1. Quantum computing and the entanglement frontier
John Preskill
Caltech Board of Trustees
31 October 2015

4. Quantum Information Science
Planck
Quantum Information Science
quantum theory
+ computer science
+ information theory
quantum
information
science
Turing
Shannon

5. Caltech and Information Science
Nanotechnology:
“There’s plenty of room at the bottom.”
Feynman
Mead
Very-Large-Scale Integration (VLSI):
Paradigms for the semiconductor industry.
Computation & Neural Systems (CNS): How does the brain compute?
Hopfield

6. Frontiers of Physics short distance long distance complexity
Higgs boson
Neutrino masses
Supersymmetry
Quantum gravity
String theory
Large scale structure
Cosmic microwave background
Dark matter
Dark energy
Gravitational waves
“More is different”
Many-body entanglement
Phases of quantum matter
Quantum computing
Quantum spacetime

7. ???
Quantum Supremacy!

8. Shell Game

9. Shell Game

10. Shell Game

11. Shell Game

12. Shell Game

13. Shell Game 1 2 3
When the Gorilla give thumbs up, and you look under Cup Number 1, you always find the ball.

14. Shell Game ? 1 2 3
What if the Gorilla gives thumbs up, and you look under Cup Number 2?

15. (Classical) Shell Game
When the Gorilla gives thumbs up & you look under Cup Number 1, you always find ball. ?
When the Gorilla gives thumbs up & you look under Cup Number 2, you find the ball ...
Always
Never
Sometimes

16. (Classical) Shell Game
When the Gorilla gives thumbs up & you look under Cup Number 1, you always find ball.
When the Gorilla gives thumbs up & you look under Cup Number 2, you find the ball ...
Always
Never
Sometimes

17. (Quantum) Shell Game ? Always Never Sometimes
When the Gorilla gives thumbs up & you look under Cup Number 1, you always find ball. ?
When the Gorilla gives thumbs up & you look under Cup Number 2, you find the ball ...
Always
Never
Sometimes

18. (Quantum) Shell Game A. Always B. Never C. Sometimes
When the Gorilla gives thumbs up & you look under Cup Number 1, you always find ball.
When the Gorilla gives thumbs up & you look under Cup Number 2, you find the ball ...
A. Always
B. Never
C. Sometimes

19. (Quantum) Shell Game Secret of the Quantum Gorilla:
Before deciding whether to give thumbs up, he checks the cups collectively, rather than one at a time.

20. Quantum entanglement ….
This
Page
Blank ….
Nearly all the information in a typical entangled “quantum book” is encoded in the correlations among the “pages”.
You can't access the information if you read the book one page at a time.

21. To describe 300 quantum bits (e. g
To describe 300 quantum bits (e.g., atoms), we would need more numbers than the number of atoms in the visible universe!

22. Caltech Course :
Potentialities and Limitations of Computing Machines
“Nature isn't classical, dammit, and if you want to make a simulation of nature, you'd better make it quantum mechanical.”

23. What’s in here? Problems Quantumly Hard Quantumly Easy
Classically Easy
What’s in here?

24. (Maybe. We don’t actually know for sure.)
particle collision
molecular chemistry
entangled electrons
A quantum computer can simulate efficiently any physical process that occurs in Nature.
(Maybe. We don’t actually know for sure.)
superconductor
black hole
early universe

25. Decoherence
Environment
( )
( )

26. Environment
Quantum
Computer
Decoherence
To avoid errors, we must prevent the environment from “learning” about the state of the quantum computer during the computation.
ERROR!

27. Quantum error correction
This
Page
Blank ….
Environment
The protected “logical” quantum information is encoded in a highly entangled state of many physical qubits.
The environment can't access this information if it interacts locally with the protected system.

28. Kitaev’s magic trick: sawing an electron in half!

29. Alexei Kitaev
Jason Alicea
Gil Refael

30. Institute for Quantum Information (IQI): Postdoc Alumni
Eddy Ardonne Nordita
Salman Beigi IPM
Robin Blume-Kohout Sandia
Sougato Bose UC London
Sergio Boixo Google Sergey Bravyi IBM Darrick Chang ICFO Andrew Childs Maryland Andrew Doherty Sydney Luming Duan Michigan
Omar Fawzi ENS Lyon Lukasz Fidkowski Stony Brook Steve Flammia Sydney
Alexei Gorshkov NIST
David Gossett IBM Sean Hallgren Penn State Patrick Hayden Stanford
Liang Jiang Yale Stephen Jordan NIST Liang Kong Tsinghua
Robert Koenig Munich
Debbie Leung Waterloo
Netanel Lindner Technion Yi-Kai Liu NIST Ashwin Nayak Waterloo Stefano Pironio Brussels David Poulin Sherbrooke Robert Raussendorf UBC Ben Reichardt USC Norbert Schuch Aachen Yaoyun Shi Michigan
Kirill Shtengel UC Riverside
Kristan Temme IBM Barbara Terhal Aachen Frank Verstraete Vienna Guifre Vidal Perimeter
Ling Wang Beijing Stephanie Wehner Delft Pawel Wocjan UCF Shengyu Zhang Hong Kong
40 former IQI postdocs hold faculty positions (or the equivalent).
18 US, 5 Canada, 10 Europe, 3 Asia, 2 Australia, 2 Middle East.

32. entanglement frontier!
Challenging the
entanglement frontier!
Quantum Information
Quantum Matter
Surface-spin
Quantum Optics
Mechanical Quantum Systems
1 atom

33. Jason Alicea, 2012
Quantum Matter
Theory
(Physics)
David Hsieh, 2012
Quantum Matter
Experiment
(Physics)
Andre Faraon, 2012
Quantum Optics
Experiment
(Applied Physics)
Xie Chen, 2014
Quantum Matter
Theory
(Physics)
Thomas Vidick, 2014
Quantum Information
Theory
(Computer Science)
Manuel Endres, 2016
Quantum Optics
Experiment
(Physics)
Fernando Brandão, 2016
Quantum Information
Theory
(Physics)
Stevan Nadj-Perge, 2016
Quantum Matter
Experiment
(Applied Physics)

34. IQIM Annual Retreat

35. iqim.caltech.edu/outreach
IQIM quantum animations in collaboration with Jorge Cham of PHD Comics. Over 1 million views so far!

36. Unveiling the qCraft mod to MineCraft at MineCon 2013.
qCraft has been downloaded over 3 million times from qcraft.org

38. WHAT’S INSIDE A BLACK HOLE?

39. Holographic Principle
All information inside the room is encoded,
in a scrambled form, on the boundary of the room.

40. Holographic Principle
This scrambled encoding may be a quantum error-correcting code. The emergent space inside the
room is robust against errors on the walls of the room.

41. Holographic Principle
Quantum entanglement holds space together.

42. Richard Feynman

46. (Quantum) Shell Game A. Always B. Never C. Sometimes
When the Gorilla gives thumbs up & you look under Cup Number 1, you always find ball.
When the Gorilla gives thumbs up & you look under Cup Number 2, you find the ball ...
A. Always
B. Never
C. Sometimes

47. From: Robbert Dijkgraaf at the inauguration of Caltech’s Burke Institute.

48. From: Robbert Dijkgraaf at the inauguration of Caltech’s Burke Institute.

50. iqim.caltech.edu quantumfrontiers.com @IQIM_Caltech