Researchers develop a light source that produces two entangled light beams
phys.org
phys.org
The general technique of creating entangled beams via OPO has been used for years at other wavelengths, and the resulting beams have been used for quantum optics experiments (including some rather spectacular ones).
What is new here is that by using light at wavelengths that can interact with trapped atoms, there is a possibility to use such atoms as quantum memory.
What are the practical uses for an entangled light beam vs existing entangled particles?
Pretty much this is the case. Trying to not get spun out of academia is hard work, due to the limited opportunities. Especially is you're unable to move beyond your own country.
Then the temptation of other jobs that easily pay three, four, fives times the salary creep in.
Banking in the city is probably the higher paid job in the UK
Far more frustrating and annoying is when people like that say things that are blatantly and provably wrong with complete certainty to an expert in the field and then actively refuse to hear any explanation or proof of the reality of the situation.
Based on my observations they seem to be usually perceived as correct by definition, but that [culturally trained and regularly reinforced] perception, and the methodology that produces it, is technically incorrect.
I made my comment based on having seen lots of HN commenters confidently dismissing various widely accepted (read: current best) physical theories based on appeals to intuition and specious or incomplete reasoning.
This:
"Unless that's being assessed by a "skeptic" who literally can't do the math required to fully understand the topic they're being skeptical about."
The subset of skeptics who "literally can't do the math required to fully understand the topic they're being skeptical about" (or in other words: aren't smart enough to form a non-incorrect opinion) are necessarily ("by definition") going to be incorrect.
While this sort of rhetorical, heuristic-exploiting language can be persuasive (because it exploits heuristics), it is often misinformative.
This can be easy to notice by replacing "skeptic" with various other categorizations (such as based on race, gender, religion (but often only certain ones)) - if one is to do that, the accompanying logic typically changes, &/or the person will take object level offence at the content of the analogy, causing them to be unable to appreciate that the modification to the topic has caused the logic to change.
> but nobody is claiming experts are infallible - that's silly.
I agree, hence I made no such accusation.
I'm curious why you brought this up - were you under the impression that I had done that, or were you maybe framing the conversation to make it appear that I had done that (which could cause 3rd party readers to have a negative opinion on my other words)?
> I made my comment based on having seen lots of HN commenters confidently dismissing various widely accepted (read: current best) physical theories based on appeals to intuition and specious or incomplete reasoning.
Well sure: skeptics, being humans, are often incorrect. But similarly, I've also seen lots of HN commenters who identify as ~"scientific thinkers" confidently dismissing various widely accepted theories (and various other cognitive errors) based on appeals to intuition and specious or incomplete reasoning. Consequently, I am "not a fan" of these sorts of people - however, the degree to which* various subgroups of people are guilty of various crimes is a very easy thing to get an inaccurate read on, since perceptions seem to necessarily rely upon substantial heuristic thinking (which makes sense if you think about it).
> The subset of skeptics who "literally can't do the math required to fully understand the topic they're being skeptical about" (or in other words: aren't smart enough to form a non-incorrect opinion) are necessarily ("by definition") going to be incorrect.
My post was intended to highlight my perception of the prevalence of a certain type of argument made in this context, and you're objecting to my description as if it was a logical argument. You are responding as if I am somehow logically comparing "experts" and "skeptics", as if one or the other category implies correctness. I didn't intend to make any such comparison, so I am left struggling a bit as to how to respond.
I intended to say, essentially: "In this context there are people working from incorrect assumptions and with insufficient knowledge, and it annoys me." You responded, essentially: "If people work from incorrect assumptions they are necessarily wrong, so that's a tautology." I don't believe that reasoning is either correct or helpful.
You are correct that I am using a number of heuristics, because that's how people generally communicate. In this case, I've seen a large number of discussions adjacent to the parent thread, and so I necessarily posses a heuristic to identify commonalities. The comment I replied to is not incorrect:
"Far more annoying, is when an expert is so mired in their professions dogma they lead those trusting them astray. The label "expert" is itself a counter to the skepticism and humility required to reliably maintain a grasp on reality."
