Tuesday evening lecture with Alain Aspect

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Tuesday evening lecture with Alain Aspect
From Einstein to Wheeler: wave particle duality brought to light
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Fifty years ago, R. Hanbury Brown and R.Q. Twiss, invented a new method to measure the angular diameter of stars, based on the observation of correlations in light. The analysis of their experiment in term of photons prompted hot discussions, and eventually led to the development of modern quantum optics, based on photon-photon correlation experiments. Similar quantum correlations can be observed with bosonic and fermionic atoms. I will present such experiments, after recalling the significance of the HBT landmark experiment.
Keywords quantum optics
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and that brings us to at the last the official part of this evening which is the evening lecture the traditional evening lectures which is always a highlight of the 1st day of the health of conference and the speaker will be introduced by your call have York me I introduced me ask you the podium thank you very much it's a real pleasure and effective the 2nd begin tonight to introduce other spread this evening speaker of these 2 great meeting the last thing we should distinguish directors of researchers university but also a professor of physics at the Institute the people putting technique used by the show therefore we period in the life of the we started in quantum optics where on beautiful experiments looking at single photons the quantum nature of single photons and entanglement ensured that many of you you know this famous experiments on which he demonstrated for the 1st time the violation of Bellingham Wash for that purpose he also developed a single full-blown sources and these were really efficiently he has been groundwork for an important direction research now that we called quantum information processing work on this topic to 1985 then he should be the work of the joint group of "quotation mark continuity that equally to follows then imagined bearish and there he was associated with the framers work from optical calling I mentioned you the roulette I mentioned it to blow molasses and the 1 he left a note in these places the Supreme Court cooling that field is important for our present With gold atoms in diameter measured more accurately than ever then thanks to the endorse achievements we have appreciation navigation that In the beginning of the 90's he went back to to the edge of America during his 1st period beating Baltimore picked would lie in a special period most of his work is doing what he's doing is called a melodic with Madeleine In Paris he met with the Mets stable helium and you work with the stable helium at the that people look at you as you look the and he produced the 1st Bose-Einstein condensate better stable at the beginning of examples of at the office workers inedible fixed by the 1st demonstration of the Hanbury Brown twist effects With metal met a stable you did it 1st with all songs and later together with the reversal from the food group collaboration with fermions also and of the least space also is working on Anderson locally localization with work that's a research for other reasons enthusiastic teacher I mentioned to see if then there the usual lawyers they're available Drew to show how great fish and therefore we are very delighted but we have here tonight is or even to picture the person who had many awards but we like most various should be beyond me about this it's on to for the were few OK thank you York fall this kind of presentation thank you all of you for being quiet at least for 1 or 2 minutes yes I'm going to talk about the subject on which I worked many decades ago and of course now I'd like to speak about more recent words like for instance on this some localization of the truckload items you know these although optical potential all or the you'll mention a quantum optimal dates and the I'm not going to talk about that tonight but I want to advertise as you see know you don't see it but I should have put the rule all of are C which means that they people from both sold some of you are interested in working on other side localization of Federico that almost all wonderment please you can check with me I have a good European money which is not yet evaluated uh 2 2 from ice floes so tonight I'm going I decided when Yorke told me you know what it's going to be after the dinner and I Willie good dinner and he told me by Dutch from yes quite the and I must say that we have approved but you confused with the n-dimensional stumble also by it's at least as good as a senior Gina 4 incidents in America and but and I asked him with their lines and he told me yes and so I decided that I should not local too serious and too high things but I would rather speak about fencing which is and and which anyway a fascinating physique and goods equation of singular .period so of course you recognize these gentlemen the John Archibald Wheeler and engage you don't recognize these wines it's the 1 that usually you see much older but at the same it's out there and start at the time when the introduced the idea of British squandered an engaging you look at this and everything I'm saying tonight I recommend that you buy his book I'd get royalties from it and and everything is explained in all details and you can find a way to write programs for his students it's that the rights of the OK so what is it it about
