The h Bar - 2017-09-02 (page 1 of 2)

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1:00 AM

Hi, everybody.

1:39 AM

Hello.

1:51 AM

Hey guys, was wondering if anyone know a mathematical model to model spectural power distribution curves? I know if it's a black body there'd be plank's equations, but what if it's not?

7 hours later…

Anonymous

9:10 AM

14

A: How antenna radiates(how currents flows through wire)

I'm guessing you don't understand how current can flow if there is no complete circuit. Let's take a simple quarter-wave dipole as an example: simulate this circuit – Schematic created using CircuitLab How can any current flow, since there is no complete circuit from "-" to "+" of V1? Co...

Anonymous

"It's true that current can't flow, but it doesn't know that until it gets to the end of the wire."

Anonymous

What nonsense....

I think that's a bit unfair. The answer is saying the aerial has a non-zero capacitance so you can push electrons along it when you apply a potential even though the circuit is not closed.

Anonymous

@JohnRennie Sure. That part of the answer is fine. I can't agree with the part that the current doesn't know. It doesn't need to, in the first place. We are applying a potential and hence charge will flow !

Anonymous

I don't understand what he meant by the word know

9:19 AM

Well he's trying to explain it in simple terms and that necessarily misrepresents the reality to some extent. I run into this all the time when trying to explain GR (and I sometimes get downvoted for it).

Anonymous

I understand :). But such statements tend to confuse people. I once spoke to a guy who thought that in a circuit current can flow to a node, turn back and return to the battery, in case there is some obstruction (like a reverse biased diode). Phew. I started to explain that that is not possible but.....Once people acquire pseudo-interpretation of reality it gets real difficult to unlearn and relearn.

Mithrandir24601

@Blue I kind of get the feeling that trying to explain current in pretty much any wordy way is a bit of a rabbit hole...

Anonymous

That's why I prefer experimental demonstration of these things as much as possible. Also, good diagrams and illustrative videos help a lot.

Anonymous

Bookish knowledge doesn't help much. :P

Mithrandir24601

9:36 AM

@Blue once you've learned certain parts of (even classical) theoretical physics, there are really good ways to explain current though:)

Anonymous

@BalarkaSen Good that you're here. I'm coming at around 4 after having my lunch. :)

k

10:26 AM

@NeuroFuzzy Thanks a lot ! You channel (YouTube) is good, but the website and khanacademy projects are brilliant! BTW, which languages you used for (a) youtube.com/watch?v=bnINsb0we7g (b) mathandcode.com/riemannian (c) mathandcode.com/block ?

11:14 AM

@rob BTW, Does getting pos attribute of a curve in Vpython works for you ? It works fine for sphere or box, but in my pc it's showing no pos attribute of curve.

2 hours later…

1:44 PM

hello

1:59 PM

@heather hi whats new, hows your new classes eg engr? :)

@NeuroFuzzy thx for dropping by, how about a speaker session sometime? clearly theres an audience eg @AlexK for 1 & me for 2 :) physics.meta.stackexchange.com/questions/7783/…

@vzn they're good =)

engineering/science are particularly great.

@heather cool what are you learning in them

and there's some good extracurriculars i'm doing (robotics, quiz bowl)

@vzn in engineering we're doing concept sketches

and in science we just finished up a quick unit on measurement. we're supposed to get into chemistry and physics so i'm excited.

@heather nice, whats happening in robotics?

@vzn it just started, so an informational meeting =P but it's the FTC program.

2:04 PM

← got into lego robotics/ mindstorms in 1999... did you hear about drone racing? recently/ now on CNN! o_O vzn1.wordpress.com/category/robotics

@heather first tech challenge, great stuff, dean kamen is a living wiz :) firstinspires.org/robotics/ftc

yeah, i'm pretty excited for it.

are you guys using a kit? cant remember if they have std kits... am guessing lots of boys in your robotics class? :)

Wow, robotics is fun.

Hi @Blue

@SwapnilDas :) yeah! what are you doing with it?

No, not me. I'm theory inclined :P

I still find stuff cool, though.

Anonymous

2:13 PM

@SwapnilDas I find it a bit boring except the theoritical stuff like AI, Machine learning.

Anonymous

But well :P

Anonymous

Some people do like it a lot

@SwapnilDas lol ok. are you in high school

Yup.