That describes a real phenomenon, and I agree with the poster that it is annoying. I also see this sentiment overused and applied by people matching the heuristic I described, thus the comment. Ultimately, the discussion was a subjective comparison of the perceived relative prevalence of certain types of claims in online forums like this, and the attitudes of the posters about them.
To continue, you said:
> I agree, hence I made no such accusation. I'm curious why you brought this up - were you under the impression that I had done that, or were you maybe framing the conversation to make it appear that I had done that (which could cause 3rd party readers to have a negative opinion on my other words)
I'm certainly not trying to put words in your mouth, but I felt that you were trying to force me into a comparison I was not intending to make. The perception of experts as "correct by definition", to me, is orthogonal to the discussion which was going on. Sure, that happens and it's not correct. Nevertheless, working to develop reasonable heuristics about when to trust expertise is a rational thing to do.
> the degree to which* various subgroups of people are guilty of various crimes is a very easy thing to get an inaccurate read on, since perceptions seem to necessarily rely upon substantial heuristic thinking (which makes sense if you think about it).
I agree with that, and perhaps my attitude has also been unhelpful. To be clear, I don't have any sort of general opinion about how often "experts" and "skeptics" are correct, because those terms are vague and get used differently in different contexts, and because "being correct" is also pretty squishy if you drill down to any particular area. To make matters more confusing, I find that the most vocal anti-expertise skeptics are usually experts in something other than what they're skeptical about.
I'm not sure where that leaves this conversation, except that I think we differ somewhat in how useful we think heuristics are when reasoning under uncertainty and imperfect knowledge. This is also more abstract than I think is probably useful.
I'll try to explain inline...
> My post was intended to highlight my perception of the prevalence of a certain type of argument made in this context, and you're objecting to my description as if it was a logical argument. You are responding as if I am somehow logically comparing "experts" and "skeptics", as if one or the other category implies correctness. I didn't intend to make any such comparison, so I am left struggling a bit as to how to respond.
You were speaking colloquially (where inaccuracy is not just common, but culturally enforced).
Colloquial (inaccurate) speech is typically not realized as such, and thus spreads into other minds and is stored as facts.
Repeat for several zillions iterations, all the nodes in your network have a false representation and do not realize it.
This phenomenon is very harmful, thus I oppose it in principle and action. I would say: my normal actions are consistent with people's theoretical/intentional behavior. Of course, saying such things tends to invoke a negative reaction on the other end of the wire (/r/iamverysmart, etc), so I am attaching this additional idea to the ~offensive message (and as a computer guy, you likely are smart enough to understand what I'm talking about....except you and I are in an internet ~argument, which interferes with cognition....so hard to say what will happen - let's find out!).
> I intended to say, essentially: "In this context there are people working from incorrect assumptions and with insufficient knowledge, and it annoys me." You responded, essentially: "If people work from incorrect assumptions they are necessarily wrong, so that's a tautology." I don't believe that reasoning is either correct or helpful.
I don't disagree so much, but then "I made my comment based on having seen lots of HN commenters confidently dismissing various widely accepted (read: current best) physical theories based on appeals to intuition and specious or incomplete reasoning" has the appearance of being not correct/helpful to me (as someone who regularly disagrees with mainstream narratives, and has higher than average concern about the state of affairs on this planet).
>> "Far more annoying, is when an expert is so mired in their professions dogma they lead those trusting them astray. The label "expert" is itself a counter to the skepticism and humility required to reliably maintain a grasp on reality."
> That describes a real phenomenon, and I agree with the poster that it is annoying. I also see this sentiment overused and applied by people matching the heuristic I described, thus the comment.
The optimal level of deployment/distribution of this idea is not known though - it very well may be that it would be optimal to discuss this 10 times more often than we currently do. And while this "is" "pedantic", perhaps, it can also be very important simultaneously.
> I'm certainly not trying to put words in your mouth, but I felt that you were trying to force me into a comparison I was not intending to make. The perception of experts as "correct by definition", to me, is orthogonal to the discussion which was going on.
