Telephone interview, October 2022
“The conclusion is, yes, quantum mechanics resists all possible attacks!”
Telephone interview with Alain Aspect following the announcement of the 2022 Nobel Prize in Physics on 4 October 2022. The interviewer is Adam Smith, Chief Scientific Officer of Nobel Prize Outreach.
Alain Aspect was trying to find the limit of quantum mechanics, but, as he says in this call, “I didn’t find it!”. Recorded just after he had received news of his Nobel Prize, this conversation captures his thoughts about the place of his work in the long history of quantum mechanics, the need for constant questioning and reflection, and how he gets his head around the weirdness of quantum entanglement.
Adam Smith: May I speak with Alain Aspect please?
Alain Aspect: It’s me, hello.
AS: Oh hello, hello. My name is Adam Smith, I’m calling from Nobelprize.org, the official website of the Nobel Prize in Stockholm.
AS: Many congratulations.
AA: Thank you, it’s […] news.
AS: Quite lovely news. How did you receive it?
AA: Well, it’s of course a surprise because we know that there are so many outstanding physicists who deserve it and…
AS: It comes at the end of… I mean, not at the end, sorry… it comes as part of a great lineage of prizes in quantum mechanics…
AS: …starting, goodness, ninety years ago with the prize in 1932.
AS: That’s an extraordinary thought, isn’t it?
AS: Yes, and then… or ’21, I can’t remember.
AS: But then Heisenberg in 1932 for the birth of quantum mechanics.
AA: Yes, and then Heisenberg, and of course all these great names. Of course I am very impressed because I’m certainly not at the same level as these people who have really totally changed the physics. But then I am proud to be of the same league of course.
AS: Indeed. And it really speaks to the robustness of quantum mechanics.
AA: Yes. You know when I did these experiments testing Bell’s inequalities, at the end the conclusion is yes, quantum mechanics resists all possible attacks! In a sense my experiment was trying to find a limit of quantum mechanics, and we didn’t find it.
AS: Isn’t that extraordinary, what a creation by collective humanity.
AA: Yes, yes.
AS: And also the international nature of this prize to Vienna, and to you in France, and John Clauser in the US, speaks to the international effort that goes into all of this.
AA: Okay, it’s important that scientists keep their international community at a time when the world is not so nice, and where nationalism is taking over in many countries. So we have to do all efforts to keep scientists making international communities, there is no doubt.
AS: It’s a very important point. The phenomenon you studied, this quantum entanglement, is so weird.
AA: Yes. Absolutely, absolutely. And it’s so weird that as I presented in the Nobel symposium a few weeks ago, the fact that I am accepting in my mental images something which is totally crazy, which is nonlocality. Of course I know that nonlocality does not allow you to send a useful message faster than light, but in my mental images I have accepted nonlocality because otherwise I cannot even think of entanglement, except in the equations of course. But if I want to have an image, I put nonlocality in my image. Nonlocality is the fact that there is a kind of instantaneous relation between two objects, of course something that Einstein could not accept. But he had realised that entanglement meant that.
AS: Yes, this connection over unimaginably vast distances that is possible. Extraordinary.
AS: And of course your work settled the debates between Einstein and Bohr.
AS: So, again the historical significance of your work is amazing.
AA: Okay, I am glad you say that, but there is one point I want to make clear. When people say ‘okay, the debate between Einstein and Bohr was settled in favour of Bohr’, I like to say that Einstein owes a great, great merit in raising the question. And if nowadays we know so many things about entanglement and we want to use it for quantum technology etc we must give the credit to Einstein to have raised the question. So, for instance, I got the same year Niels Bohr Medal and an Albert Einstein Medal, and I think that it’s fair. There is not one who wins and the other one who loses. Bohr wins from a certain point of view, but Einstein wins because he spotted something extraordinary.
AS: And it’s always important to challenge.
AA: Yes, exactly.
AS: Thank you very much indeed. I notice something from your CV, which is that just before you did your PhD you spent three years doing Voluntary Service Overseas in Cameroon.
AA: Absolutely, absolutely. And you should know that it was essential because it is a place where I studied quantum mechanics in its modern formalism, in the book of Claude Cohen-Tannoudji, who got the Nobel Prize in 1997, and I studied by myself during this Cameroon period the book of Claude Cohen-Tannoudji, Franck Laloë and Bernard Diu, and when I came back to France I was ready to understand the various papers, Bell’s paper. Of course, John Bell, it’s a pity that he’s no longer there, but John Bell is a very important figure in that equation.
AS: Indeed. Isn’t that interesting, that life propels you onwards, and sometimes you have to just stop and take time for reflection.
AA: Yes, it was exactly… when I was in Cameroon I was teaching, but I had plenty of free time, and I used that time to… I knew that my education in quantum mechanics was not good at all. You know, it was the old quantum mechanics, solving partial differential equations. And the book of Cohen-Tannoudji, Laloë and Diu taught me where is the physics in quantum mechanics, and I was then ready to understand the discussion by John Bell etc.
AS: It’s a very important lesson for people listening I think.
AS: Yeah. Goodness, how do you feel about the prospect of all this attention that is focussed on you now?
AA: Aah! I will try to survive it. You know, my phone is ringing all the time, so I have set it down. This is why we have to go to a different phone in an office.
AS: Well, I’m very lucky that you took the time to do that. Thank you very much indeed.
AA: And I’m so happy, thank you very much.
AS: That’s good to hear, lovely.
AA: Thank you.
AS: Bye bye.
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