it's about the nature of life and the question of what it is like make assassinated mankind humanity from long ago In the liquidity the energy here in Greece most of the models of flights where but but there was interesting enough there with to models In 1 live like we see here the Fed is anything but a cost With many these flowers on the the CoreStates particles of different colors this very interesting molding but there was another competing model in which it was the ire of the Observer which would send off the coast of the object and the particle come again the idea of brother of a right these little joke these kind of things they were thinking OK I'm not going to talk more about that basically because I don't know more and then when make could be Germans would make a big jump the middle-aged In the there were not so much conceptual but they did something very important big improvements in engineering for instance they invented looking-glass young people don't realize that you when you get a certain age you're very happy to be able to put correcting gasses known in front of your eyes and of course after inventing Menzies they invented this goal microscope was invented in this country etc. so this was a time of engineering more than concepts and then the for concerts came again in the 17th century homes Lacy correctly In French music begins and all comments and reviews of all their all the ways and he said he was superior to what an analogy with the riddles on the surface of the water and it was really a fantastic work but he was not directly because it was big man knew going to defend the yield was more than the model of light is made of particles and the prestige of new drug wars so and correct rates will be because of the understanding the motion of planets and also we must meet you also beautiful experience in in objects but with the prestige of Newton against what and I must say but there not but maybe as a French plan and with people country we could join to complain about the British people located so the question was more or less settled but the goal is made of plastic products like this made a lot of period and then at the beginning of the 19th century 2 really great Genesis young and establish without any doubt about the fact that life the wave and that for instance you can download if you read French there are still some people crammed with French in this country there is a long tradition and if you remember reeled from the website of the the community's Johnson various the meanwhile Finnair it's unbelievable he has no idea of what kind of way DVDs but all these seasonings forestation and differences diffraction everything he's there Yesalis everything except that he has no idea of the nature of the way and that wait for another half of a century until Maxwell establishes without any doubt that light Eastern Europe to my meeting with and so I asked old Kennedy ones by the end of the year 18th century of 19th century in the 1980 the question was they were losing more to discuss you know not relocating physics is complete now the only job that we we have these 2 murder of more and more uh with more and more small replaces Constance what actually was most appealing because say everything is understood except to knockouts and the 1st background was negative result of makers of experiment and see also not crowd was understanding the behavior of several capacity at low temperature and we know of course that the 1st knockout demanded a discovery or invention the militancy of relativity and the 2nd 1 demanded and invention of quantum mechanics so it was not stupid anywhere you the feeling that time not everything was understood about life and then the young guys came and in 1905 he wrote 1 of several fantastic papers when he introduced the idea that life is made of 1 of the least squandered elementary grains of energy energy H U 1 moment of the calls h you provide guided by city which was named full-blown later Congress and winning major quantitative predictions for the the football retreat effect and nobody interested the uh it's remarkable that when he was elected in the Persian Academy of Sciences In 1980 it is not certain about within of 2 years we still have the revolt also 1 of the German professor writing a report about Einstein and there is a clear statement sometimes Einstein in making is making bad mistakes like for instance introducing the idea of British squandered but has already done so many beautiful things that we are going to fall giving an elected anyway nearly the greater the chance that you see here but now they're all of them Medi-Cal explicitly say enough review of modern physics paper written then 20 years later that you can download it explicitly state that young boxers into experiments to prove that Einstein was wrong and after 2 years of hard work to prove that Einstein's photoelectric effect rule was the correct prediction OK and these beautiful piece of experimental physics and also a beautiful example of no prejudice of a box with an idea and changed his idea and finally you probably know that Einstein goal Noble Prize explicitly for the photoelectric effect not thoroughly focus so it was really an important thing and then we we know about condoms experiment etc. and there is no doubt that life is made of plenty of but of course Einstein was absolutely aware that there was a serious program even introducing his idea of quantum EU but you need wave model to describe a difference for opposition it's right to do so to reconcile the particle description wasted because wave phenomena like the particle of oral away when the ancestors equation in a way it's cold wave particles you I'm shy but gave no further In a fantastic paper language you download each you can find it easier to win its goal the size of a work conference there is no reference but it's called sizable conference in 1909 and standing gave a conference sizable and gave many the reasons 2 0 I knew that life is both a wave and the party and I want just mention 1 and I hope into rings a bell to several of you he was able to calculate different durations of radiation in 1 of the most difficult beautiful Einstein reasoning dates the vessel the risk of moving there is blood with regulation on 1 side there is spotted bouncing on the other side of the wall and the use of the phrase duration and Bose's thermodynamic of acute agree on all that could cost friends and then you can calculate the free and the result is written here and