Where you consider it to be orthogonal, I consider it to be fundamental. It is the "water" in:
There are these two young fish swimming along and they happen to meet an older fish swimming the other way, who nods at them and says “Morning, boys. How’s the water?” And the two young fish swim on for a bit, and then eventually one of them looks over at the other and goes “What the hell is water?”
Or more technically/academically: https://en.wikipedia.org/wiki/Semiotics
> I agree with that, and perhaps my attitude has also been unhelpful.
Nor is mine! It's pretty rare to encounter someone who's interested in a serious conversation on such matters, so I mostly just "spread the good word" in a semi-serious and not very polite way....for me it accentuates the absurdity of the situation, and thus the enjoyment.
> To be clear, I don't have any sort of general opinion about how often "experts" and "skeptics" are correct....
I'd say: I bet if you could peel back your skull and see what's going on inside, it would be a LOT more complicated than this!
>...because those terms are vague and get used differently in different contexts, and because "being correct" is also pretty squishy if you drill down to any particular area.
Pretty squishy as it is. A not great analogy would be how it took a really long time to get from London to New York, prior to airplanes being invented.....the point being: humans can improve over time (though, they do not necessarily).
> To make matters more confusing, I find that the most vocal anti-expertise skeptics are usually experts in something other than what they're skeptical about.
If that! I'm a conspiracy theorist, so I'm fairly well versed in the substantial shortcomings of my brethren. "There but for the grace of God go all of us"....or so we like to think (that it has not already happened)!
> I'm not sure where that leaves this conversation, except that I think we differ somewhat in how useful we think heuristics are when reasoning under uncertainty and imperfect knowledge.
Well I think it is a lovely conversation!
> This is also more abstract than I think is probably useful.
Right, but how would one even go about accurately estimating utility for this sort of thing? Like: useful with respect to what? "Enjoyment"? According to mods, that's what HN is about, and going beyond that is "generally not advisable", for reasons that seem to be available only on a "need to know" basis (if you don't mind a little bitterness/cynicism).
https://www.youtube.com/watch?v=dEaecUuEqfc
(Or https://flownet.com/ron/QM.pdf if you don't want to sit through a video.)
I think in terms of practical use cases, generally for entanglement, it allows for high amounts of encoding since the particular basis used to describe each individual constituent becomes coupled with one another e.g. (|PsiA, PsiB> = (|A1> + |A2> + ... + |An>) * (|B1> + B2> + ... + |Bn>)) allow for a high number of configurations of a problem space to be encoded. I suppose there could be some interesting optical phenomena used for optical experiments/pulsed lasers but you'd probably need to discuss this with an optics expert :-)
Would it also form a pattern as the first one?
What I've read about entanglement is this: do something to a particle, and a predicable thing happens to another particle.
So, I am dreaming of a "radio" that has no interference because instead of agitating the electromagnetic field, it manipulates one particle. On the other end there is another "radio" that measures the entangled particle and turns the movement/spin/whatever of the particle on that end into data (voice/video), and vice-versa.
The problem, I guess, is the Heisenberg uncertainty principle (again, non-physicists so possibly there are workable cheats around this). So, measuring of one particle already changes it, therefore any incoming data is nullified?
Entanglement means that if you check for value of A and its true, then B is guaranteed to be false. But if you change A to false, system becomes detangled and now both A and B are false (vs B becoming true). This is why entanglement cant be used for FTL communication.
Also because in order to see what state is particle we need to interact with it, measuring its quantum state also breaks the entaglement.
The action that breaks the entanglement is the update of A before reading B and not the reading of A or B.
However, there's no way to create a radio using this correlation, since we can't effect whether we got the left/right glove:
- If we chose it before travelling, that would (a) require measuring which is which (i.e. opening the boxes), and (b) require choosing our message ahead of time, when the boxes are together (which isn't faster-than-light communication; e.g. we could just as well write our message inside the other box; no radio needed)
- If we re-arrange the fabric of our glove after measuring it, that would have no effect on the other glove (our actions would de-correlate them).
