22.51
Quantum Theory of radiation interactions
Fall 2012 ~ Paola Cappellar o
1
Why QM?
Why study quantum theory of matter/radiation interactions?
1 ef fect of QM in natur e
1 application of QM in (almost) everyday life
your favorite QM application
2
Why QM?
Why study quantum theory of matter/radiation interactions?
1 ef fect of QM in natur e
Colors, photosynthesis, bir d compass ...
1 application of QM in (almost) everyday life
your favorite QM application
3
Why QM?
Why study quantum theory of matter/radiation interactions?
1 ef fect of QM in natur e
Colors, photosynthesis, bir d compass ...
1 application of QM in (almost) everyday life DVD (laser), GPS (atomic clock), MRI
your favorite QM application
4
Why QM?
Why study quantum theory of matter/radiation interactions?
1 ef fect of QM in natur e
Colors, photosynthesis, bir d compass ...
1 application of QM in (almost) everyday life DVD (laser), GPS (atomic clock), MRI
your favorite QM application
NMR (super conductivity + spins, simple to complex description)
5
Striking Characteristics of QM
Discr eteness
Ene r gy levels, quanta of light Discr ete systems
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Striking Characteristics of QM
Discr eteness
Ene r gy levels, quanta of light Discr ete systems
Interfer ence
Superposition states, entanglement
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Striking Characteristics of QM
Discr eteness
Ene r gy levels, quanta of light Discr ete systems
Interfer ence
Superposition states, entanglement Phase Coher ence
Disappearance of QM pr operties
8
Striking Characteristics of QM
Discr eteness
Ene r gy levels, quanta of light Discr ete systems
Interfer ence
Superposition states, entanglement Phase Coher ence
Disappearance of QM pr operties
These characteristics ar e r evealed in the interaction between matter and radiation
9
Y oung Double Slit experiment
A. T onomura, J. Endo, T . Matsuda, T . Kawasaki and H. Ezawa Am. J. of Phys. 57, 117 (1989)
Electr ons ar e emitted 1 b y 1 fr om the sour ce in the electr on micr oscope . The y pass thr ough a de vice called the "electr on biprism", which consists of tw o parallel plates and a fine filament at the cente r . Electr ons ar e then detected 1 b y 1 as par ticles at the detecto r . The electr ons w er e accelerated to about 40% of the speed of the light . So the y pass thr ough a 1m-long electr on micr oscope in 10 -8 s. Ther e is no mor e than one electr on in the micr oscope at one time , since onl y
10 electr ons ar e emitted per second. The exper i 1 m 0 ent lasts 20 min utes (video 1 min!)
Molecule interfe r ometry
M. Ar ndt, K. Hor nbe r ge r , A. Zeilinger
Images © source unknown. All rights reserved. This content is excluded from our Creative Commons license. For more information, see http://ocw.mit.edu/fairuse.
(a) The buckyball carbon-70 (and C-60) (1999)
(b) the pancak e-sha ped biomolecule tetra phen ylporph yrin (TPP) C 44 H 30 N 4 ; (2003)
(c) the fluorinated fuller ene C 60 F 48 . (2004)
TPP is the first-e v er biomolecule to sho w its wa v e natur e .
C 60 F 48 has an atomic mass of 1632 units and cur r entl y holds the w orld r ecor d f or the most massiv e and complex molecule to sho w interf er ence .
11
Sch r odinger ’ s virus
Quantum super position of living or ganisms. Illustr ation of the protocol to create quantum super position states applied to living or ganisms, such as vir uses, tr apped in a high-finesse optical ca vity b y optical
Courtesy of the Institute of Physics, available under a CC-BY license.
tw eez er s.
O . Romero-Isar t, M. L. Juan, R. Quidant and J. I. Cir ac , “ T o ward quantum super position of living or ganisms” New J. Ph ys. 12 033015 (2010)
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Cat State decohe r ence
© source unknown. All rights reserved. This content is excluded from our Creative Commons license. For more information, see http://ocw.mit.edu/fairuse .
R econstruction of non-classical ca vit y field states with snapshots of their decoherence
S. Deléglise,... & Se r ge Har oche, Natur e 455, 510 (2008)
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Quantum e.m. field in a cavity
Pr eparation of electr omagnetic radiation in Schrödinger cat states
Atoms cr ossing the cavity extract information about the field: r econstruction of state
Cavity damping induces decoher ence that quickly washes out interfer ences
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Experimental Setup
S’
g
B R 1
g e
S C
R 2
g e i n e
Measur e atoms
D
n = # of photons in cavity
Rydber g atoms ar e pr epar ed in the cir cular state |g> in box B.
The atoms cr oss the cavity C sandwiched between the Ramsey cavities R 1 and R 2 fed by the classical micr owave sour ce S’, befor e being detected in D.
The sour ce S pr epar es a coher ent field in C in the cat state.
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Schrödinger cat
Wigner Function r epr esentation
Cat = 12 photons (macr oscopic?)
Oscillation indicate entanglement (quantumness)
Reprinted by permission from Macmillan Publishers Ltd: Nature. Source: Deleglise, Samuel, et al. "Reconstruction of non-classical cavity field states with snapshots of their decoherence." Nature 455 © ( 2008 ): 510-4 .
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50 ms in the life of a Schrödinger cat
VIDEO
http://ww w .nature.com/nature/journal/v455/n7212/suppinfo/
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50 ms in the life of a Schrödinger cat
Reprinted by permission from Macmillan Publishers Ltd: Nature. Source: Deleglise, Samuel, et al. "Reconstruction of non-classical cavity field states with snapshots of their decoheren c 1 e 8 ." Nature 455, 510-514, © 2008.
Goals of Course
By the end of the term you should be able to Understand the concepts of moder n QM
entanglement,
open quantum system dynamics,
matter interaction with quantized e.m. field,...
19
Goals of Course
By the end of the term you should be able to Understand the concepts of moder n QM
entanglement,
open quantum system dynamics,
matter interaction with quantized e.m. field,...
Map experimental systems onto simplified models, describe them with the appr opriate mathematical tools
20
Goals of Course
By the end of the term you should be able to Understand the concepts of moder n QM
entanglement,
open quantum system dynamics,
matter interaction with quantized e.m. field,...
Map experimental systems onto simplified models, describe them with the appr opriate mathematical tools
Gr ow an appr eciation (inter est?) for contemporary topics of r esear ch in QM and its applications
21
Goals of Course
By the end of the term you should be able to Understand the concepts of moder n QM
entanglement,
open quantum system dynamics,
matter interaction with quantized e.m. field,...
Map experimental systems onto simplified models, describe them with the appr opriate mathematical tools
Gr ow an appr eciation (inter est?) for contemporary topics of r esear ch in QM and its applications
Stop worrying about the qualifying exam!
22
T extbooks
Lectur e notes
usually posted befor e the lectur e Recommended books
J.J. Sakurai Moder n Quantum Mechanics
M. Le Bellac Quantum Physics
Chen, S.H.; Kotlar chyk, M., Interactions of Photons and Neutr ons with Matter
Ballentine, Griffiths, Libof f, Har oche & Raimond, Scully & Zubairy
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P- Sets
The pr oblem sets ar e an essential part of the course: they ar e meant for you to lear n, not for me to judge you
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Grading
Homeworks will be graded on a 0-1 scale, 0 if no Pset, 1 for a serious ef fort.
The final grade will be
1
G = ( M E + F E ) h P s e t i + δ 2
Mid- T erm: October 29th
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22.51 Quantum Theory of Radiation Interactions
Fall 2012
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