Einstein correctly and that rates of tourists in the following way the 1st hour of the state is a term that we would have if it was roundabout bouncing on the wall is what we call them with the shot OK so it's a noise that kind of regulation you whether these varieties made of plastic and the 2nd there is a guarantee that you will die have the blood the regulation was made of wage maturing inquiry and so you want to be notes and all these randomly distributed the notes reserve in this kind of terror and say who went to the calculations at the stern of the 2 birds it means that life is both away and part of the state is absolutely fantastic we of course know that abroad later that relate to the 19 0 9 reversed the idea and see when I have something which is obviously a pot gold right and electron there was way associated with solar again the solution of question wave of the answer is it's vault is both wave and particle but of course you are not finished said not the end of the story because we can already be article during day with article arguing that the were exactly the same but How can we represent these words by major and this is the subject of the rest of the book before embarking In 2 of the problem but we have to face when we consider nite and I think this is we must always denied so when there are serious problems when we consider naively without incredulity but before embarking 2 will show you these problems I want 1st to mention that wave article annually which is at the root of the quantum revolution has been extremely fruitful you all that it is a very successful concept on which allowed the physicist to understand the structure of matter its properties and direction was I talking over the structure of matter if she told to Jericho Beach children ought to join malice like total Sweger modest to the that with a cater that you must then sees you must and seized that classical physics cannot render an account of the fact that matter is that stable you want all that in classical physics Martin is made up of positive and negative charges which attract each other and should collapse you need quantum mechanics to understand that matter is solid and of course you need quantum mechanics to understand chemical bonds at cigarettes at blessed several exotic stuff flights to fruit the properly dinner-table national state press you need when the mechanics to invent laser transistor or integrated system it's these were not invented by a guy in a variety of California and the training at random it was invented by the most sophisticated the status of their time if you don't master fully quantum mechanics you don't and then the laser you don't invent transistor redundant uh integrated secretes etc. and so we can say that wave article during the said the root of the information and communication society but when you consider all these cases you will easily recognize that it is always quantum mechanics applied to large ensemble you what zillions of electron and you described them with quantum mechanics you of zillions of photons emitted by the laser it's rights there are OK and then the question is dollars these beautiful way about duality molding of quantum mechanics does it works for a single particle and of course if you look at books like for instance a fireman textbook they tell you yes it works well except that he's just describing an experiment which had never done but this is the way describes so these I'll find this quite so he said OK we have a source which emits 1 article at the time and I do we ask repeatable outside camp each particle or be submitted in the same way as the previous 1 and the same way as the next 1 then they passed through .period go of course you know about perfectly well you pass through halls you of detector and when you scanner detected you find that the rate of detection probability of detection is modulated like that and we all know the end of the story because we observed that when 1 of them holds the scrolls that then there is no more modulation and so only reasonable interpretation is to say that for each particle each single particle we have a wave passing through both or and more as guiding the particle toward those rights fringes OK we know the story the disease have been fascinated by that seems the very beginning of the century oak the annals of British agent data in 19 0 9 is a fantastic experience it was a time where you know you Watson gentleman's aware aristocrats and we knew little bit of physics but they also like to enjoy life and this 1 was so your money he was a sailor and so he was looking for an experiment where it could go on a very long so the experiment is indeed necessary the experimented this is following it put a needle the alarm very much attenuated so much opinionated that in order to observe the diffraction pattern of the needle With a photographic plates it would take several months so he sets devices goes on sailing comes out comes back develops a photographic plates annual observes the part of any major back-of-the-envelope calculation and say there was only 1 foot on at the time operators so 1 foot on the the wave like and there was a war a series of experiments which Morris are on the senior idea you take a forced you attenuate denied so much that the average distance between the 6 the photons is much bigger than the size of the interferometry whatever rights you locate and basically except for 1 experiment all the experiments show ladylike behavior which means that even when foot on some version of separated you of a wave-like so should we consider that equation is settled and that fall short single particle demonstrate that you can find interference with single particles when when I began to think about this equation in the early eighties it appears to me that it was not the case at all for the following reasons everything we know in modern quantum of the smallest goes back to ground and would allow the explained is that when you want the new date but I believe whatever the initial idea after the attenuation you better described the meeting a success was the classical estates and acquire the classical state asked the same behavior as a true classic court electromagnetic waves so for instance if you look at the average value of the electric field operator in such a way that classical state then the the agent is just like a classical electromagnetic waves and if you look at the famous G 2 correlation function which is the correlation between and then if you write the correct 1 on from taking into account the fact that the weather was a classical state then the formula is exactly the formula you would write with the classical away actually want global teaches us is that when you it you name it but I don't expect to want something the avian like the single particle you are going to tell me what is returning all books except mine but the photoelectric effect none of them are several all the books order the photoelectric effect isn't folkloric effect but proved that you really need to introduce the idea of seeing the photo and separated from each other and this was the basic reasoning of lunchtime when he introduced the quantum 19 0 5 well from a modern perspective and this is explained in detail in my book From the distinctive
