1. Putting Weirdness to Use
Quantum Technology:
Putting Weirdness to Use
This is an architects conception of the new Physical Sciences Complex on the campus of the University of Maryland. It will be a state-of-the art laboratory facility, with excellent control over temperature, humidity, air quality, and vibration.
Chris
Monroe
University of Maryland
Department of Physics
National Institute of
Standards and Technology

2. Quantum mechanics and computing atom-sized transistors molecular-sized
2040
molecular-sized
2025

3. “There's Plenty of Room at the Bottom” (1959)
Richard Feynman
“When we get to the very, very small world – say circuits of seven atoms - we have a lot of new things that would happen that represent completely new opportunities for design. Atoms on a small scale behave like nothing on a large scale, for they satisfy the laws of quantum mechanics…”

4. Quantum Information Science
A new science for the 21st Century?
Quantum
Mechanics
Information
Theory
20th Century
21st Century
Quantum Information Science

5. Computer Science and Information Theory
Charles Babbage ( )
mechanical difference engine
Alan Turing ( )
universal computing machines
Claude Shannon ( )
quantify information: the bit

6. ENIAC
(1946)

7. The first solid-state transistor (Bardeen, Brattain & Shockley, 1947)

8. Quantum Mechanics: A 20th century revolution in physics
Why doesn’t the electron collapse onto the nucleus of an atom?
Why are there thermodynamic anomalies in materials at low temperature?
Why is light emitted at discrete colors?
Erwin Schrödinger ( )
Albert Einstein ( )
Werner Heisenberg ( )

9. The Golden Rules of Quantum Mechanics
Rule #1: Quantum objects are waves and can
be in states of superposition.
“qubit”: |0 and |1
Rule #2: Rule #1 holds as long as you don’t look!
|0 and |1
|1
|0 or
probability p p

10. f(x) f(x) GOOD NEWS… quantum parallel processing on 2N inputs
Example: N=3 qubits
 = a0 |000 + a1|001 + a2 |010 + a3 |011
a4 |100 + a5|101 + a6 |110 + a7 |111
f(x)
N=300 qubits: more information
than particles in the universe!
…BAD NEWS…
Measurement gives random result
e.g.,   |101
f(x)
Good-bad-good. Exponential storage. X2 example of parallelism.

11. …GOOD NEWS! quantum interference depends on all inputs
Shor started it all

12. …GOOD NEWS! quantum interference ( ) depends on all inputs quantum
logic gates
|0  |0 + |1
|1  |1 - |0
quantum
NOT gate:
Shor started it all
|0 |0  |0 |0
|0 |1  |0 |1
|1 |0  |1 |1
|1 |1  |1 |0
quantum
XOR gate:
e.g., |0 + |1 |0  |0|0 + |1|1
superposition  entanglement
( )

13. Quantum State: [0][0] & [1][1]
John Bell (1964)
Any possible “completion” to quantum mechanics will violate local realism
just the same

14. Entanglement: Quantum Coins
Two coins in a
quantum
superposition
[H][H] & [T][T] H H

15. Entanglement: Quantum Coins
Two coins in a
quantum
superposition
[H][H] & [T][T] T T

16. Entanglement: Quantum Coins
Two coins in a
quantum
superposition
[H][H] & [T][T] T T

17. Entanglement: Quantum Coins
Two coins in a
quantum
superposition
[H][H] & [T][T] H H

18. Entanglement: Quantum Coins
Two coins in a
quantum
superposition
[H][H] & [T][T] H H

19. Entanglement: Quantum Coins
Two coins in a
quantum
superposition
[H][H] & [T][T] H H

20. Entanglement: Quantum Coins
Two coins in a
quantum
superposition
[H][H] & [T][T] T T

21. + Application: quantum cryptographic key distribution plaintext KEY
ciphertext

