-
8/19/2019 From imaginary experiments to quantum information
1/57
Luis A. Orozco
St. Mary’s College, March 2013.
www.jqi.umd.edu
From imaginary experiments to
quantum information
-
8/19/2019 From imaginary experiments to quantum information
2/57
With special thanks to:
William D. Phillips
Howard J. Carmichael
Steven L. RolstonPablo Barberis Blostein
Ivan H. Deutsch
Work supported by
National Science Foundation
-
8/19/2019 From imaginary experiments to quantum information
3/57
time
s p e e d
Classical World
-
8/19/2019 From imaginary experiments to quantum information
4/57
50 micrometers
10,000X
-
8/19/2019 From imaginary experiments to quantum information
5/57
10,000X
The world becomes discrete … it comes in quanta
Quantum World
-
8/19/2019 From imaginary experiments to quantum information
6/57
It all started in the 19th century
-
8/19/2019 From imaginary experiments to quantum information
7/57
• Oct. 7, 1900
" # ,T ( ) =8$ h#
3
c3
1
eh# / kT
%1
Coffee and Cake with the Rubens
• The birth of quantum theory“an act of desperation…I had to obtain a positive result
under any circumstances and at whatever cost”
Max Planck
-
8/19/2019 From imaginary experiments to quantum information
8/57
• 1905 the “photon”, is the quantum oflight
Albert Einstein
-
8/19/2019 From imaginary experiments to quantum information
9/57
• Radioactivity has been around for 15 years.
1911Rutherford discovers
the nucleus
“use alpha particles tobombard gold atoms and
look at how they bounceback. Some come back
almost in the sametrajectory implying a verysmall but highly
concentrated group ofpositive charges.”
Ernest Rutherford
-
8/19/2019 From imaginary experiments to quantum information
10/57
1913 visit to Rutherford
Niels Bohr
-
8/19/2019 From imaginary experiments to quantum information
11/57
• 1920’s –Quantum Theory – Heisenberg
– Schrodinger
–
Dirac
– De Broglie
– Pauli
–
Born
-
8/19/2019 From imaginary experiments to quantum information
12/57
•
Quantum Theory
– Described by wavefunction
–
Describes probability, not “reality”. This is the source
of many discussions. –
Uncertainty principle – two properties (such asposition and velocity) cannot simultaneously beknown to arbitrary accuracy
–
Wave-particle duality – things can be wavelike orparticlelike
–
Principle of superposition
–
Wavefunction collapse when measured
-
8/19/2019 From imaginary experiments to quantum information
13/57
An electron is like a spinning top.
The spin can
only point up……or down
AND it can be BOTH up and down at
the same time!SUPERPOSTION:
" = 1
2
(# + $ )
-
8/19/2019 From imaginary experiments to quantum information
14/57
Fred Alan Wolf, "Taking the Quantum Leap"(Harper & Row, San Francisco, 1981)
How can something be “in two places at the same time”?
This “cube” could be
-
8/19/2019 From imaginary experiments to quantum information
15/57
or
Fred Alan Wolf, "Taking the Quantum Leap"(Harper & Row, San Francisco, 1981)
How can something be “in two places at the same time”?
this
-
8/19/2019 From imaginary experiments to quantum information
16/57
or
Fred Alan Wolf, "Taking the Quantum Leap"(Harper & Row, San Francisco, 1981)
How can something be “in two places at the same time”?
this
-
8/19/2019 From imaginary experiments to quantum information
17/57
and
Fred Alan Wolf, "Taking the Quantum Leap"(Harper & Row, San Francisco, 1981)
but
this this
No classical analog to superposition exists.
-
8/19/2019 From imaginary experiments to quantum information
18/57
• Quantum Mechanics
–
The most successful physical theory – Tested to parts in a trillion
– Never proven wrong or incomplete*
* Except it is not yet compatible with general relativity (gravity).
-
8/19/2019 From imaginary experiments to quantum information
19/57
• Quantum Mechanics enabled the Information
Age – The transistor (1948)
– Microelectronics
–
Lasers (1960) – Magnetic storage
-
8/19/2019 From imaginary experiments to quantum information
20/57
–
Quantum mechanics has given us a superb
understanding of chemistry and materials
-
8/19/2019 From imaginary experiments to quantum information
21/57
Einstein was not happy
with the consequences of
quantum mechanics
-
8/19/2019 From imaginary experiments to quantum information
22/57
Schroedinger reacted to
the questions of Einstein
with the termEntanglement.
