M EASUREMENT in

Q ua ntum M echanics

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YO U N G D O U B L E S L I T E X P E R I M E N T

Ref: A. To no mura, J. Endo , T. Matsuda, T. Kawasaki and H. Ezawa Am. J. o f P hy s. 5 7 , 1 1 7 (1 9 8 9 )

Electrons are emitted one b y one from the source in the electron microscope. They pass through a device called the "electron biprism", which consists of two par allel plates and a fine filament at the cente r . The filament is thinner than 1 micron (1/1000 mm) in diamete r . Electrons are then detected one b y one as particles at the detecto r .

The electrons were acceler ated to 50 k V , and therefore their speed is about 40% of the speed of the light (120,000 km/sec). So they pass through a one-meter -long electron microscope in 10 -8 s. There is no more than one electron in the microscope at one time, since only 10 electrons are emitted per second. The experiment lasts 20 minutes (video 1 min!)

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Compliments of the Central Research Laboratory, Hitachi, Ltd. Used with permission.

VIDEO

H I T AC H I R E S E A R C H L A B . H T T P : / / W W W . H I T AC H I . C O M / R D / R E S E A R C H / E M / DOUBLESLI T .HTML

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Ea ch e le ctr on position is r a n dom . . .

Compliments of the Central Research Laboratory, Hitachi, Ltd. Used with permission.

. . . b u t t h e p r o b a b i l i t y o f i t s p o s i t i o n i s

predicted b y the w a v efunction: P ( x ) = | ( x ) | 2 .

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Measuri ng the posi ti on of man y el ec t Z rons, w e

Compliments of the Central Research Laboratory, Hitachi, Ltd. Used with permission.

He r e , we d is c o v e r t h e p r o b a b ilit y

distribution of their positions

MOLECULE INTERFEROMET R Y

M. ARND T , K. HORNBERGER, A. ZEILINGER

(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 .

Courtesy of Markus Arndt. Used with permission.

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MIT OpenCourseWare http://ocw.mit.edu

22.02 Introduction to Applied Nuclear Physics

Spring 2012

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