The new part here is creating two entangled light beams at wavelengths suitable for interacting with trapped atoms.
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.
I wonder what would happen if you sent the two entangled light beams through the double slit experiment, one through each slit. (I am not a physicist, this might be stupid)
What are the practical uses for an entangled light beam vs existing entangled particles?
Not much.
Yes, e.g. the phase of a photon from beam 1 may be highly correlated with the phase of the second (or, e.g. the polarisations may be highly correlated), but they will still behave as two particle beams.
(Yes, I am a physicist, at least I was 30 years ago;-0).
As others have mentioned, the double-split experiment is interesting in that when you leave a quantum system alone and let it travel through the double slit experiment, the interference pattern occurs. If you "force" an entangled system into a particular slit, then you don't have a quantum entangled system by definition; the entanglement comes from the quantum interaction of the system and how we can only describe it via an entangled wave function.
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 :-)
Kudos to you for accepting that it might be stupid. A lot of people say things with complete certainty these days when what they're talking about isn't in their area of expertise.
Not a physicist, but if you put one beam through each slit, it's no longer the double slit experiment. Instead it's just two single slits. So no interference pattern, just two spots of light.
Non physicist writing here, so maybe this is dumb.
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?
Speaking in programming terms, your program was called with two entangled arguments A and B.
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.
Entanglement is a correlation. A common example is putting clothing into boxes and moving them a light-year apart: if our box contains a left-hand glove, then we know the other box has a right-hand glove (and vice-versa).
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")
Entanglement is in fact much more vulnerable to interference than normal radio transmission - any interaction between the entangled particles and the environment quickly makes them decohere and become disentangled. This is in fact the reason why it's hard to make quantum computers - keeping a large number of particles entangled with each other is very very hard.
Side note: you are not the first to dream of this, there is even a word; ansible. Wikipedia tells me that Le Guin coined it for this purpose, I personally first ran into it in the Enders Game quartet.
Good question by the way, I appreciated the responses it generated.
It wluld be interesting to send one beam alternatively throught a linear or circular polarizer. Then you can check the polarization on the other beam and see if you have faster than light information transmission. With all the implications about causality.
Unfortunately you can't transmit information this way, even in theory. The polarizer has a 50-50 chance of testing one way or another, and the other beam will has the opposite polarization.
They did an experiment like this called the Quantum Eraser Experiment. The outcome is quite strange and I still don't know if I fully understand the result. It suggests potential retro-causality or at least superdeterminism or some kinds of weird time independent action. People will claim I'm just misinterpreting the experiment but I've yet to hear any explanation that doesn't hand wave some critical things away.
[+] [-] japanuspus|3 years ago|reply
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.
[+] [-] unknown|3 years ago|reply
[deleted]
[+] [-] sschueller|3 years ago|reply
What are the practical uses for an entangled light beam vs existing entangled particles?
[+] [-] plank|3 years ago|reply
[+] [-] ablatt89|3 years ago|reply
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 :-)
[+] [-] DJPocari|3 years ago|reply
[+] [-] Laremere|3 years ago|reply
[+] [-] lisper|3 years ago|reply
https://www.youtube.com/watch?v=dEaecUuEqfc
(Or https://flownet.com/ron/QM.pdf if you don't want to sit through a video.)
[+] [-] blackpanda|3 years ago|reply
Would it also form a pattern as the first one?
[+] [-] janandonly|3 years ago|reply
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?
[+] [-] Ralfp|3 years ago|reply
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.
[+] [-] chriswarbo|3 years ago|reply
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")
See e.g. https://en.wikipedia.org/wiki/CHSH_inequality
[+] [-] tsimionescu|3 years ago|reply
[+] [-] Kelteseth|3 years ago|reply
https://www.youtube.com/watch?v=BLqk7uaENAY
[+] [-] burnished|3 years ago|reply
Good question by the way, I appreciated the responses it generated.
[+] [-] AlessandroF6587|3 years ago|reply
[+] [-] n4r9|3 years ago|reply
[+] [-] schwoll|3 years ago|reply