This is where quantum
mechanics gets weird.
-
8/19/2019 From imaginary experiments to quantum information
23/57
If blue is measured V, red MUST be H
+
-
8/19/2019 From imaginary experiments to quantum information
24/57
David Wineland Nobel Lecture
-
8/19/2019 From imaginary experiments to quantum information
25/57
Correlations
-
8/19/2019 From imaginary experiments to quantum information
26/57
If blue is measured -45, red MUST be +45
+
-
8/19/2019 From imaginary experiments to quantum information
27/57
The dialogue between Bohr and Einstein was long
and many times included imaginary experiments
(gedanken) that quantum mechanics alwaysexplained
-
8/19/2019 From imaginary experiments to quantum information
28/57
Bohr drew thisimaginary experiment
to study the relation
between time andenergy with Einstein
-
8/19/2019 From imaginary experiments to quantum information
29/57
• 1964 John Bell:
– Is entanglement
measurable? – If we assume reality
and locality , this is not
consistent with the
results of QM
– tested numerous times
-
8/19/2019 From imaginary experiments to quantum information
30/57
• Bell theorem on 1964 implies that
You must give up something:
– Objective Reality
–
Locality (causality)
-
8/19/2019 From imaginary experiments to quantum information
31/57
• Quantum mechanics is a theory about
our (incomplete) knowledge of nature, not
of nature itself.
And that’s all there is.
-
8/19/2019 From imaginary experiments to quantum information
32/57
The end of Moore’s Law…
“In terms of size [of transistor] you can see that we are
approaching the size of atoms which is a fundamental
barrier…We have another 10 to 20 years ….” G. Moore
2009.
-
8/19/2019 From imaginary experiments to quantum information
33/57
Put weirdness of quantum mechanics to
work…
A second quantum revolution…
-
8/19/2019 From imaginary experiments to quantum information
34/57
David Wineland, Nobel Lecture
-
8/19/2019 From imaginary experiments to quantum information
35/57
Experiments manage to trap work individual matter quanta
starting in the 70s.
Trapped electrons and ions (Dehmelt and Wineland)Quantum jumps of electrons between levels in an ion
(Dehmelt, Toshek, Wineland)
Hans Dehmelt David Wineland
“Monoelectron Oscillator ” D Wineland P Ekstrom
-
8/19/2019 From imaginary experiments to quantum information
36/57
Monoelectron Oscillator, D. Wineland, P. Ekstrom,
and H. Dehmelt, Phys. Rev. Lett. 31, 2179 (1973)
-
8/19/2019 From imaginary experiments to quantum information
37/57
Experiments manage to trap and work with individual light
quanta starting in the 80s.
Trapped photons (Walther and Haroche)Micro-laser, Cavity Quantum Electrodynamics.
Serge HarocheHerbert Walther
-
8/19/2019 From imaginary experiments to quantum information
38/57
Quantum Mechanical formulation based on Quantum Jumps
(Zoller, Dalibard, Carmichael)
Peter Zoller Jean Dalibard Howard Carmichael
-
8/19/2019 From imaginary experiments to quantum information
39/57
“Observation of Quantum Jumps in a Single Ion,” J. C.
Bergquist, Randall G. Hulet, Wayne M. Itano, and D. J. Wineland
Phys. Rev. Lett. 57, 1699 (1986)
-
8/19/2019 From imaginary experiments to quantum information
40/57
Serge Haroche, Nobel Lecture
-
8/19/2019 From imaginary experiments to quantum information
41/57
Serge Haroche, Nobel lecture
-
8/19/2019 From imaginary experiments to quantum information
42/57
Two trapped ions (JQI Monroe Lab)
-
8/19/2019 From imaginary experiments to quantum information
43/57
Terraciano et al Nature Physics 2009
-
8/19/2019 From imaginary experiments to quantum information
44/57
Bennett
(1982)
Landauer
(1961)
Benioff
(1985)
Reversible computing (thermodynamics)
Deutsch
(1985)
Model of a universal quantum circuit
Feynman
(1982)
Quantum simulations
Quantum Information
-
8/19/2019 From imaginary experiments to quantum information
45/57
Quantum
MechanicsInformation
Science
Quantum Information Science
20th Century
21st Century
A New Science!