The reason this glove analogy breaks down is that gloves can be explained by "local hidden variables": i.e. if we see a left-handed glove, that could have been in the box all along; nothing weird.
The weirdness occurs in the correlations between different measurements. For example, if we put the clothing on our hand, we're measuring which glove it is (left or right hand); if we instead put it on our foot, we would measure which sock it is (left or right foot). Handed-ness is completely (anti)correlated: if both are measured as gloves, we always get one left-hand and one right-hand; likewise if they're both measured as socks.
Handed-ness and footed-ness are uncorrelated: if one piece of clothing is measured as a glove, and the other as a sock, there's no correlation between left-hand/right-hand and left-foot/right-foot.
Where it gets weird is when measuring somewhere in-between, e.g. if we measure 2/3 glove and 1/3 sock; and the other is measured 1/3 glove and 2/3 sock: their handedness/footedness is more correlated than classical physics can explain (in practice we measure the polarisation of light, which can be measured horizontally, vertically, or some angle in-between!). Experiments have ruled out "local hidden variables", like "it was always an X" (e.g. something like "the box always contained an 80/20 mixture of glove/foot, with respective left/right mixtures of 50/50 and 20/40"). Quantum physics correctly predicts those experiments (e.g. using "superpositions of left/right handedness/footedness")
Good question by the way, I appreciated the responses it generated.
As an even simpler example, let's say Alice and Bob need to solve a really hard problem that can be cleanly split into two parts, A and B. In round 1 Alice and Bob can't communicate but they have access to an entangled photon. In round 2 they meet and compare notes. If they choose which part to work on randomly, then in only 50% of the outcomes are both parts A and B solved when round 2 starts. If, on the other hand, they use the polarity of the entangled photon to decide which part to solve, then quantum mechanics guarantees that they both solve different parts. It's random and unpredictable which part gets assigned to whom, but in 100% of outcomes when round 2 starts, Alice has solved one of A or B, and Bob has solved the other one.
We can't transmit information instantaneously, but there are nevertheless certain distributed tasks we can do better at when we have a source of entangled states.
To paraphrase, Alice, Bob and Carol play a game where they can't communicate (after deciding on a strategy) and the referee shows each of them a bit. After being shown the bit they must reply with 0 or 1. The four possible combinations the referee chooses uniformly from is:
(Alice: 0, Bob: 0, Carol: 0)
(Alice: 1, Bob: 0, Carol: 1)
(Alice: 1, Bob: 1, Carol: 0)
(Alice: 0, Bob: 1, Carol: 1)
First, without using probability, if A0 is the answer Alice gives when shown 0 and A1 when shown 1 (and similarly for Bob and Carol), you get the following set of equations needed to win always:
A0 + B0 + C0 = 0 (mod 2)
A1 + B0 + C1 = 1 (mod 2)
A1 + B1 + C0 = 1 (mod 2)
A0 + B1 + C1 = 1 (mod 2)
Now, probability doesn't help here, because any mixed strategy can be shown to be equivalent to a combination of pure strategies, none of which can guarantee a win.
Yet with a shared entangled state, it can be won 100% of the time. This isn't a probability thing - you can actually guarantee a win using the quantum strategy, even over arbitrarily large distances.
The physicist won’t call this transmitting information, but the information scientist has no qualms about acting on random data. And once you give data meaning, it is information. Maybe both parties pre-agree that N zero bits in a row from the digitized reading of the entangled photons is a start signal, and the bits that follow are used to make choices in whatever action is carried out. Now the first party has “sent” an instantaneous message informing of their actions.
To be clear I don’t think there is a clever gotcha here. But it is helpful in constraining what is meant by information locality here.
That's fine and useful for some things, but as you say it's not fundamentally quantum and it's not what's exciting about this development imo.
A might know exactly what B is going to measure, after he's done his part, but that doesn't mean any information can be transmitted.