you don't need but ordered to quantise light to understand the fedora Creek effect there is a very clear model which is based on the silly classical molded all flight matter and direction in which matter is quantized them but life is OK and fall a detector in the quantized we take a very simple model which is an was around state and only itemized states we forget about the that states that is it's amateur of unfolds for the discussion then you say that you have an interaction between this quantum objects and the classical if if you do it in Mandaree 1st full of perturbation theory family burden would sit around and you can use a conclusion that ionization only happens if the frequency is larger than the work function divided by the Broncos stands at sit rights to the on all the features of the folkloric Creek effects are described by his mother and if you ask me but where does a candidate they age you or page bomber Garcons from it just comes from the shouldn't equation I've edge deep over the deep and because you of Acehnese yuan-dollar wave you of that age mark only got which comes naturally in the country so actually it is not true that the photoelectric effect forces you to accept the idea that the weather was separated for tones and stuff like that OK so should we blame each time should be should we say that we did not deserve the Nobel Prize at the receiver the answer is obviously not the cause you need to buys something to understand the photoelectric effect either like it or not and the 19 bullfight madam was not young people do not know the stories some of them do not know the story should remember that bore introduce 20 additional market only 19 so in 19 0 5 you want to do something Einstein decided day it could not decided to quantise not so he was perfectly right but from a modern perspective the folkloric trick effect doesn't force us to accept the idea is that we must describe week to be being asked made of independent so thinking a little more about that we came to the following idea let's suppose he added that I pretend that I have a source which it separated particles 1 after the other 1 separated for for instance somebody claims that when I in its way separated from it's OK how can I prove that I was well separated by optical where you can think all the a measurement of the time you put the detector here and deck of their 1 detector behind each horse and you said coincidence if varies only 1 article 1 article will be detected only once and you will never observed the joint detection Sosa rates of coincidence with these you these will be a test that 2 of only 1 article at the time Of course is because the idea of article that the single particle chemistry but in contrast if you want awaits you without but part of the wave in 1 hole on the back of the wait until the horse and if it behaves like a wave you will have John conviction there will be a certain probability to other joint detection full visa service with believe it or not but such an experiment have not been done before we embarked into this work with my student feeling and if you try to understand why it's probably because the particle nature is consider US soldiers for electron neutron outcomes would you OK nobody would care for checking that it is really particles everybody really believes that and in the case of claims life when people need not consider seriously the fact that maybe it was not single particle they consider that it was all just when the average distance between foot on its large and they went looking for wave likes effects was attenuated life but of course I have say have shown you these is really questionable if you think of attenuated so now I'm going to describe in more detail a kind of experiment with me and I assumed all the young Streets is nice but being speed there is even nice so at during the experiment because he dealt with the following week put a business leader here and we pulled 1 detective at 1 detector here and wondered that over there and the idea is that if I have a single photo then I will have the probability of John detection exactly equal to 0 In contrast if I have a way the wave speaking to and there was a sudden probably off joint detection which is different from 0 so we can make the best we can make an experiment to decide whether it is you on on 0 if you are a mathematician it's very easy to distinguish you from you but if you are an experimental physicist then there is equation of Arab ourselves that there are what does it distinguishes 0 from where fortunately we were able or to derive a relations which would set a very clearly needs between the 2 BA let's suppose that we have a ways away which is Papa the probability of joint detection is going to be proportional to the square although intensity of the right OK man speech probability of single detection will be proportional to the intensity of the right mn we have 1 of the many cautious Schwartz inequality for instance is 1 which especially trio which tells you that the average of the square the invented is bigger than all the quarter to the square of the average and when you consider the quantities which are on the left of the screen probability of John detection probably no single detection if you believe in the school she Schwartz inequality which applies to wave description of the experiment you expect that the probability of John detection should be bigger than or equal to the product of single probably for people when all the experimental technique of John detections it means that the joint detection cannot be less than the rate of accidental coincidences he wanted to is the rate of exceeding the coincidence so if it is described by the way that you cannot have had far less than 1 on the other hand if you really of a single particle or if you are serious about that then you seeing that ideally the probability of John detection should be 0 and even if there was some noise in the experiment you can hope