@vzn Yes, grade 11.

Anonymous

@SwapnilDas How's it going?

2:14 PM

@Blue Fine.

@Blue machine learning rocks! =D vzn1.wordpress.com/category/ai

@Blue How's life?

Anonymous

The Science club at my uni is actually a Robotics club in disguise. lol

@Blue hows the QM dabbling going

Anonymous

@SwapnilDas Good so far :) Learning lot of new stuff

2:15 PM

@vzn no kit, and yeah, there's only 6-ish girls across 8th and 9th grade

@Blue do they use any particular kit(s)?

@Blue great

@heather lol "6ish", out of how many?

Anonymous

@vzn I am focusing more on learning the math now (esp Linear Algebra). Going a bit slow with QM as of now.

Anonymous

I hope to pick up pace soon

2:16 PM

@Blue good to get a good foundation :)

I'm doing Chemical bonding and COM lol.

Would anyone know if this paper: theory.fi.infn.it/becattini/files/weinberg1.pdf has been generalized to irreps of SU(3) or, even better, irreps of SU(n)? Basically I'm searching for a paper that would have a title like "Feynman rules for any SU(3) irrep" or "... any SU(n) irrep".

@SwapnilDas what is COM?

@vzn don't know exact number; let's go with ~30 or more. I say ish because others might join still.

centre of mass

2:18 PM

i'm trying to persuade some of my friends not already in it.

Anonymous

@vzn Yeah, Adruino and stuff. They do make remote controlled robots and drones too.

@ZeroTheHero sounds like a reasonable main site question to me :)

@Blue have you checked out 3Blue1Brown's linear algebra videos?

@vzn it's not really a physics question... I suppose under resource recommendation...

@Blue cool yeah thats one of the biggest these days. yrs ago it was STAMP some. had one of those, dinked around with it for awhile on physics experiment... :)

Anonymous

2:19 PM

@heather This? (youtube.com/playlist?list=PLZHQObOWTQDPD3MizzM2xVFitgF8hE_ab) I did notice it while search on Youtube but it doesn't seem very rigorous

@ZeroTheHero ofc its a Physics question. but always votes are unpredictable

@ZeroTheHero I'm not entirely sure I follow - how would an SU(n) representation affect the Feynman rules in the first place beyond attaching the corresponding group labels at the end of the lines

@Blue, yep that. it's meant to give a good intuitive foundation for the subject, and it's really an amazing series.

i cannot recommend it highly enough.

The main reason one needs "Feynman rules for any spin" is that the propagator changes with spin - but it doesn't for other representations

Anonymous

@heather Thanks. If I get time I'll go through it

2:21 PM

cool.

@Blue suggest you learn wave mechanics also incl for classical mechanics & how it ties in with linear algebra (trying to do that myself lately) :|

would anyone be willing to help me with my understanding of the answer to this question of mine?

i think i might need to reask the question adding some details i didn't think about.

@heather The answerer is in this chat right now ;)

::facepalms::

@ACuriousMind This is more or less what I thought but Feynman rules are not what Tiggers to best... Thanks.

2:23 PM

@heather answer looks good (synchronicity!)... try to study it, & you can comment on it...

@ZeroTheHero could I talk with you about your answer to my question a while back?

sure.

I need to take a 10 minute break... watch for me to come back in 10.

okay

@ZeroTheHero plz consider this sometime its on roll & next slot open :) physics.meta.stackexchange.com/questions/7783/…

Anonymous

@JohnRennie In case you're around, any idea what iterator() method do in Iterator<String> itr=list.iterator()? I looked around the net but they are all giving vague answers. The whole code is here. Iterator is an interface. I get that. But there doesn't seem to be any method body for iterator().

2:26 PM

I have heard good things about 3B1B but I have never watched a single video of them.

@heather its called the "singlet state" try wikipedia en.wikipedia.org/wiki/Singlet_state ... ps have collected some cool undergrad papers on BBO/ bell experiments over the years, very impressive

@BalarkaSen their videos are really good.

especially their linear algebra videos, though i know they have some calculus ones too - haven't watched those yet.

I can believe that

i have the attention span of a bug to watch through a worthwhile youtube video. all i watch are garbage trash lol

@Blue list.iterator returns an iterator object that can be used to step through the list.

