father things topology = topography

user54412
^^ ?

Anyone here use google+?

@0celo7 For the basics, as long as you can exponentiate a pauli matrix you're probably fine.

I do, but only to keep tabs on a dude I despise

@DanielSank I can!

10:24 PM
(I only live for revenge)
3

@0celo7 Fairly-land quantum computing requires basically zero advanced quantum mechanics.
It's only when you get into real life decoherence issues that things become interesting/hard.

so like no scattering theory or tensor operators?

I never really sunk much time into tensor operators

@Slereah You are a weird, weird man. I like you.

10:25 PM
From what I can see quantum computing is mostly like

@ChrisWhite You aren't invested enough in the opinion of the people in this chat ;)

Apply operators on states at quantum gates
You also have mixed states
And then you collapse that shit for the result

@0celo7 It depends on what level you're at. If you're just studying quantum computing in the abstract information processing sense, then there's really very little physics. If you get into physical implementations then you need to know whatever physics is relevant to that implementation.

user54412
@Danu Well that's too bad. I had a mango tree all ready to go, too.
2

10:26 PM
@ChrisWhite Is that a reference to my link from the other day?

@DanielSank I'm going to skim a 157 page "book" on it during my free time this week and over the weekend to see if I'm interested in a more thorough study

user54412
@DanielSank Of course it is. You've shared great wisdom with us all.

@DanielSank I get to do one of those stupid reading quizzes again!
"vector kinematics"

@ChrisWhite I'll ram it in!

That's...not a very creative comeback.

10:29 PM
^

@0celo7 I have a better idea.

@ChrisWhite Perhaps, but I don't think I could ever come up with the tricks to do the problems in Carothers.

@0celo7 So, just for reference. I went through a whole book "How To Prove It" by Velleman before I touched Rudin

Go work out the Hamiltonian of an LC oscillator.

LC?

10:30 PM
but when I got to Rudin I found it tackleable. Really hard and time consuming, but I finished every problem in the first four chapters (and then decided I was spending way too much time on it)

@0celo7 Parallel inductor/capacitor.

the heck is that

ew electronics

@NeuroFuzzy hmm

@ACuriousMind Sometime I gotta set our resident "dry German" up for some good comments too ;)

user54412
10:31 PM
@0celo7 A friend of mine (one of those wins-every-math-competition-ever types) once said there's only about 3000 different math competition problems, and once you've seen the trick for each one, you know how to solve them all. My own corollary is that there's only a couple tricks for each subject, and once you know them you can solve all the problems.

user54412
Real analysis is all one trick -- give yourself an epsilon budget, and make all your deltas small enough to not exceed it. Once you've struggled with a few dozen of these problems, the rest become much easier.

@0celo7 Go learn enough basic electronics to understand the classical equations of motion of a parallel LC oscillator. It should take you 20 minutes. Then figure out the quantum Hamiltonian.

@ChrisWhite I hope you're kidding :P

Tell me when you're done and I'll give you another problem. A couple of months from now you'll know what a CZ gate is, how it works in real hardware, and why it's hard.

I think it's rather obvious that there are many hundreds of tricks in most fields :P

10:34 PM
@0celo7 and you'll be able to help me convince @JohnDuffield that's his perspective on quantum computing may be unnecessarily pessimistic.

user54412
@Danu Replace "field" with "1 semester's worth of material"

When I was 17 I was just trying to solve problems on Hyperphysics
That site is old as hell

@DanielSank I don't even know ohm's law

@0celo7 actually, if you want I can email you my page of "all the quantum tricks I ever need for my work" and you can try to prove them all.
@0celo7 Look it up.

@ChrisWhite ...ah :P I guess I agree ;)

10:36 PM
It's really simple. Suppose you have a particle with a lot of friction, characterized by a friction coefficient $\mu$. You push on it with force $F$. What happens?

Define "trick"

When I was 17 I was just trying to not do my homework and play video games, have sex with my girlfriend and generally chill out
I don't regret it :P

@Danu And what's different now?

@DanielSank there's a resistance

Hm, what year was 17
2003
What was I doing back then

10:37 PM
damn you're old!

@Danu I'm supposed to be the Californian here and I feel like you're trying to steal my spotlight :(

@DanielSank I spend >75% of my free time on mathematics/physics now.

Picture this scene in your mind's eye
Imagine my grave

lol

Upon which stands the Grim Reaper

user54412
10:38 PM
Are the Dutch the Californians of Europe?

He slowly turns to you

I shoot him

And points at you with his bony fingers
And whispers

by the time you're dead I'm old enough to carry

ONE DAY, YOU

10:38 PM
@0celo7 Yeah. Describe the motion of the particle.

@ChrisWhite With the opposite type of weather...