that this probability of John detection is less than the 1 so the Criterium for about a girl like the idea is to check this quantity and check that it is less than 1 Xisco material but we derive at that time is used all the time nowadays with people we you know that single photon source becomes very popular and when somebody beats the forcing Clinton is a single photon source you get a murderous G and stays G. Torres and 1 approved but I have a single significant source these exactly this criterium but with right OK now 1st experiment we had a lot of fun doing this work we took a smaller emitting diodes In making purchases of a few nanoseconds and opinionated was neutral density so much but in the average 0 was banned in the minus bumper purposes you do the calculations meanwhile much energy wanting a person you could neutral density and to the point where you 1 my calculation that his a minus-2 Fulton burqas what it means of course is that 99 per cent of the time you going to observe nothing and 1 per cent of the time you are going to have 1 foot but it's not the end of the story because when we did the experiment here for testing whether or not you are joint detection with this very very at innovative versus what we found is far it costs to 1 with errors so it does not but on like a single filled acting activated light does not behave like kissing the food what is the explanation dome of the photo well it's quite
simple at the immunity light is described as of now the quizzical states and if you look falls the Fulton distribution in such a state such a status not nite and state of the number of there said this is the number of thought of his mother would want a member of the you want distribution which is a plus and in a plus oral a few of certain probably 1 1 4 2 and you other provided it was consultant which is basically quarters of probably wobbly wanted the square where there is a factor of 2 but would take care of the factor of it so basically if you have 1 foot you all of a sudden probably 2 of and so there is just enough of bears in my that from time to time is just very with there is 1 foot on 1 side and 1 foot on on the other side and then I of Suffern rates of joint detection sold landslide is definitely not made of seeing for and of course an escalation do we have the means to produce a single photon states of right folks states island state of the number of thought can we demonstrate the experiment only a single particle behavior for such states and the answer is yes of course if you want to win at a single photon is version take a single excited and wait and a single atom within each 1 Fulton and only 1 the programs at that time even if young people don't believe it that nobody knew how to accelerate the single that we have not developed all this beautiful animal technologies to the rights of and so at that time the only kind of soft people can consider was classical like tourists in which you have zillions of fat communities and so you other ways statistical distribution for the 1st people to really clearly isolate significant effect was John Clouser in 74 1 and experiments we joined detection which amounted to doing what I described here but you not quite involved with but the 1st people to book very clear experiment about guide was Kimball Dijon on Monday evening 19 77 I think yes of 79 77 what they did was having an upcoming meetings reduce the density and and so that'll mean density in the beam was so weak that by looking with a microscope objective they are the only 1 at all at the time in the field of view of the microscope objective and then they observe the sense light emitted by uses single atoms that what 1 of them coming the Mexican commutes the Rock and they could demonstrate the 1st evidence non-classical behavior that is at the age at which cannot be understood by a classical with OK what we need was a kind of translation for I'm OG also timber Bassiouny and Mondale experiments but rather than isolated single up In real we isolated single atoms on the time axes doing In outsourcing is a big complicated source which had been used for the test of base inequality and what so it's very involved but basically what the source because in that we have an economy with Minneapolis which are excited to win a prostate and once they're are in the upper states have no choice they must be made to Fulton's interrogative Prescott so you whether green photo and the violent and I find here is financing and also there were many items in meeting excited simultaneously and anything but the average rate of nation was about then it was a 7 Cascade exciting Persico and now then divided between 2 photos the green and the blue is only 5 1 0 6 so the average time between 2 initial is 100 nanoseconds and the time between 2 photos of the same amount is final circuit so if you know what you overlook the Nazis you have backpack green groups then nothing when do nothing brings group nothing so the idea was just always that on the time boys relating the foot so the idea was very simple we take the 1st Phil of the Cascade and then falls next 5 nanoseconds we are sure to love 1 and only 1 foot in the probabilities of than other atoms in its during the same time this morning after that it doesn't change anything to the reasoning so he's what we did and immediately murdering the artifact quantity the rate of coincidence 2 single coincidence with farms of thought equals 0 . 2 which is clearly less than 1 so we have demonstrated a very clear and correlation very clear practical ideas now I want to describe the model experiment you have seen how complicated
the source falls several relays are actively being made to the rights of now visible way