@heather back...

@heather how can I be of assistance?

2:29 PM

@ZeroTheHero okay, so first, would the answer change if I specifically said that I'm looking for what SPDC does to the polarization for the photon?

especially quality trash like this

Anonymous

@JohnRennie Ok. What and where is the implementation (method body) of the iterator() method? I couldn't find it...:/

oops re drone racing ~~CNN~~ meant ESPN espn.com/espn/story/_/id/19100909/…

and also, would it change if i'm representing the photon going through as $\lvert\psi\rangle = \alpha\lvert 0\rangle + \beta\lvert 1\rangle$?

@heather Use \lvert instead of \mid for kets to not get that space between the | and the label of the ket.

2:32 PM

@heather ok... first a disclaimer... I'm not an expert at this so my info will be second-hand. second... let me remember how to start the MathJax app...

@ACuriousMind thank you

@Blue iterator objects all have the same methods. The idea is that whether you'r stepping though a list of strings, numbers, or whatever the iterator works in the same way.

In this the case the actual code is supplied by the list class, because only the list class knows its internal data structures and therefore how to step through them.

So list.iterator() returns a pointer to an object implemented by the list class.

see also java for-each iterator, added later in language geeksforgeeks.org/iterator-vs-foreach-in-java

@heather I do not know the answer to your new question. As far as I know the formalism does not have a polarization index, which suggests that the SPDC do not act on the polarization degree of freedom. However, there could be newer materials that do.

Anonymous

@JohnRennie You mean the iterator() method is defined in the ArrayList class, right?

2:37 PM

@heather my experience comes with working with experimentalists and this kind of question never came up.

Anonymous

I hope I can find the source code for that...

@ZeroTheHero SPDC doesn't change the polarization of a photon?

Assuming that in your example the variable list is of type ArrayList then yes the iterator() method is implemented in the code for that class.

to be honest, that doesn't make much sense to me at all.

@heather I don't think so but I've only worked with unpolarized photons anyways.

2:38 PM

@heather it shoots out photon pairs with correlated polarizations, so to speak

^right

Anonymous

 public Iterator<E> iterator() {
 return new Itr();
 }

there should be some sort of effect on the polarization because it correlates them.

Anonymous

huh...what's Itr() now (?)....*googles*

I think at @vzn is answering a slightly different question.

2:41 PM

@ZeroTheHero "the polarization of a photon" is a measurement.

@heather it is clear that the sources produce correlated polarization, but if you shoot polarized photons in I'm not sure the crystal would spit out photons with the same polarization as the input...

right (I'm not sure either there), so again there must be some sort of effect in that case on the polarization.

@heather the crystals need to absorb first the incident photon, and this may depend on the polarization, but this would affect the conversion rates rather than the output polarization. ** please ** do not take my answer as necessarily correct. I've only done calculations with unpolarized photons.

@heather are you studying some particular experiment?

@heather digressing a bit I can say with confidence there are polarization-preserving beam splitters, but I'm just not sure about polarization-preserving SPDCs.

2:44 PM

@vzn i'm researching to build one of my own

2

it could very well be that @vzn has more expertise than I on this topic.

@heather @ZeroTheHero The actual, full Hamiltonian for SPDC can be found e.g. here.

i think i might ask a new question on the main site - i really do appreciate your help though.

tl;dr: It's a non-linear optics mess :P

@ACuriousMind thank you...i'll take a look at it

oh dear

this is...madness

2:47 PM

In the end I think that whatever you are trying to do @heather, you do not actually want the Hamiltonian description of the SPDC process :P

You know that you put one photon in, and get two photons in a certain state out. What do you need the description of the process for, actually?

@ACuriousMind it's quite manageable without polarization, especially in the parametric approximation.

@ZeroTheHero Yes, it is, that's what you showed in your answer

but I think this paper shows well the complexity of the problem when you try to include everything.

@ACuriousMind @heather The paper is interesting. I'll ask "my local experts" if they can provide a simplified answer. This may take a few days.

@ZeroTheHero lol whoa there have just read a ton of related papers/ books etc and do not consider myself a QM expert. liked your answer to heathers question.

@heather could you produce a crisp question that I can cut-and-paste in an email?