@DanielSank $ma=F-\mu mg$ IIRC

@0celo7 Carrying guns is for weaklings ;) Just strangle him

he has no trachea
nor veins

but he can be shot

10:39 PM
for he is a skelinton

@Slereah Imagine this, you stand in front of a table on 0celo7's grave, across from Death. He's visibly frustrated, shakes his fist nearly knocking the scrabble board to the ground, and says

uh, what is bullet hit bone = broken bone

You can just break his neck with your bare hands then, I figure

ONE DAY, U

@NeuroFuzzy Hehehehe

10:40 PM
Danu is like Rambo

@0celo7 Just say the friction force is $F_\text{friction} = - \mu \dot{x}$.

@DanielSank TIL...

@Slereah That does not look like a link I want to click

@0celo7 Well, what you wrote is correct for friction between an object and a surface, where the friction comes from the normal force due to the object's weight.

10:41 PM
@NeuroFuzzy I think you're asserting a misguided version of SR that permits time travel. It doesn't.

@Slereah hahahah
lol

I'm thinking more of, say, electrons moving in a conductor...

@DanielSank Yes, I know that

Seems like @JohnDuffield panned my entire field and left. Poor form.

Call me stupid, I have no clue where your equation comes from

10:42 PM
@ACuriousMind is it
2 spooky 4 u

@0celo7 The $- \mu \dot{x}$ thing?

Is it postulated or derived?
@DanielSank yeah

It's a friction term

I didn't see that in AP physics

So postulated, yeah

10:42 PM
@0celo7 Can be derived if you imagine your object moving in the presence of other things it can crash into.

Usually friction terms are ~v or v²

ohhhhhh, I do know that!
ok

The faster you move, the more things you crash into per unit time, so the more impulse you get from them per unit time.
Ok, @0celo7, so what happens to the motion of the particle?

Um, I'm assuming it hits some max velocity

10:44 PM
@0celo7 Yup. What is that max?

if $F$ is constant, this is just like drag on a falling object

Yup.
Max velocity is?

@DanielSank $F/\mu$ I think

you are on 4chin too much

10:45 PM
@Slereah wat

@ACuriousMind 4chan thing

I just love skeletons :(

@JohnDuffield I'm not asserting SR permits time travel, nor that the suppostions made in my post are correct or physical.

@Slereah thank mr skeltal

@0celo7 Yes.

10:47 PM
@DanielSank I'm sorry because you're working in a field where it's difficult to demonstrate progress. I think weak measurement is important because it will lead to the replacement of the Copenhagen interpretation. See Jeff Lundeen et al.

quantum interpretation time
@ACuriousMind please explain which is best and why

@JohnDuffield Difficult to demonstrate progress? How many orders of magnitude do you think superconducting qubit coherence times have increased in the last ten years?

@DanielSank ok, I learned all of this in high school, what next?

49 mins ago, by Rigor
::makes fresh popcorn::

@0celo7 Now apply this reasoning to an electron in a material in which it has some rate of crashing into scattering centers.
Say the force is $F = q E$ where $E$, the electric field, is associated with a voltage difference on the ends of the wire: $E = V / d$ where $d$ is the wire length.
You'll be at Ohm's law in no time.
@JohnDuffield Do you actually pay attention to experimental quantum computing literature or are you shooting from the hip here?

10:51 PM
@DanielSank Did Einstein publish on quantum computing? ;)

Are you aware, for example, that we can measure a superconducting qubit's state in less than 200ns with more than 99% accuracy? Did you know that we can do 2-qubit gates with almost 3 nines accuracy?
@Danu I have no idea. Probably not. Why?

@DanielSank You're not getting the reference.

@DanielSank so $I=q/t$, right?

Clearly, you spend too little time in this chat

Duffield only trusts EINSTEIN

10:52 PM
AND THE EVIDENCE

user54412
@Danu Some people don't read the entire transcript

@ChrisWhite Despicable peasants

@NeuroFuzzy You said "If you allow instantaneous communication to occur in just two distinct reference frames, then you do violate causality." You don't. I now that's what people say, but it just isn't true.
@DanielSank I pay attention. I'm not shooting from the hip. @Slereah : I trust the evidence more.

@JohnDuffield Okay, so why is the Earth-Alien-Outpost paradox I gave incorrect?

He does.

10:54 PM
@ACuriousMind throw some popcorn across the lake

Our very own Sherlock Holmes

@Danu Also known as "people with a life"

@ACuriousMind are those groups mutually exclusive?

@ACuriousMind That.

@0celo7 What groups?

10:55 PM
@0celo7 Yes.

@DanielSank what is $\mu$ in the electron case?

@ACuriousMind ...soon to be ended!

@NeuroFuzzy because you mistake the changes that happen to you when you change your speed for changes that happen to the other things. Nothing happens to those other things, or to the signals moving from one thing to the other. Nothing at all.