22. Quantum Superposition
From Taking the Quantum Leap, by Fred Alan Wolf

23. Quantum Superposition
From Taking the Quantum Leap, by Fred Alan Wolf

24. Quantum Superposition
From Taking the Quantum Leap, by Fred Alan Wolf

25. Quantum Entanglement “Spooky action-at-a-distance” (A. Einstein)
From Taking the Quantum Leap, by Fred Alan Wolf

26. Quantum Entanglement “Spooky action-at-a-distance” (A. Einstein)
From Taking the Quantum Leap, by Fred Alan Wolf

27. Quantum Entanglement “Spooky action-at-a-distance” (A. Einstein)
From Taking the Quantum Leap, by Fred Alan Wolf

28. Quantum Entanglement “Spooky action-at-a-distance” (A. Einstein)
From Taking the Quantum Leap, by Fred Alan Wolf

29. David Deutsch
“When a quantum measurement is made, the universe bifucates!”
Many Universes
Multiverse
Many Worlds

31. fast number factoring N = pq fast database search
David Deutsch (1985)
Peter Shor (1994)
Lov Grover (1996)
fast number factoring N = pq
fast database search
500
1000
1500
2000
2500
3000
# articles mentioning “Quantum Information”
or “Quantum Computing”
Nature
Science
Phys. Rev. Lett.
Phys. Rev.
2005
1995
1990
2010
Quantum
Computers
and Computing
Institute of
Computer Science
Russian Academy
of Science
ISSN

32. Quantum Factoring application: cryptanalysis (N ~ 10200)
P. Shor, SIAM J. Comput. 26, 1474 (1997)
A. Ekert and R. Jozsa, Rev. Mod. Phys. 68, 733 (1996)
Look for a joint property of all 2N inputs
e.g.: the periodicity of a function
𝑓 𝑥 =sin⁡ 2𝜋 𝑥 𝑝
x x x (Mod 15)
etc…
p = period
𝑓 𝑎 𝑥 = 𝑎 𝑥 (𝑀𝑜𝑑 𝑁)
r = period (a = parameter)
A quantum computer can factor numbers
exponentially faster than classical computers
15 = 3  5
= ?  ?
application: cryptanalysis (N ~ 10200)

33. Error-correction Redundant encoding to protect against (rare) errors
Shannon (1948)
Redundant encoding to protect against (rare) errors
potential error: bit flip
0/1
0/1
better off whenever p < 1/2
𝑝→3 𝑝 2 1−𝑝 + 𝑝 3
unprotected
protected
1/0
p(error) = p
𝑝(𝑒𝑟𝑟𝑜𝑟)=3 𝑝 2 1−𝑝 + 𝑝 3
000/111
potential error: bit flip
010/101 etc..
take majority

34. Quantum error-correction
Shor (1995)
Steane (1996)
Quantum error-correction
P0 C
C* P1
r =
|0 + |1
Decoherence
|0 + |1  /4{ |00000 + |10010 + |01001 + |10100
+ |01010 - |11011 - |00110 - |11000
- |11101 - |00011 - |11110 - |01111
- |10001 - |01100 - |10111 + |00101 }
+ /4{ |11111 + |01101 + |10110 + |01011
+ |10101 - |00100 - |11001 - |00111
- |00010 - |11100 - |00001 - |10000
- |01110 - |10011 - |01000 + |11010 }
5-qubit code
corrects all
1-qubit errors
to first order

36. Trapped Atomic Ions Yb+ crystal ~5 mm
C.M. & D. J. Wineland, Sci. Am., 64 (Aug 2008)
R. Blatt & D. J. Wineland, Nature 453, (2008)

37. Quantum bit inside an atom: States of relative electron/nuclear spin

39. “Perfect” quantum measurement of a single atom
state |
state |
# photons collected in 200ms
Probability 30 20 10
0.2
atom fluoresces 108 photons/sec
laser
laser
atom remains dark 30 20 10 1
# photons collected in 200ms
>99% detection efficiency!

40. Internal states of these ions entangled
Trapped Ion Quantum Computer
Internal states of these ions entangled
Cirac and Zoller, Phys. Rev. Lett. 74, 4091 (1995)

42. Antiferromagnetic Néel order of N=10 spins
2600 runs, a=1.12
All in state 
All in state 
AFM ground state order
222 events
Since we are able to image each ion individually using the camera, we can directly observe an increase in the number of excitations as we move to long-range afm interactions. For instance, with 10 spins, we can easily see the difference between when each of our spins is up and when each is down.
If we turn on our antiferromagnetic hamiltonian, we can then image our degenerate Neel ordered ground state. If we perform 2600 simulations of our AFM hamiltonian with a range of interaction parameterized by this alpha, we find
About 220 events for each of the ground states, or 17 percent probability of landing in the ground state. Compared to the probability of falling into these states at random, it’s clear that we’re still recovering some ground state character.
1:00 – 16:00
219 events
441 events out of = 17%
Prob of any state at random =2 x (1/210) = 0.2%