2:50 PM

i can try:

@heather thats fantastic. however its probably a few hundred dollar experiment at the minimum. would really like to see someone succeed at this whos not nec at a university.

@heather I'll certainly pass it around. I had a long discussion with a really knowledgeable colleague on Wednesday and he owes me some simple answers. :)

What is the mathematical representation of the operation that type I SPDC performs on the polarization of photons, with a photon being represented by $\lvert\psi\rangle = \alpha\lvert 0\rangle + \beta\lvert 1\rangle$ (i.e., the standard representation of a qubit in a quantum computer)? Would the representation be dependent on the dimensions of the BBO crystal(s) used?

is there any particular detail that would be useful to add?

@ZeroTheHero thank you, by the way, i really appreciate it =)

@Kaumudi.H Good song

@heather ok I got it... I'll start with this and do my best to get back to you by end of week... keep in mind our academic year starts Tuesday so it will be unmanaged chaos early in the week.

2:54 PM

@heather there is some connection of singlet state to QC see eg arstechnica.com/science/2010/01/…

@ZeroTheHero ok. thanks again!

@vzn What do you mean by "singlet state"? A singlet state is a name for any state that sits in the trivial representation of some group.

@heather just so that we're clear: your input are photons with set polarization. The output will be photons + 2 more with possibly different polarization.

@ACuriousMind how do you randomly know this specific Hamiltonian

@0ßelö7 The power of Google.

2:57 PM

@ACuriousMind it applies to photons/ qbits. cf wikipedia article just refd for heather above

@ZeroTheHero my input is photons from a pump, and the output is entangled photons, i thought

@ACuriousMind singlet here refers to "polarization singlet". Since the polarization degree of freedom is isomorphic to spin, this is equivalent to SU2 singlet.

@ZeroTheHero Ah, indeed. Thank you.

@heather the pump will still be there, minus one photon. Your output will be (pump-one photon)+ 2 SPDC-produced photons.

okay.

yes, that makes sense.

2:59 PM

@heather maybe your dad could help out...? trying to remember did/ does he work in optics?

all right... let's see what I can drum up. I'm actually curious as well.

@vzn yes, he did quite a bit of work in optics.

but mainly classical, linear things...believe me i've already asked him some of this stuff.

@heather would like to volunteer my assistance for your prj in some degree possible, am excited by the possibilities, have wanted to do one myself for many yrs. however keep in mind (afaik) nobody outside of a university has ever done a bell entanglement experiment. and some of the earliest experiments (aspect, 1980s) cost in the $100Ks. the cost has been brought down substantially (to "near-tabletop") but unf it may still be substantial...

sure. i have money i'm more than willing to put toward it (all in the name of science! =D)

however, the experiment i'm planning is not exactly a bell experiment, though i'd be able to do one with the equipment i'm hoping to get ahold of.

@heather actually another idea, suspect a kickstarter or patreon or gofundme might work for this...! what experiment do you want to do?

@heather if hes worked with lasers, polarization, PMTs etc (typically used in classical optics) its most of what the experiment is.

3:09 PM

i'll be right back

@heather 4 undergrad bell experiments vzn1.wordpress.com/2015/01/26/…

googling, more recently found one at Rochester by Lukishova stl.asee.org/papers_2011/Lukishova.pdf

user228700

@BalarkaSen -_- Very nice.

3:27 PM

@heather a partial answer to your question might be found here: arxiv.org/pdf/quant-ph/9810080.pdf: "On the way to the fibers, the photons passed a half-wave plate and the compensator crystals necessary to compensate for in-crystal birefringence..." so there is certainly an effect due at least to the birefringence.

(This is the "canonical" Bell experiment result: "This corresponds to a violation of the CHSH inequality of 30 standard deviations assuming only statistical errors.")

in theory salon, 1 min ago, by vzn

AI Analyzes Gravitational Lenses 10 Million Times Faster / nextbigfuture

3:43 PM

@vzn Thanks for the thought but given my position it is preferable if not too much is known about my personal side.