Anyways, time to sleep
bye guys

@0celo7 Leave it as a parameter and see what happens.

10:56 PM
@Danu night
@DanielSank I just get $$v_\text{max}=\frac{qV}{d\mu}$$
what is the speed of an electron?

@JohnDuffield I don't see how that's the case. I interpret "Allow instantaneous communication in a frame" to very precisely be, like in my electrodynamics example, something like $\div \cdot E=\rho(\mathrm{Earth},t)+\rho(\mathrm{Andromeda},t)$, where the positions and times are defined absolutely in this privileged frame of reference.
How else can one interpret that?

@DanielSank Yes, difficult to demonstrate progress. How long does the coherence last, and how many bits do we have? Compare and contrast that with the £50 terabyte disk drive on my desk.

@0celo7 You know how fast the electrons are moving, right? Current is by definition the amount of charge moving past some point per time.
So, if the wire has electron number density $\rho$ then the current is $I = v \rho q$.
@JohnDuffield Coherence levels are already sub-threshold for surface code error correction.
@JohnDuffield Comparing a cutting edge research technology to hard drive is such an obvious trip to logic hell that I respectfully decline the invitation.
@JohnDuffield I invite you to apply the same reasoning to the construction of CERN.

So $$\frac{I}{\rho q}=\frac{qV}{d\mu}\implies I=V\frac{\rho q^2}{d\mu}$$ so somehow $$\frac{\rho q^2}{d\mu}$$ is $1/R$?

@NeuroFuzzy : your frame is just "a state of motion". The instantaneous or very fast communication has got nothing to do with whether you're moving. Positions and times depend on those other things and the motion of light through the universe or CMB frame that serves as your de-facto absolute frame, not on your motion.

11:07 PM
@JohnDuffield Well it does have to do with whether you're moving, because there's no notion of instantaneous if you don't choose a frame. How do you define "instantaneous" independent of a frame?

You just define it as it happens real quick. You don't need a frame to define that. Perhaps you're thinking of simultaneous?

@0celo7 That looks about right!
Good job, you just derived Ohm's law in the so-called Drude model!

@DanielSank well I don't see how that's resistance
and I have to go now, ANS meeting
will be back, but have psychology homework

@JohnDuffield instantaneous communication over a finite distance

@DanielSank I'm not a big fan of CERN as it happens. There's a bit of a gap between the physics and the publicity. One for another day I'm afraid.

11:11 PM
@JohnDuffield you need a notion of simultaneity or something for instantaneous communication over a finite distance.

@JohnDuffield Is your criterion for useful research that it must produce useful technology within some specific span of time, starting from some threshold at which a certain amount of money is spent on that field?
@JohnDuffield also, nothing you've said so far explains why you referred to quantum computing as "pseudoscience". Can you explain that?

@NeuroFuzzy So quick it's like it's instant. It's no big deal. You don't need a notion of simultaneity. You just talk to the guy on the "subspace radio". Now. You say something, he says something. Pretty instantly. And when you accelerate towards him, nothing special happens.

@DanielSank as for your Hamiltonian, I probably need to know the frequency of oscillation

@JohnDuffield You can't possibly believe that's what the OP's question was about... instant as in a million years instant (andromeda).

Then somehow find the conjugate variables

11:15 PM
@0celo7 Oops, we forgot a factor of the area of the wire. The current is $I = \rho v q A$ where $A$ is the cross-section area of the wire.
Put that in and you've got the right answer!

@DanielSank : no, my criterion for useful research is not that it must produce useful technology within some specific span of time. My criterion is that it helps us to understand the world. That's why we do physics. We don't do it to come up with £50 disk drives. The problem is that the Copenhagen interpretation is the antithesis of understanding, and quantum computing is related to it.

@DanielSank my interest and knowledge in "simple" electronics is null

@JohnDuffield Listen to me very closely: I am a quantum computing professional and I think the Copenhagen interpretation is not even self-consistent and therefore entirely inadmissible as a theory of Nature.
@0celo7 That's ok.
You just derived Ohm's law. I'd say you're doing well for your first day.

@NeuroFuzzy you fool
Don't engage
@DanielSank : What is your fave interpretation

Mud wrestling with a pig is awesome because in the end you can get bacon
4

11:18 PM
@Slereah I call it the Sank interpretation.
@JohnDuffield Also, why does the favorite interpretation of quantum computing practitioners have anything to do with whether or not the idea will work?

@NeuroFuzzy : the OP's question is clear enough. The nonsense creeps in with the Andromeda paradox. It's popscience woo. Changing your motion doesn't change something on some distant planet.