-
8/19/2019 From imaginary experiments to quantum information
46/57
Classical Bits vs Quantum Bits
Classical Bit: 0 or 1; or
Quantum Bit (Qubit):
Can be a quantum superposition of 0 and 1
# =
qubit +
-
8/19/2019 From imaginary experiments to quantum information
47/57
But entanglement, and the scaling that results, is the key
to the power of quantum computing.
Classically information is stored in a bit register: a 3-bit
register can store one number from 0 to 7
a | 000 + b | 001 + c | 010 + d | 011 $ + e | 100 + f | 101 + g | 110 + h | 111 $ • Result:
-- Classical: one N-bit number
-- Quantum: 2N (all possible) N-bit numbers
0 1
Quantum Mechanically, a register of 3 entangled
qubits can store all of these numbers in superposition:
1
-
8/19/2019 From imaginary experiments to quantum information
48/57
A hard problem-factoring large integers:
For example, it is hard to factor 167 659
But an elementary school student can easily multiply
389 x 431 = 167 659
-
8/19/2019 From imaginary experiments to quantum information
49/57
CRYPTOGRAPHY
Virtually all public key cryptographic systems
rely on the difficulty of factoring large numbers…
If you can figure out how to do this, your credit
card is not safe… and neither are governmentcommunications, financial transactions,personal information…
-
8/19/2019 From imaginary experiments to quantum information
50/57
12301866845301177551304949583849627207728535695
9
53347921973224521517264005072636575187452021997
8
64693899564749427740638459251925573263034537315
4
826850791702612214291346167042921431160222124047
9274737794080665351419597459856902143413
-
8/19/2019 From imaginary experiments to quantum information
51/57
12301866845301177551304949583849627207728535695
9
53347921973224521517264005072636575187452021997
8
64693899564749427740638459251925573263034537315
4
826850791702612214291346167042921431160222124047
9274737794080665351419597459856902143413
2 years 1000 computers
-
8/19/2019 From imaginary experiments to quantum information
52/57
12301866845301177551304949583849627207728535695953347921973224521517264005072636575187452021997864693899564749427740
6384592519255732630345373154826850791702612214291346167042
9214311602221240479274737794080665351419597459856902143413
1230186684530117755130494958384962720772853569595334792197
32245215172640050726365751874520219978646938995647494277406384592519255732630345373154826850791702612214291346167042
9214311602221240479274737794080665351419597459856902143413
4 years 1,000,000,000,000 computers
-
8/19/2019 From imaginary experiments to quantum information
53/57
The Quantum Computer
• 1994 Peter Shor
•
With Quantum Mechanics, it ispossible to factor an N-digitnumber in ~ N3 steps… muchfaster than the exponentially largenumber of steps that we neednow.
-
8/19/2019 From imaginary experiments to quantum information
54/57
Quantum computing:• Universial machine (Shor’s algorithm)
• Quantum simulation
Quantum cryptography:
• Key distribution (QKD)
• Secret sharing
Quantum Communication:
• Channel capacity
• Distributed computing
Quantum metrology
• Precision sensors
-
8/19/2019 From imaginary experiments to quantum information
55/57
A quantum computer (if we can make one) would be more
different from our current digital computers than our computers
are from the ancient abacus.
A general-purpose quantum computer is years away, but
along the way we will be exploring some of the most
important outstanding questions in science.
-
8/19/2019 From imaginary experiments to quantum information
56/57
Quantum Mechanics and Information Science have beentwo of the most important and revolutionary developments
in the XX Century, affecting both science and technology
Quantum mechanics changed the way we think about the
physical world and the nature of reality. It gave us modernelectronics with all its advantages.
Information science changed the way we think about
thinking. They gave us digital information.
They are now merging into Quantum information and we
can only wait a greater revolution.
-
8/19/2019 From imaginary experiments to quantum information
57/57
Thanks!