3:59 PM

@ZeroTheHero ok, understood. yet not a dealbreaker on this side. that consideration has arisen with other speakers. (know the feeling.) plz keep in mind pseudonymous speaker ok, there is ample precedent now, and you can still limit personal info in the session to what is comfortable. plz continue to keep in mind :)

4:30 PM

@ZeroTheHero thanks =)

@vzn i might be able to get some equipment donated, too - companies seem to like when young people get into science =)

Anonymous

@heather Convincing the companies that the project is legitimate and you are able enough to do it might be the tough part. Hope you get someone to recommend you. Getting in touch with local university profs might be useful too. Wish you luck.

thank you @Blue =) I'm going to need all the luck i can get

Mithrandir24601

@heather I'm reading you want to talk about SPDC?

yep =)

Mithrandir24601

In terms of equipment cost, the most expensive things are going to be the laser (do you have permission from someone? safety training?), the crystal and (if you want single photon stuff) the detector(s) and coincidence counter

4:42 PM

right. so the laser i've found one that i think will work on DigiKey for ~$50 - that's not including the power supply, it's just the diode. my dad already has some power supplies; one of them will probably work. i've also figured out the circuit to supply a constant current source to the laser which won't be too expensive. My dad will be watching my work with the laser (and everything really) as to make sure i don't injure myself. I'll obviously be getting laser goggles.

Mithrandir24601

@heather That's good :) What's the Watts? :P

20 mW

Mithrandir24601

(assuming a continuous laser)

@heather Yeah, that'll be fine for SPDC

here's the DigiKey page

Mithrandir24601

405 nm. Good :)

4:44 PM

i also found a very useful book that i downloaded at the university library near me that provides a good general setup for the crystals and such

Exploring Quantum Physics Through Hands-On Projects

2

Mithrandir24601

So type I SPDC?

yes

the book doesn't provide all the information i need, but it's actually quite practical and meant for the amateur so it's very useful.

Mithrandir24601

@heather That's good - what is it you're looking to know?

my first question:

> What is the mathematical representation of the operation that type I SPDC performs on the polarization of photons, with a photon being represented by $\lvert\psi\rangle = \alpha\lvert 0\rangle + \beta\lvert 1\rangle$ (i.e., the standard representation of a qubit in a quantum computer)? Would the representation be dependent on the dimensions of the BBO crystal(s) used?

that's right now my biggest question.

my other questions are related to sourcing some of the other components i need, but i can figure those out. and i'm sure other questions will arise as i begin to actually build it =P

Mithrandir24601

@heather So, first of all, $\lvert 0\rangle$ and $\lvert 1\rangle$ are ways of representing the state, right?

4:49 PM

right

Mithrandir24601

A good place to start would be looking at birefringence

As in, a crystal with 2 ordinary axis and an extraordinary one

Birefringence is the optical property of a material having a refractive index that depends on the polarization and propagation direction of light. These optically anisotropic materials are said to be birefringent (or birefractive). The birefringence is often quantified as the maximum difference between refractive indices exhibited by the material. Crystals with non-cubic crystal structures are often birefringent, as are plastics under mechanical stress. Birefringence is responsible for the phenomenon of double refraction whereby a ray of light, when incident upon a birefringent material, is split...

^?

Mithrandir24601

@heather Yep, the uniaxial one

okay, i'll take a look at that.

i'm a bit confused...how does this relate to SPDC?

Mithrandir24601

5:10 PM

@heather The axes used in different types of SPDC are the ordinary (o) and extraordinary (e) axes i.e. the basis is no longer 0, 1; but o, e (more or less)

And as a result of this, fundamental properties of the light depend on the axis of the light (this is non-linear optics after all...)

(when I say axis, I mean polarisation and when I say properties, I mean things like the momentum/k-vector)

Anonymous

@heather Do you have the pdf? I'd like to have a look

Anonymous

(If that's ethical :P)

Prathyush Poduval

@Blue Libgen :P

@heather birefringence = 1 ray in 2 rays out. the 2 rays out are the two photons in singlet state.

Anonymous

@PrathyushPoduval Oh! Lemme search

Prathyush Poduval

5:14 PM

libgen.io/…

Anonymous

Thanks! :D

Anonymous

I love Russians :'D

Mithrandir24601

@vzn This: "Birefringence is the optical property of a material having a refractive index that depends on the polarization and propagation direction of light" - light travelling along different axes have different speeds (we're no longer in a vacuum)

(again: axis=polarisation)

Prathyush Poduval

@Blue What? I dont think there's any rule like that..