for having single photon Anita you of a microscope looking at the Avery you someone and you can Weezer consul microscope you can observe only 1 in there which is a molecule with a four-level system you send the laser person not the is excited to see above state of the the dollar transition here and then 1 for and then the next phase of voters and with 1 foot it's a little bit easiest and this is too simple but not the way if you want to review on this kind of more than single photon sorceress of beautiful review paper by loonies and initially missionaries working right and I don't know if he's president of mountains the rules but if he's here I would be happy to see him and there is also a beautiful all the beautiful review paper by the party and is all about and what I want to describe as an experiment was abandoned was 1 of these beautiful source it doesn't end in corroboration with a group of economic depression and to make a long story short we on the other side which is 0 . 4 2 which means that it is clearly in the single for regime and now both ways all fitted on here always the Moldovan experiment we are asking how said equation now that I am sure that I have 1 foot on and only 1 he what happens if I send a single photo union and therefore metaphor instead like this where Massenet and from that that what what we like observed here where go full-blown will either on 1 side or the other side and then I will observe no indifference or will I have a wave speaking to about American life so we did the experiment with are this was a beautiful and therefore a matter that would be of some US and the and the from and it was muted stationery and so the the firms in the 2 past was chosen by pushing or pulling 1 near a recipe is the here OK and so the extra amount was going the following way we would sure was a position that is to say chose the path difference and then we would observe how many accounts and then how many guns here and how many accounts in the all the output of therefore format then we would move slightly and then count again most likely encounter gain and this is a result of the merger if we wait . 1 2nd I teach .period basically you see nothing so we decided to be a little less than the rest of your little more passion rather than waiting .period once again we wait 1 2nd at each position and now I hope you can see I don't know how you see from fire but you begin to see a variety of modulation really looks like an interference pattern and now we were relieved so we went quiet we waited for 10 seconds of each position and now 2 of the beautiful modulation you of an interference pattern was a his delivery cost 1 so this same user the relations with a remarkable signaled to HMOs ratio shows that we have a wave like the idea wastes in the Falklands because it's the same source as was used to demonstrate that it goes either 1 side or the other way now I should using the experiment with a modern devised what we use the use of so-called Crane the reason so you of the light beam which is spread half of the being passes up and goes down after being goes down and goes that if there is 1 and only 1 full it will be detected either India 1 already too and we measure the I thought Parramatta and we find that it is indeed it is definitely unless someone so it's in evidence for the singer for the knowledge we do we put the CCD camera here and we sequentially do we observe fringes here because of the inherent prison is always normal Rabin gives you fringes of the we observe fringes where I can show you were recalled of the experiment as it was rewritten with the singer for devices so I hope but believe would be reliable U.S. cities so I
hope you're going to see clearly what happens here so what you see this as a signal or on the history of the camera which is here and this is the city sensitive enough to detect each single focal so when a single photon is recalled you see a bright spot already OK that's have lounge the experiment it's a real seeking and you see single photon arriving yeah and after a while you begin to see that they observed on what we are going to call off right fringes and you see how beautiful the signal is it's more and more clear that it is a beautiful indifference OK and I don't resist to accelerate a little bit and go to the end but the school directly to be on the lookout duty 40 days and easiest really done with this source emitting 1 and only 1 4th of the use of thought cost 0 . 7 OK so know about ways particle during the network's what can what can we say no when we stopped for a while and we think what have we done In the 1st experiments we send a wave and we show that it is that they could either here or there and we conclude that there is 1 and only 1 particle board and the particle boards either on 1 side or the other side In the 2nd experiment with the same sources said wave placards said everything was sent it here and now we observed an interference pattern and the only reasonable conclusion is that it's the stuff we call it the way it was speaking to pot and recombine so Of course we we have contradictory Magee's is its sweet on offspring does it go either on 1 side or the other side of the single most sites Tennessee and of course when you are really in despair you can always try to go and look into news war so you're going to and of course news was never very keen on what you know the story when it's a it's survival story you know of course news all was the defending a complementarity and among many things you wouldn't claim that clarity and truth where complementarity and made all its faults to all this is a very true things anyway if you will to news and reviews of all you'll find lost complementarity and you immediately realized that the experiments incompatible or you have to choose either you use Z's devices all you use not device there is no way to do 2 ways for enhancing the so when you read when you read carefully ball the more than you you cannot speak of assistance without speaking of the apparatus which is going to make America and the apparatus would bring or in the kind of behavior of the system and so on you say OK if I understand what he sees it might be that the photon behave according to the equation here was equation do you behave like a particle on and then the Fulton of course and and then behaves like a particle and then when you know when you put this system in front of the foot on the foot right and see how they are not going to fully and others them there and America and so now it takes the dressing of a wave and right away I it's a nice way of understanding the statement of war that it is a monitoring apparatus which determines the behavior of the but then the receiver laughter guys a student named John Wheeler what's the following equation is saying you are not to decide between these devices and not devised when the comparisons have been so you keep the ball operators January but the fact