Leo Kouwenhoven
Quantum weirdness in technology
from molecules via teleportation to a quantum computer
QUANTUMMECHANICAL WORLD
CLASSICAL WORLD
fm pm nm µm mm m
Quantum mechanics, the theory for small objects
Solvay conference 1927, Brussels
Quantum mechanics, absurd behaviour in big objects
Quantum Transport Group 2012, Delft
Quantum superposition
chemical bonds are quantum glue from electron superpositions.
CH4 methane
Quantum superposition
Two different positions at the same time!
Colliding with itself (interference)
Entanglement
Entanglement
“Properties remain entangled over long distances.”
Teleportation !
A measurement HERE also changes the thing THERE ……instantaneously!
Entanglement
Einstein: “Haha… Spooky action at a distance. You see, quantum is wrong.”
A measurement HERE also changes the thing THERE ……instantaneously!
Entanglement
Feynman: “Shut up and calculate!”
A measurement HERE also changes the thing THERE ……instantaneously!
Entanglement
Me: “Let’s do it!”
Entanglement Teleportation
Entanglement Teleportation
Entanglement Teleportation
Quantum Teleportation “Transfer information over a large
distance without going there”
Philosophy
What does it mean?
Quantum theory gives extremely accurate predictions è Quantum theory is the best tested theory!! è We know how it works but not why it works this way.
Feynman: “Shut up and calculate!”
Single photon light bulb
100 nm"
100 nm"
Single photon light bulb
Majorana particles on a chip
quantum
nm µm mm m atom gadget
DiCarlo group @ TUDelft
quantum
nm µm mm m atom gadget
DiCarlo group @ TUDelft
Can we extend quantum behaviour to even larger systems?
Hanson group @ TUDelft
Can we make quantum behaviour more complex?
quantum quantum classical
nm µm mm m atom transistor circuit gadget
Photo’s © Miraceti, Luigi Chiesa, T137, Yukata Tsutano used under a Creative Commons license: www.creativecommons.org
Why a quantum computer?
Klassieke bits 0 of 1 of
Quantum bits = qubits 0 en 1 = |0> + |1> en =
What is a quantum computer good for?
15 = 3 x 5
There exits no classical algorithm to factorize numbers efficiently ! The problem increases exponentially in time with the number of digits.
91 = ... x ... ? 437 = ... x ... ? ???
200 digits 1 day (onmogelijk vandaag) 201 2 days 202 4 days 203 8 days 210 1024 days ~ 3 years 220 3.000 years 230 3.000.000 years
“hard problems” take an exponentialy long time to solve
van Meter et al 2006
time to factor a product of two primes
bits
Classical computers are useless! Quantum computers could do it!
Complexity of Quantum Systemen grows exponential
| 0 〉
| 1 〉
α| 0 〉 + β | 1 〉
1 qubit n qubits
2n degrees-of-freedom ! | ψ 〉 = c1 | 000 〉 + c2 | 001 〉 + … + c8 | 111 〉
Classsical: speed ∝ n Quantum: speed ∝ 2n
Parallel computing:
Example: for n = 100 the quantum speed 2100 = 1030
Quantum information: - encode information in photons - in quantum mechanics it is impossible to measure the information without changing it. => internet security. A prototype quantum intranet exists!
http://www.idquantique.com
© U. Geneva
Quantum computer: - more complex circuits - prototype quantum circuit in 2020 - a full scale quantum computer in ~15 to 20 years
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