43. (see K. Brown) a (C.O.M.) b (stretch) c (Egyptian) Mode competition –
example: axial modes, N = 4 ions
d (stretch-2) 60
mode
amplitudes
b+c d c b
2b,a+c
a+b
c-a
b-a 2a
b-a
c-a
b+c
cooling beam a
a+b
2b,a+c
Fluorescence counts 40 2a a b d
carrier
axial modes only c 20
-15
-10 -5 5 10 15
Raman Detuning dR (MHz)

44. 1 mm

45. Sandia Nat’l Lab: Si/SiO2
Maryland/LPS
GaAs/AlGaAs
GaTech
Res. Inst.
Al/Si/SiO2
NIST-Boulder
Au/Quartz
Sandia Nat’l Lab: Si/SiO2

46. Photonic Quantum Networking
Linking ideal quantum memory (trapped ion) with ideal quantum communication channel (photon)
optical fiber
trapped
ions
trapped
ions

47. Single atom here
Single atom here

48. Quantum teleportation of a single atom
unknown qubit uploaded to atom #1
| + |
qubit transfered to atom #2
| & |
S. Olmschenk et al., Science 323, 486 (2009).

49. we need more time..
and more qubits..

50. Large scale vision (103 – 106 atomic qubits)

51. Classical Computer Architecture
1 layer of transistors, 9-12 layers of connectors
Interconnect complexity determines circuit complexity
Efficient transport of bits in the computer is crucial
ibm.com

53. Quantum Information Science
A new science for the 21st Century?
Quantum
Mechanics
Information
Theory
20th Century
21st Century
Quantum Information Science
Physics
Chemistry
Computer Science
Electrical Engineering
Mathematics
Information Theory

54. Quantum Computing Abyss
state-of-the-art
experiments
theoretical requirements
for “useful” QC
 20
# quantum bits
>1000
<100
# logic gates
>109
noise
reduction
error
correction ?
new
technology
efficient
algorithms

55. This is an architects conception of the new Physical Sciences Complex on the campus of the University of Maryland. It will be a state-of-the art laboratory facility, with excellent control over temperature, humidity, air quality, and vibration.

56. Quantum Information Hardware at
Individual atoms and photons
ion traps
atoms in optical lattices
cavity-QED
Semiconductors
quantum dots
2D electron gases
Other condensed-matter
single atomic impurities in glass
single phosphorus atoms in silicon
Superconductors
Cooper-pair boxes (charge qubits)
rf-SQUIDS (flux qubits)

57. BUT MAYBE NOT THESE GUYS!
You may have heard about D-Wave, the company that claims to have already produced a quantum computer
They are learning, the hard way, that making a quantum system big is very difficult

58. 1947
ENIAC
(1946)

60. Richard Feynman (1982)
We have always had a great deal of difficulty in understanding the world view that quantum mechanics represents…
…Okay, I still get nervous with it…
It has not yet become obvious to me that there is no real problem. I cannot define the real problem, therefore I suspect there’s no real problem, but I’m not sure there’s no real problem.

61. N=1028
N=1

62. www.iontrap.umd.edu JOINT QUANTUM INSTITUTE Grad Students Postdocs
David Campos
Clay Crocker
Shantanu Debnath
Caroline Figgatt
Dave Hayes (Sydney)
David Hucul
Volkan Inlek
Rajibul Islam (Harvard)
Aaron Lee
Kale Johnson
Simcha Korenblit
Andrew Manning
Jonathan Mizrahi
Crystal Senko
Jake Smith
Ken Wright
Postdocs
Susan Clark (Sandia)
Wes Campbell (UCLA)
Taeyoung Choi
Chenglin Cao
Brian Neyenhuis
Phil Richerme
Grahame Vittorini
Collaborators
Luming Duan
Howard Carmichael
Jim Freericks
Alexey Gorshkov
NSA
Undergrads
Daniel Brennan
Geoffrey Ji
Katie Hergenreder
ARO