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# Quantum Information

### Video Briefs

This talk by Patrick Hayden will provide a tour of some of the recent developments at the intersection of quantum information and fundamental physics that are the source of this renewed excitement.
Professor Patrick Hayden of the Stanford Institute for Theoretical Physics (SITP) introduces the science of quantum information.

Professor Patrick Hayden of the Stanford Institute for Theoretical Physics (SITP) introduces the science of quantum information.

Sandu Popescu discusses multipartite entanglement with the It From Qubit Simons Collaboration team at the Stanford Institute for Theoretical Physics.

Professor Leonard Susskind describes how gravity and quantum information theory have come together to create a new way of thinking about physical systems. From fluid dynamics to strange metals, from black holes to the foundations of quantum mechanics, almost all areas of physics are being touched by the new paradigm.

Brian Swingle of the Stanford Institute for Theoretical Physics discusses the latest research in Black Hole complexity and computational power at the 2015 SITP Templeton Conference.

Professor Mark van Raamsdonk of the University of British Columbia gives the Stanford Physics and Applied Physics Colloquium on October 13, 2015.

ER = EPR is a shorthand that joins two ideas proposed by Einstein in 1935. One involved the paradox implied by what he called “spooky action at a distance” between quantum particles (the EPR paradox, named for its authors, Einstein, Boris Podolsky and Nathan Rosen). The other showed how two black holes could be connected through far reaches of space through “wormholes” (ER, for Einstein-Rosen bridges). At the time that Einstein put forth these ideas — and for most of the eight decades since — they were thought to be entirely unrelated.

ER = EPR is a shorthand that joins two ideas proposed by Einstein in 1935. One involved the paradox implied by what he called “spooky action at a distance” between quantum particles (the EPR paradox, named for its authors, Einstein, Boris Podolsky and Nathan Rosen). The other showed how two black holes could be connected through far reaches of space through “wormholes” (ER, for Einstein-Rosen bridges). At the time that Einstein put forth these ideas — and for most of the eight decades since — they were thought to be entirely unrelated.

### People

Professor Hayden is a leader in the exciting new field of quantum information science. He has contributed greatly to our understanding of the absolute limits that quantum mechanics places on information processing, and how to exploit quantum effects for computing and other aspects of communication. He has also made some key insights on the relationship between black holes and information theory.

## Pages

One of the defining features of quantum mechanics is the Heisenberg Uncertainty Principle, which imposes unbreakable limits on our knowledge of reality. Despite these restrictions, quantum mechanical particles can do amazing things like exist at two different locations at the same time. Quantum information science aims to explore the nature of information at the quantum level, a world in which bits can be both zero and one at the same time and perfect copying is impossible.

At the practical level, quantum information powers forms of secure communication that are provably impossible in a “classical” world. Likewise, an intrinsically quantum-mechanical computer could efficiently solve problems that are intractable for any computer of more traditional design, the most notorious example being that a quantum computer could crack most of the codes used to secure the internet.

Quantum information researchers at SITP have played an important role in the development of the basic theory of quantum communication. They continue to search for better ways to protect quantum computers from noise and communications from prying eavesdroppers. A unique feature of the quantum information group at SITP, however, is its close integration and participation in research on quantum gravity and black holes. Stanford is at the forefront of exploring the role of quantum entanglement to the geometry of space, the importance of quantum error correction in black hole evaporation, and even the relevance of computational complexity to stability of space.