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>> Under seats thank you for coming Good evening welcome to the bold ideas in physics lecture I am Fessor Parker from school physics I have the pleasure tonight of introducing. John Prescott who will be giving our lecture the bold ideas in physics lecture is in on or of Professor David Finkel Steen who is a beloved professor in the school a physics here.

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Dr Finkelstein worked on a number of issues I think that are related to what you hear about tonight in terms of the quantum structure of space time and actually some early work in black holes and quantum computation and material of of that nature. So our speaker will also be talking about similar topics is he Richard Fineman professor of physics at the California Institute of Technology I would say a well named institution so.

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John Prescott has a number of important awards to his name I just glanced briefly at the very long list and I will say it's bookended by the following he was the valedictorian of his high school and he is also the bold ideas in physics lecture at the Georgia Institute of Technology which is already up on his C.V. so he's very timely He's also by the way and A.P.'s fellow and a member of the National Academy of Sciences he's done work in quantum information although he started on cosmology and quantum gravity he got his 1st degree at Princeton University and then went to Harvard where he was a professor briefly before moving finally to Caltech where in addition to being the Richard Feynman professor he's also the director for the Institute for Quantum information and materials so without further ado I'd like to introduce John Prescott.

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Thank you very much Col and David Finkel Stein was a very remarkable physicists This picture was from around 1958 about the time that he was the 1st to articulate clearly what happens to you if you fall into a black hole what happens is that you can't possibly escape and you are drawn unavoidably to the dreaded singularity where you are torn to pieces by unimaginably strong gravitational forces it isn't pretty but it's it was brilliant and this is just one of David Finkelstein's bold ideas in a career filled with them so I'm honored to be giving this lecture named after him.

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And my topic is going to be bringing together 2 ideas that David Finkelstein was very interested in quantum physics and information we have information technology today which we think is very impressive but we all know that these will be replaced in the future by new technologies that we can't hope to imagine today it's interesting just the same to speculate about future information technology I may not be the ideal person to engage in that type of speculation I'm not an engineer I'm a theoretical physicist and I can't claim to be deeply knowledgeable about how computers really work but as a physicist I do know that the crowning intellectual achievement of the 20th century was the development of quantum theory and it's natural to wonder how the development of quantum theory in the 20th century will impact future information technology.

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Now quantum theory is a rather old subject by now but some of the important ways in which quantum and classical systems differ from one another we've only begun to appreciate relatively and relatively recently and many of those differences have to do with the properties of information carried by physical systems.

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To a physicists information is something that can be encoded and stored in the state of some physical system like the pages of a book but fundamentally all physical systems are really quantum systems governed by the rules of quantum physics so information is something that we can encode and store in a quantum state and information carried by Quantum Systems has some notoriously counter-intuitive properties that's why we like to speak about the weirdness of quantum theory and physicists relish that weirdness but we're also coming to ask more seriously these days whether we can put the weirdness toward Can we exploited the unusual properties of quantum information to perform tasks that wouldn't be possible if this were a less weird classical world and that desire to put the weirdness to work has driven the emergence of a new field what we called Quantum Information Science which derives much of its intellectual vitality from 3 central ideas quantum entanglement quantum computation and on America action and the goal of this talk is to explain those ideas but let's start at the beginning you all know that any amount of ordinary information what I'll call classical information can be expressed in terms of indivisible units and bits of information where you might think of a bit as an object like a ball which could be either one of 2 colors let's say red or green Now you can store a bit inside a box and then later on when you open the box again the color ball that you put in comes out again so you can recover a bit and read it.

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Now by quantum information I mean information carried by a quantum system and it too can be expressed in terms of indivisible units of quantum information what we call quantum bits or cube beds and for many purposes it's convenient and appropriate to envision a cubit as an object stored inside a box but we're now we can open the box through either one of 2 possible doors with those doors representing 2 complimentary ways that we can prepare or observe the state of our cubit and you can put information into a cubit through either door number one or door number 2 and then later when you open the same door again the color that you put in comes out again just as though the information or classical but if you put information into our number one for exam.