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