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TEDx Talks
Published: 2014-11-27
Source: https://www.youtube.com/watch?v=TlmwLyeWv5M
has anyone here used your quantum devices today anyone yes I fear fear here is one of my favorites my cellphone it's literally my entire or here there but maybe some of you have used your TV or a laptop or perhaps you have used your iPad camera and maybe some of you are clumsy like me and you dropped one off your fancy devices and it broke and
then you had this powerful urge to take it apart and look what's inside and then when you did that you saw there's a bunch of electronics made up of tiny billions and billions of tiny transistors fundamental building brought blocks of these devices and in order to make those transistors work we need to figure out the science of semiconductors and to control semiconductors and build a multibillion
dollar industry we need to understand structure and interactions at the atomic level and that's quantum physics the study of the laws that govern microscopic objects like atoms and electrons and even photons which I particles of light you may have heard of another little invention Condoleezza quantum device so this amazing scientific theory called quantum mechanics has transform our lives today but my fascination actually started %HESITATION info
quantum physics it started in the stars so this image here may look familiar to you it's sort recall a solar spectrum it's what you see when you pass sunlight through a prism and it breaks up into all of its constituent colors this is being taken by %HESITATION powerful telescopes with very high resolution image and what you may notice is a bunch of dark lines and that's
not dirt or scratches or anything that's real booze are places where the light is actually missing and before quantum mechanics we didn't really understand why is it that they're the specific colors that are missing from sunlight well the reason they're missing is because that light has been absorbed by gasses surrounding the sun cooler guesses and the specific colors that are absorbed depends on what that gas
is made up is that hydrogen is it helium calcium and in fact using quantum mechanics we can understand the structure of different types of atoms hydrogen versus calcium versus any other element in the periodic table so then we know which of those particular items will absolve which colors of light so each of these missing our spots is like a unique bar code which tells us what
the atom it's so by studying the barcode we can figure out what is the gas rounding the sunlight US surrounding the sons so for me this was amazing here is a secret message encoded in sunlight abolish the composition of the sun and we can decode it with quantum physics but in fact that secret message is even bigger it's an incredible message about the entire universe and
the person who decoded it was a young woman named Cecilia pain in nineteen twenty five Cecilia Payne was a PhD student at Harvard actually back then %HESITATION in you know in the twenties you couldn't actually take classes at Harvard if you are a woman so she was enrolled in Radcliffe College what she did all of her observation than our studies at Harvard observatory and she was
studying different spectra just like the one I showed you but not just for the sun but also for other stars and all these different spectra they look different so those bar chords are at different places I'm just trying to understand what that difference was so she used equations from quantum physics and figured out something amazing all those differences in the bar chord was because all these
different stars had different temperatures but in fact by far the most common element in all those stars was hydrogen and helium there's a hundred billion stars in our galaxy alone and there's a hundred billion galaxies out there and using these equations from quantum theory this young woman was able to figure out something a universal property of all the stars and that is like figuring out the
chemical composition of the universe and this was actually quite surprising because back in that time people thought that the composition of the sun and stars was he very much like the earth so in fact Cecilia Payne didn't even believe her own results but very soon after her work others confirmed this and in fact indeed today we know that the universe is basically made of hydrogen and
helium with everything else just you know in very very small amounts including all of the elements we know here on earth so this was really an incredible thing %HESITATION and you know Cecilia pain she you if she presented this as part of her PhD thesis in fact it was the first beast you awarded to any student male or female at Harvard observatory what a way to
stop it she just to stay on at Harvard and continue to do amazing research and she taught courses but didn't quite know what to do with this Eunice as of this moment young new PhD who was of a female they weren't really sure what to do so they actually could not even give her an official title for the next decade or so and the courses she
taught were not even listed on the books finally I in in nineteen thirty eight they gave her the title of astronomer and then eventually in nineteen fifty six she became a professor at Harvard and very soon afterward she became the chair of the astronomy department in fact the first female chair off any department Harper that's a city a pain to push him she's not a household
name she should be but that's a different talk well what I was lucky I in fact did you learn about her story and her work when I was a graduate student myself starting out and it was of course very inspiring to me both her science and her of her experiences as a woman scientist her work brilliantly illustrated the power of this incredible theory called quantum physics
but also %HESITATION I learned something else I learned that in fact the fundamental laws of nature are accessible to everybody Miller female young or old known or unknown and that was a really important message for me back then when I was studied starting out so I followed my passion and eventually I earned my own PhD in physics not a first at Harvard or anything it like
