Also joining us tonight is a professor of chemistry at the University of California, Berkeley, co-director of the Berkeley Quantum Information and Computation Center and faculty scientist at the Lawrence Berkeley National Laboratory. She’s a fellow of the American Physical Society and recipient of awards from the Bergmann, Sloan, Alexander von Humboldt Foundations. Please welcome K. Birgitta Whaley.
Our third participant is a professor of physics at the University of British Columbia, a Simons Investigator and member of the Simons Foundation “It from Qubit” collaboration. He was a Canada research chair and Sloan Foundation fellow and was awarded the Canadian CAP-CRM medal for theoretical mathematical physics in 2014. Please welcome Mark Van Raamsdonk.
Our final participant is a professor of theoretical physics at Utrecht University in the Netherlands and winner of the 1999 Nobel Prize in Physics for work in quantum field theory that laid the foundations for the standard model of particle physics, one of the greatest minds of our era, please welcome Gerard ‘t Hooft.
All right, so the subject is quantum mechanics, and part of the evening will involve some challenge to the conventional thinking about quantum mechanics. And so before we get into the details, I thought I would just sort of take your temperature. Get a sense of where you stand on quantum mechanics. Is it, in your mind, a done deal? It’s finished, we completely understand it? Is it a provisional theory? Is it something which 100 years from now we’re going to look back on with a quaint smile? “How did they think that that’s how things worked?” So, David, your view.
DAVID WALLACE: Well I don’t think we fully understand it yet. I think it has a lot of depth left to plumb, and who knows it might turn out to be replaced. But right at the minute, I think we don’t have either empirical or theoretical reason to think that anything will take its place.
BRIAN GREENE: Good. Birgitta?
BIRGITTA WHALEY: I think it’s here to stay. There may be extensions, modifications, there may be something more complete, but this will still be part of it, in my view.
BRIAN GREENE: OK, Mark.
MARK VAN RAAMSDONK: Yeah, so there’s a frontier in quantum mechanics that I work in, and this is the frontier. It’s like the wild west of theoretical physics, where we’re trying to combine quantum mechanics and gravity, and we need to do that to understand black holes and hopefully eventually understand the big bang. And there’s a lot to do, and we don’t know if we’re going to have to modify quantum mechanics, or it will all be the same quantum mechanics all the way down.
BRIAN GREENE: Now, Gerard, you have unusual views.
GERARD ‘T HOOFT: Well yes, I could spend the rest of the evening explaining them. But, to my mind, quantum mechanics is a tool, a very important mathematical tool, to calculate what happens if you have some underlying equations. And telling us how particles and other small things behave. We know the answer to that question– the answer is quantum mechanics. But we don’t know the question, that’s still something we’re trying to figure out.
BRIAN GREENE: Good. So, sort of a jeopardy issue, if you know the American reference. All right, so just a quick overview. We’re going to start with some of the basics of quantum mechanics just to sort of make sure that all of us are more or less on the same page. We’ll then turn to a section on something called the “quantum measurement problem,” something weird, “quantum entanglement” as in the title of the program.
We’ll then turn to issues of black holes, spacetime, and quantum computation, which will take us right through to the end.
All right, so just to get to the basics of quantum mechanics. The story, of course, began more or less in the way that I started. We understood the world using classical physics in the early days, way back to the 1600s.
And then something happened in the early part of the 20th century, where people like – we started with Newton, of course, then we moved on to people like Max Planck, Albert Einstein. What drove the initial move into quantum physics? David?
DAVID WALLACE: I think it was really just pushing really hard at classical mechanics as it went down into the scale of atoms and the structure of atoms, and just finding that that structure snapped and broke. That trying to use classical mechanics to understand how hot things got or how electrons went around atoms without collapsing into the nucleus.
In all those places, we had a series of hints that something was amiss in our classical physics. And it took, I guess, most of 30 years for those hints to coalesce into a coherent theory. But that coherent theory then became not really just a single physical theory, but the language for writing physical theory, be it theories of particles or fields, maybe someday even gravity. And that language was more or less sort of solid by, I guess about 1930.