@DanielSank Another QM interpretation!
I guess the 30 others weren't good enough :p

@Slereah Nope.

quantum computing is so basic QM that I don't think quantum interpretions have anything to do with it

I can hear @ACuriousMind cringing at all this mentioning of interpretations

11:21 PM
@0celo7 Do you know what impedance is? If not, I strongly recommend learning about it, as it will make a lot of things that QFT practitioners make out to be really complicated seem extremely simple.

impedance is a fancy word for resistance :p
Except complex

@Slereah No, it's not.
It's a fancy word for "linear response coefficient".
@0celo7 If you doubt my previous statement, read this post.

Exactly

@Slereah Ok ok, fine :P

I have no clue what it is

11:23 PM
@DanielSank Or perhaps "linear response coefficient" is a fancy word for "impedance"?

What's the use of impedance in QFT?

@JohnDuffield So, are you saying that my mistake is in not stopping at the OP's sentence "Lets assume - against all possibility - we find a strange device fixed earth an on alpha centauri and we could communicate nearly instantly with alpha centauri through this device in both direction. Nobody knows why and how, but it just works." and saying "nope, nuh uh, impossible, never been observed, nonsense, woo, do real physics"?

Is it used for like
Propagation of quantum fields
or we

@Slereah It helps understand things like "pole prescriptions".
Not impedance per se, really just linear response theory. However, understanding impedance is really nice because when doing circuit analysis you come across things like poles moving off the real axis for physical reasons.

I really liked that post (although I never found "shifting the contour" all too mysterious)

11:26 PM
Birrell has a section on pole prescriptions
There's like seven fucking different ones

Then you can easily understand wtf is going on when QFT books do it will-ye nill-ye.
I gtg for now, guys.
ciao

Going round one pole, going round the other, going round both, going round both doing a loopdeeloop
Going above them, going beneath them and going in between them
so many fucking contours

@DanielSank nooo how do I into LC Hamiltonian

@0celo7 oh, energy of capacitor ("potential") + energy of an inductor ("kinetic")

@DanielSank : I'm pleased you think the Copenhagen interpretation is inadmissible. You might want to take a look at this and have a little think about the speed of light and c = √(1/ε₀μ₀) and Z₀ = √(μ₀/ε₀). Meanwhile, it's late here in the UK. Time for bed.

11:32 PM
@0celo7 so capacitor energy is proportional to the charge difference between the cap plates squared

@NeuroFuzzy how do I into capacitor and inductor
What on earth are these words
Can I go back to differential geometry

@NeuroFuzzy Yeah, pretty much. There's an awful lot of woo out there. More than you think. And the thing is this: everybody who believes in woo clings to it like a teat. They will dismiss Einstein and the patent blatent evidence to cling to it. But anyway, like I said, time for bed.

@0celo7 Eep, okay, so, first bit of advice: for a lot of this stuff the people who pass the tests on it/get good grades can get by without really understanding it.
@0celo7 so, like, you can use heuristics to get the formula for energy stored in a capacitor
@0celo7 or you could go from Maxwell's equations to it

I'm doing electronics next year

@0celo7 but even then you're still looking up Maxwell's eqs with boundary conditions in the back of the book. So basically use a mix of deeper understanding and superficial understanding :D
@JohnDuffield Well please for the sake of both of our time, just say that next time! We've wasted time arguing about absolutely nothing. I could say "I think it's instructive to fiddle with SR and see why exactly it precludes that" and then we'd actually be arguing about something of substance. But we haven't argued about anything of substance yet even though we could fill up a few pages with what we've written! Sheesh.

11:43 PM
Please do not argue with John
It does not work

@Slereah but it's just so frustrating :(

I know
So apparently quantum gravity in 2D is basically solvable?
Which doesn't mean much really since it's just a lambda term
But still quite neat
though I think the Hilbert action somewhat enters it if you allow a sum over topology
also time to make some sammiches for tomorrow

@NeuroFuzzy what on earth are the canonical variables supposed to be

@0celo7 $Q$. just $Q$.
erm, well...
hm.

I don't know how to quantize an oscillator with one operator

11:53 PM
You're gonna need the momentum
Which is gonna be like
Time derivative of Q
or some shit

Dude this sucks
I don't know what I'm doing with that

@0celo7 Oh, I just reread DanielSank's original post.
erm message
he says work out the EOMs then the hamiltonian, which makes sense.

The EOM is just $\ddot{Q} + \dot{Q} + Q = 0$
With some factors thrown in
R's and C's and L's

I have no clue what any of this is

@0celo7 so to do that, you trace around the circuit consisting of a capacitor (two parallel metal plates in a vacuum) and an inductor (loop of wire/induces a strong magnetic field in its center) and add up voltages across them.

11:57 PM
The Lagrangian for something like that would be like...

GR is more accessible

$A\dot{Q}^2 + B Q^2 + C Q \dot{Q}$?
Something like that