that but the first woman in my family to do that and of course I choose to focus my research area in quantum physics but instead of starting the largest objects like stars I decided that I want to investigate though smaller scales the world of individual atoms so we cannot actually directly see an atom it's far too small but we can set up experiments where we can
shine a laser beam at a cloud of atoms and the atoms will interact with the laser light and they believe a shadow of that interaction in the light and we don't collect that light and analyze it and extract that shadow and from that we can actually construct a picture to see this actor here is such a picture from data deacon in the lap of my colleague
coal pulley essence at the university of Arizona so as you can see the picture shows the world of the atom which is represented by a sphere and the laws that govern the war despite a kind of world is the law of the laws of quantum physics and that's actually a very strange set of laws for example there's something called uncertainty principle it says that we cannot
know exactly where the atom is located on the surface so what you're seeing here is actually an image off likelihood read shows where the atom is most likely to be and blue where it's least likely to be and the other thing that we can do is we can actually engineer the surface of the sphere so actually create a world for that and for example of how
do we do that we'll use lasers and magnetic fields to control this world and one of the things we can do is we can insert barriers and we can %HESITATION changed the shapes of islands in this on the on the surface of this world so this white line shows a barrier that's control struck did so barriers essentially like a wall that you and I could not
actually cross and then what we can do is we can take many such pictures of the atom over time and we can put them together and make a movie so the first such movies of this kind ever made here's such a movie watch what happens that term is moving back and forth it doesn't seem to be seeing the so called a barrier and it's not actually
climbing over the barrier it's passing straight through it's an incredible quantum effects called quantum tunneling what you're actually seeing here is literally an item walking through a wall and that was of course an amazing scientific discovery for me and I was very excited but I did see another one of those secret included messages sent to us by the universe the universe is showing us that barriers
are meant to be crossed and further more quantum tunneling connects directly back to the stars if you look deep in the heart of stars the core that it's actually a powerful nuclear fusion reactor that's where all of the sunlight and energy is produced and some of that comes to us as %HESITATION sunlight from our star and of course we know that is critical for life on
earth but how does that nuclear reactor look well thanks to gravity the hydrogen nuclei in the corps combine the fuse together to create helium and that releases enormous amounts of energy but here's the problem hide in the plea I they have positive protons positive charges and as you know like charges repel each other so as you try to bring these hydrogen nuclei close together the push
against each other there's a barrier and energy barrier and the hydrogen atoms cannot cross that barrier but yet they can and the reason they crosses cross it is exactly because of quantum tunneling the tunnel through the barrier and are able to complete the fusion process from which we get light and energy so some light on earth and the reason that we have life on earth is
because quantum particles can walk through walls and now that we understand the physics of quantum tunneling we can control it and build amazing devices like scanning tunneling microscopes and tunneling diodes and these are amazing %HESITATION devices and cutting edge technologies bridges scratching the surface tunneling is just one of many incredible quantum effects that we are exploring now to try to build future quantum technologies for example
one two particles can get connected together in a powerful connection that we call entanglement so if you make a change to one of the quantum particles it instantly affects all the other particles no matter how far away they are in the universe and again we find that in order to understand while quantum theory and what it's saying about %HESITATION entanglement we have to question are very
fundamental ideas about the nature of reality in space and time itself and that's amazing but there is a nice side effect by exploring entanglement we have found that like tumbling it's a resource that we can use to build technologies so it's the fuel that we must have in order to build future cutting technologies like quantum computers or teleportation or maybe some technology that we have not
even dreamed off as yet so quantum physics has led us on an amazing journey of discovery over the last century we have been able to look into the hearts of stars it has led us to understand structure of the composition of the universe it has shown us new ways to think about barriers and connections through space and time and it has shown us that by studying
fundamental scientific %HESITATION laws of nature we get really nice side effects like cool technologies and awesome devices but for me my fascination remains those secret missed messages those encoded %HESITATION you know mysteries out there in the universe the universe very generously has left us clues all around us and we humans we get to be nature's detectives we are constrained to this planet we have limited resources
and limited knowledge and yet thanks to physics and and developing our theories we can expand our understanding to the entire universe what will be that next secret message that we will decode that will lead to breakthroughs in science as well as society I don't know and that is the most exciting part thank you
