Lect. 1: Introduction

Transcription

1 Lecturer: Prof. Woo-Young Choi ( 최우영 ) Room: B625, Tel: wchoi@yonsei.ac.kr, Web: tera.yonsei.ac.kr Why study Quantum Mechanics?... Dass ich erkenne, was die Welt Im Innersten zusammenhält... (Goethe, Faust) That I may understand whatever binds the world s innermost core together Goals - Understand basics of QM - Learn certain applications of QM for EEE including quantum information Prerequisites - Curiosity - Basic understanding of waves (E&M waves) - Basic understanding of linear algebra

2 Topics (Tentative and subject to changes) 1. Toward quantum mechanics 2. Schroedinger wave equation 3. Time-dependent Schroedinger wave equation 4. Eigen states and operators 5. Quantum information

3 Textbooks

4 Grades - 2 x 35 points (1st test: Oct. 15 during the class) - Review presentation in English: 20 points - Attendance and class participation: 10 points

5 19th century - Collapse of Spanish, French (Napoleon), Chinese - Growing influence of British, German, Russian Empires, and US - For example, British Empire - Industrial Revolution ( ) - Queen Victoria ( ) - Almost ¼ of the entire world population The most powerful country in entire human history!

6 19th century scientists Michael Faraday ( ) James Clerk Maxwell ( ) Heinrich Hertz ( ) Understanding of E&M

7 19th century scientists William Hamilton ( ) Ludwig Boltzmann ( ) William Thomson (aka Lord Kelvin) ( ) Hamiltonian Mechanics Statistical Mechanics Thermodynamics Understanding of classical mechanics and thermodynamics

8 19th century technologiests George Stephenson ( ) First railway line using steam locomotives Gottlieb Daimler ( ) High-speed petrol engine Alexander Graham Bell ( ) First practical telephone

9 In 19th century, - Many especially in European countries economically very affluent, (Colonies, new technologies) - Scientists full of optimism (Many new discoveries and fairly good understanding of these) Very willing to try various new experimental and theoretical approaches

10 But a puzzling experimental result: Blackbody radiation Rayleigh-Jeans Law: 8 3 c kt Planck suggested in 1901 that vibrating atoms only radiate or absorb energy in discrete packets E n = n h Fitted the measurement well with h = 6.63 x J sec Planck Law approaches R-J Law when hν<<kt.

11 Another puzzling experimental result: Photoelectron effects - Amount of emitted electrons depends on light intensity - Same minimum voltage for current flow regardless of light intensity Same max. kinetic energy for emitted electrons regardless of light intensity? What determines the max. kinetic energy of emitted electrons?

12 (Max. kinetic energy of emitted electrons) -No electron emission if is smaller than a certain value -K max increases with These cannot be explained by wave nature of light. Larger intensity => larger E-field But larger E-field inserts larger force (F=qE) and therefore photoelectronics should have larger kinetic energy Einstein s explanation: Light delivers energy in chunks (photons)! (1905) Ephoton h

13 Furthermore If light has particle property, other particle-like matters have wave property De Broglie s hypothesis (1924) For matter waves, = h/p

14 Double-slit experiment (Dr. Quantum Double Slit Experiment in Youtube) - For any waves, well-known phenomenon - For particles such as electroncs? (Dr. Quantum Double Slit Experiment in Youtube)