that the rise of the music what is equation that will us and if there was use a time of 2 independent passed 1st and then I will decide that the idea of real they chose experiments so can we besides equation of President 1st the fall that we slightly modified the our experiments in the following ways and I like appreciate that you can really they that this is equivalent to the previous when we saw the experiment which is in the upper part of the screen there is no doubt that if you detect light from the detective you won it last and if you detected on the is passed down nothing happens here the crossing of the provisions but of course in the 2nd experiment now view of administrator and so the only thing you have to do is to introduce all not introduce administrator after the football on busses of residents Of course we are fast but not that fast so we are not going to do it by hand but we have some kind of electoral optic device about but we can do so say dream also John action Wheeler was theories so he's always drawing the experiment you of here the waste bucket arriving been speaker waste progressing and he has not yet decided between the the question is which route all which is did you traveller around Buffalo if you think ordered seriously about the situation and what you want about the choice the twins all observing the interfere therefore a matter over which path equation the choice must be spaceflights separated from the moment when the full parliament passes president speed sold out the choice cannot affect the decision of the photo when it passes here these how we
have implemented expert it's an and the format in which you was a salts of single photon and then the single photon speaking to buy a kind of polarization in speed and now we have the 2 plot and the distances 15 it there's so he's a football to show we try to compete with the so-and-so Delaware sure you did bites so we should also help 15 his letter evacuating OK so it's not it's cheap but you need a pipe anyway because you don't want to October answer gave few of turbulence than you you you fall you remember systematic separation it's also easy to work and the from with separation between the for 15 and then hear the 2 our combined but the polarization of the October laws and so in order to observe and France you still have to rotate 1 authorization and these where you will do it with another Tropic moderator so when there is no shortage of that these with the nation detected the and the path 1 would finish and detected you want but if we deprive or damage on the electro-optical a switch which is here then we need support innovation and we observed we expect to observe difference now I don't you we must be sure that the decision to introduce a lot and would use instead there must be space like separated from the butcher and fall not we have a device here which is pompously name 1 poem Rundle noise generator which means that it is a phenomenon which is basically 1 like the something like a folkloric trick effect or something like that and we haven't always and when which chart when we are above the law is it's 0 1 when we have you know it's a 0 and this makes a decision either to introduce all not to introduce the speaker and the decision is made everything is synchronized with a clock and a decision is made basically when the fault this in the middle of the Inter from either he so often does trouble 20 ministers spoke so he how we do the experiments then of course we have a computer and we separated the case when the speed is introduced from the case wandered into the basement not introduced and also there is all the details we have a slides mechanical or not to change the past differences between the 2 boss and so we are going to prison but that are not so
fast I select all the cases when the beans splitter was introduced and the disease the probability of detection here all there as eventual parsley France and you other beautiful indifference With French visibility in all 94 per cent for people write beautiful optics try to think that this is an experiment waste separation for 50 matters between the 2 parts and in addition is absolutely not a monochromatic source it's very broadband source so you really have to work closely with Israel's past difference appeared so this is a beautiful achievement I can see because eschewed easily think I'm not doing the experiments myself and I want to be his students whether doing experiment at a ball just uh experiment took soul we observed wave-like behavior when the beans was introduced and of course
when it is not introduced what do we observed when we observed that there is no fringe but more than that we observe the perfect correlation between the fact that when we broke this past basically there is no counts here and all counts are and vise versa when we broke this 1 almost everything is detected Shia these which will permit the which is technical permitted to see that it is almost perfect OK so what do we conclude that the the Fulton troubles 1 route on the other end weekend then which has been followed by the phone so what can we conclude where I'm going to let John Wheeler conclude because yes dutifully English certainly better than mine so I hope you're going to appreciate sold by these a conclusion of John Wheeler 1 decides the full commission Lufkin by 1 route or by both food after the test or that struck the at I think there was not much to what they can repeat another time no 1 besides you here and you decide that the photo of Africa by 1 route about both after the travellers finished isn't that beautiful and I think there is no other conclusion to draw from these experience Of course I know that you are a hotly your drink some wine and but I would not like to spoil the rest of you evening and I just scratched you most you head so I would like to make some comments we are which reinsurance Of course experiment artifacts false asked what set this way particle annually it's impossible to reconcile Wisconsin stand in major coming from our microscopic where that 1st comment very important that you must make to all students when they currently costs in quantum mechanics and they begin to Western equation although when you have your which tells you Hey you physicist you are not serious people want you that is the way you see