@Mithrandir24601 right. BBO is birefringent. it was a ("relatively recent") breakthru for it to start being used in Bell experiments.

Mithrandir24601

5:16 PM

@vzn yeah

@vzn Depends what you mean by 'relatively recent' I suppose

@Mithrandir24601 Bell experiments started in the mid1980s or so, earliest by Aspect. BBO seemed to show up late 1990s. the earliest ones were with calcium (ions)...

Prathyush Poduval

@heather That QM experiments book looks to be very interesting, with very much doable experiments. How did you come across it, and do you have any other experiment books like it?

Mithrandir24601

@vzn Yeah, to me that's not 'relatively recent' :P

@PrathyushPoduval there is no hard rule on this but we much prefer if you keep direct links to possibly illegal material out of this chatroom

Prathyush Poduval

@ACuriousMind Okay, thanks for informing. Maybe you can delete it now, since I can't do it anymore

Mithrandir24601

5:22 PM

@vzn Actually, do you know who did the first BBO Bell test? I'm wondering if...

@Mithrandir24601 Gisin did a lot of work in this area. weihs was in his lab. was it you who just cited weihs 1998? that was a milestone experiment. weihs even recorded the data as large gb files & put them on the web for open science analysis. poked at them many yrs ago. =D

Mithrandir24601

@vzn I didn't cite it here. Possibly(?) in Uni stuff earlier in the year

2 hours ago, by ZeroTheHero

@heather a partial answer to your question might be found here: https://arxiv.org/pdf/quant-ph/9810080.pdf: "On the way to the fibers, the photons passed a half-wave plate and the compensator crystals necessary to compensate for in-crystal birefringence..." so there is certainly an effect due at least to the birefringence.

ah doing some quick googling, the prutchis authors of "exploring QM thru hands on prjs" have a web site/ blog/ bell section diyphysics.com/category/experiments/bell-test

Mithrandir24601

And you might be interested to know that this was the first:
Stuart J Freedman and John F Clauser. Experimental test of local
hidden-variable theories. Physical Review Letters, 28(14):938,
1972.

@Mithrandir24601 yes. think that was calcium ions. there are even rumors of an early "null result" test that went unpublished.

Mithrandir24601

5:32 PM

@vzn Well... I'd be surprised if not... I mean, doing a cutting edge experiment in physics and getting an ideal result first time? There's always something Not Quite Right That Needs Fixing

@Mithrandir24601 it used low cost parts, may have been Freedman/ Clauser. iirc it was mentioned in Infamous Boundary book by Wick. paper maybe circulated "behind scenes"... but nevertheless think its important to try to publish null results... think it could give some clue about imperfect optics vs QM idealizations. am suspecting maybe it had low efficiency or something...

@AlexKChen I'm not where I can look at it, but wouldn't a VPython curve be a list of points, each of which should have its own position?

Mithrandir24601

@vzn Yeah, this is a thing - due to birefringence, the different polarisations of the photons travel at different speeds, so if you want to do photon correlations, this introduces a delay that doesn't help, so needs to be fixed/mitigated in some way

@Mithrandir24601 the attenuating factors are rarely modelled/ probed in the theory or experiments. think thats verging on an oversight/ mistake/ shame. in fact would like to see the tabletop experimenters go in this direction. old idea of mine, would even like to pursue it myself. :)

Mithrandir24601

@vzn There's a (not very clear, but still good once made sense of) image on page 43 of this

@vzn What do you mean by the 'attenuating factors'?

5:41 PM

thx enjoy collecting those (undergrad/ lowcost/ tabletop stuff) am gonna write it/ collection up again at some pt xqp.physik.uni-muenchen.de/publications/files/theses_diplom/…

hello again and sorry; i was helping clean up the lab

@Mithrandir24601 think there is an experimental regime where the "x sigma certainty" decreases. what experimental parameters decrease sigma? suspect experimenters/ researchers are getting carried away in exactly the wrong direction... to start, efficiency of the optics/ detectors etc is a prime suspect imho...

@Blue yeah, i have the pdf, where do you want me to upload it?

Anonymous

@heather It's okay. Found it on libgen. :)

@PrathyushPoduval i came across it kind of randomly, when i was searching for information on spdc/building spdc systems, and no, i don't have any others like it, sorry.