that it is a way of white you ride that is about to call you see that it is a particle Hoddle system the formalities is totally consistent when you use the formalism of quantum optics asking this described in many good textbooks including a the families of quantum optics asks single this crucial for both experiment in equations you don't have to choose both behavior are embedded in the formalities it's only when we insist on having major but then you have to choose in 7 days it's a wave-like image in all the cases it's particle like I must say that is where where I haven't Nagy's which are inconsistent but I know how to manage and when I finished I say maybe this strange situation will be addressed then I think formalism and with deformities was there is no doubt the formalism school so is a good point 2nd I'm a joke but boss complementarity is a serious thinks it's avoid logical order inconsistency it is true that you cannot do that which for but what do we learn by the Daily chose experiment we learn that lost complementarity is certainly more subtle than just the apparatus changing the object and from this point of view I would encourage you to avoid them invoking the highs and their microscope when you teach quantum mechanics because eyes and a microscope suggest that you whether mechanical action on the quantum objects in order to make the result could be these not true example like this 1 sure that it is more subtle than the murdering apparatus just having an action became kind of mechanical action to make sure that the system changes you of the quantum erasers in all these said equation which clearly show that yes ball complementarity good but it's certainly not a simple in now after conclusion something which has grossed all my life addressing fundamental equations May at the end of the day producer unexpected applications and in that case the application these quantum cryptography you are the quantum cryptography the idea is to communicate that are being sure that there is no spies deserves and to make a long story short why single photon very efficient for quantum cryptography it's official efficient because when you were the 1 and only 1 photo then the all forced by the name is Steve but I refrain from putting a drawing of a beautiful woman because I have been attacked by the women will say that it is not nice OK because he always about the guy so woman OK so now I have the bad guy with a guy with a mustache and there are no problem anyway so you want despite here was trying to get information if you have stumbled wave packets there several Fulton you can take a little bit of information without being noticed because you of this some distribution but a few of 1 and only 1 foot if you take information you removed and then you leave a footprint here and normally they can check that is a spy observing on the right off was a real quantum cryptography is much more subtle than that but you can understand why using single photons is a very big advantage in quantum cryptography so just to show that it works and the people was warmly we corroborated the jump all conceded the largest operating and the winger quantum communication with singer for them at nite and to conclude to include them I'm old enough that I have seen these 2 things happen the data shows experiments is 1 of the 2 great quantum histories and here I use the words of fine and thinking about the storm great quantum mysteries unexpected applications came on the way the 1st mystery was written in the lecture hall physics we have already at least some chapter of electron physics and when fine and describes the scenery article experiment he writes is very strong statement we are going to examine a phenomenon which is impossible absolutely impossible to explain in many classical away and we just need the help of quantum mechanics in rarely the contains the on in history and it is a waste particle annuity for a single party but 20 years later in a famous paper which is a founding paper for quantum computation fine and realizes that there was something singers and the something Bonderman and if if you remember only 1 thing from the stroke there are really 2 totally different histories and quantum mechanics single particle with incredulity and and abandonment faulting but coral many particles that many people the quantum program it's there are it's totally different in nature of good and fine and realizes this and he writes about an abandonment and entangled particles and violation of those inequalities I haven't updated my several ways by squeezing the difficulty of quantum mechanics into a smaller and smaller parties so as to get more and more worried about this much teacher at nite it seems to be almost ridiculous that you can squeeze into a numerical equations but 1 thing is bigger than in all these business what is but there you are it is bigger than any logical argument that produce at and the beauty of that paper is that after realizing that immediately fine and proposes to use wonderful future policies will feature to be quantum computer so the message is studying from among the equations doesn't mean that it's not going to be application is just need smart people to realize that when was fantastic physical phenomena then it's very likely that at 1 point sensing would weaken out of it and to finish I want presented the people want them the experiments and I'm going to tell you why I like very much his photo so you of the people who did the experiments and in the back seat the godfather of the experiment that is to say the program he would experiment 9 the 1985 it opposes GCC's and I was a young PAG adviser so we were in the back seat of this experiment but what I like in this photo if that these guys these the 1st villages students of this 1 this 1 is a prestigious student and work and this 1 is officially the student that 1 and so it's a bit family and we all know that is it's a great tragedy than to worry about 40 of them thank you have Well thank you very much for the beautiful talk to choose how mysterious and beautiful field is really fantastic Willenhall due to see much I'm afraid some time between you and the party so you have all enjoyed the evening today have to do is more than just the bourse opened endured


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