Anonymous

5:43 PM

Seems like a great book

yeah, it really is!

Mithrandir24601

@vzn and what do you mean by 'x sigma certainty'?

glad you found it on libgen.

@Mithrandir24601 in the bell inequality violation (as reported in recent abstracts etc, 30sigma etc). experimenters are long trying to outdo each other in that. its an arms race... in maybe the wrong direction...!

@Mithrandir24601 thanks for the explanation - i didn't realize o/e -> 0/1.

i'll keep reading about it.

Mithrandir24601

5:45 PM

@vzn So, 1. How do you improve the efficiency without increasing the cost massively? 2. Why are you trying to do so 3. Why does it matter? You might not realise, but people are trying to improve this but it's not simple!

@Mithrandir24601 itd be great if you could drop by here sometime/ intermittently for more detailed discussion in this/ related areas, have met some others going in similar directions :) chat.stackexchange.com/rooms/9446/theory-salon

@Mithrandir24601 youre not understanding my pt exactly. researchers are trying to maximize sigma in their experiments. am suggesting minimizing it.

Mithrandir24601

@heather Yeah, the axes and angles of the crystal and the input/output light/photons can be messy and complicated to think about :/

@vzn You want to maximise the number of sigma you violate something by as a higher sigma means there's a much higher change you've actually got the result and it's not just a statistical chance thing

Of course you want to minimise the value of sigma...

Anonymous

I'm looking for an easy to understand book on Antenna Theory....any suggestions?

@Mithrandir24601 ok. getting terminology mixed up. am suggesting finding experimental parameters that minimize the bell nonlocality violation instead of maximize it

Mithrandir24601

@vzn Why???

5:52 PM

@Mithrandir24601 lol! think about it carefully. its the sound of 1 hand clapping :P ... can you even name such parameter(s)? & if you cant, wouldnt that be a massive oversight/ gap in (theoretical/ applied) understanding?

Mithrandir24601

@vzn But if you barely violate it, you'll only get maybe $1\sigma$, so you're almost as likely to not have violated as violate it...

@Mithrandir24601 think carefully, why should it be possible to violate or not violate it? what is the sound of 1 hand clapping?

Anonymous

amazon.in/Flirting-Dummies-Elizabeth-Clark/dp/0470742593/…

Anonymous

wauw :'D

Anonymous

I was looking for Antenna Theory for Dummies...and this is what came up XD

Anonymous

5:55 PM

antenna-theory.com

Anonymous

Anyhow, this website looks good

@Blue lol try the Phd level material instead, just read it, highly entertaining o_O :P amazon.com/Game-Penetrating-Secret-Society-Artists/dp/…

Prathyush Poduval

@Blue Thanks, I might need it in the near future :P

@vzn xkcd.com/800

3

Mithrandir24601

6:10 PM

@vzn Because the world's not classical... That's the entire point... You don't want something that's just quantum, you generally want as much quantum as possible... 1 hand clapping? If you really want an answer to that, I can put my hand next to the microphone and analyse the sound. It seems that you're trying to imply something here.

Perhaps instead of making roundabout statements that there's a reason, it's maybe a good idea to be clearer, because so far, I'm not convinced that it's a good reason and I'm one of the people dealing with stuff at least vaguely similar to this, so you're very welcome to attempt to convince me here...

and yes, I have came up with a formula for $S$ before

6:50 PM

@Mithrandir24601 still missing the pt some. is it possible the same experiment can measure local classical vs nonlocal quantum effects based on varying some experimental parameter? the variations in sigma over many experiments seem to me to hint exactly in that direction...!

1 hour later…

Mithrandir24601

7:54 PM

@vzn Let's take this through step by step - The 'Bell [most often CHSH] inequality violation' experiment returns a value $S$. Is this the experiment you're referring to?

8:29 PM

@AlexKChen :D thanks! "euler interpolation SUCKS!" was using a language called Dark Basic Professional. The Riemann surface was coded with three.js, and the "bullet block" thing was coded with processing.js (the same thing that KhanAcademy uses!! That's why I recommend it so much. Likewise the electron gun was mostly processing.js).

'Guys? The Town is supposed to be good, and I thou--' 'PHYSICIST STEPHEN HAWKING DECLARES NEW FILM BEST IN ALL SPACE AND TIME' 'No, I just heard that--' 'SHOULD SCIENCE PLAY A ROLE IN JUDGING BEN AFFLECK?' 'I don't think--' 'WHAT ABOUT MATT DAMON?'

@AlexKChen "bullet block" I also used Mathematica to derive some of the equations... it's all about using the right tools. My youtube channel also has C++ simulations, which is my go-to language for anything with millions of particles or any PDEs or scientific work.

@vzn And yeah, I would love to!!! Quals are the 25th/26th of this month so I'm not working on anything but those for the next 25 days or so.

Mithrandir24601

@SirCumference Only Hawking can't move his head that much :P

How much mobility does he have?

Mithrandir24601

@skullpatrol barely any :/

As in, I think he can move his tongue a bit

8:38 PM

:(

can they keep him alive on machines?

Mithrandir24601

Yeah, pretty much - his helpers feed him manually - it's not particularly pleasant to watch

(also probably rude)

(Pardon me, if that sounds insensitive)

Mithrandir24601

Ah, no sorry - I'm saying that it feels rude to watch them feed him

Right.

I think I broke ChatJax

It's no longer showing up for me

8:46 PM

That explains why he cancelled his recent talks @Mithrandir24601

Mithrandir24601

@skullpatrol He did? Aww :/ He's certainly not getting healthier :/

still, in spite of his poor health, it's impressive he's lived this long (not to be offensive; hopefully my meaning is clear)

I've been a fan ever since I watched A Brief History of Time.

Mithrandir24601

@heather I totally agree with you

ah, as wikipedia puts it - "diagnosed in 1963 and expected to live only two more years"

8:51 PM

at the age of about 21?

yes, diagnosed at 21

whew, he also had another close call:

> During a visit to CERN on the border of France and Switzerland in mid-1985, Hawking contracted pneumonia, which in his condition was life-threatening; he was so ill that Jane was asked if life support should be terminated. She refused, but the consequence was a tracheotomy, which would require round-the-clock nursing care and remove what remained of his speech

All shown in the movie.

Mithrandir24601

@skullpatrol What they don't show in that is how much he fools around...

Yeah.

Anonymous

I don't like people saying that "Hawing is famous because of illness" and that "there are several first-rate physicists who have achieved as much as him or even more". Heck, there's no other physicist in the modern times who has achieved as much as him and have had to deal with a life-threatening disease.

9:01 PM

::makes popcorn::

Anonymous

It's touchy. Feel free to change topic.

Nah, I'm just saying this is all very debatable :-)

Mithrandir24601

@Blue The reality is that he's intelligent and so knows how to put things to his advantage as much as possible. Yeah, he's famous because of both, but added to that is someone who knows how to keep in the public eye more than most (if not all) other physicists. You think you're controversial? :P

Did any of his children go into physics? @Mithrandir24601

Mithrandir24601

@skullpatrol I don't know...

9:14 PM

Yeah @heather diagnosed at 21 to not live to 23 :-/

Around the same time he met Jane.

Hi @dmckee

How's the baby?

@Blue Hawing?

never heard of him.

;)

Anonymous

@heather I suppose you are intelligent enough to spot the typo. Pardon me for the mistake though. I am typing from my mobile. It's difficult to spot typos here.

oh, i'm sure it was just a mistake; i was just joking around =) @Blue

no need to apologize or anything

Anonymous

It's okay :)

cool =) I'll try to avoid bad jokes like that in the future

(what am I saying? that's practically impossible for me)

Anonymous

9:25 PM

@heather :-)

Anonymous

dictionary.com/browse/hawing

Anonymous

Wow, that's a word :D

:O

Anonymous

haaawwwwwww

Anonymous

lol

9:28 PM

Stop your humming and hawing and get to the point :-)

Humming and Hawking?

A God who holds the world record for eating the most skateboards is greater than a God who does not hold that record.

Woah

Mithrandir24601

@skullpatrol That's relatively easily doable :P (Hawking's another term for falconry)

:-)

humming, hawing, and hawking

that feels like that should be an xkcd

Mithrandir24601

@heather Hawking hawking on a hawing horse while humming?

The humming Hawking hawking on a hawing horse?

9:42 PM

Humming Hawking hawking on a hemming hawing horse?

9:59 PM

goodness

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