Lect. 1: Introduction - Yonsei Universitytera.yonsei.ac.kr/class/2014_2_2/lecture/Lect 1 Introduction.pdf · Quantum Mechanics (14/2) W.-Y. Choi Lect. 1: Introduction 19th century

Quantum Mechanics (14/2) W.-Y. Choi

Lect. 1: Introduction

● Why study Quantum Mechanics?

● Lecturer: Prof. Woo-Young Choi (최우영) Room: B625, Tel: 02-2123-2874 Email: [email protected], Web: tera.yonsei.ac.kr

● Prerequisites- Curiosity - Basic understanding of ‘waves’ (E&M waves)

- Basic understanding of linear algebra

● Goals

- Understand basics of QM - Learn certain applications of QM for EEE including quantum information

... Dass ich erkenne, was die Welt Im Innersten zusammenhält ... (Goethe, Faust)

… That I may understand whatever binds the world’s innermost core together …

Quantum Mechanics (14/2) W.-Y. Choi

Lect. 1: Introduction

● 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

Quantum Mechanics (14/2) W.-Y. Choi

Lect. 1: Introduction

● Textbooks

http://iffwww.iff.kfajuelich.de/~ekoch/QM10

Quantum Mechanics (14/2) W.-Y. Choi

Lect. 1: Introduction

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

Quantum Mechanics (14/2) W.-Y. Choi

Lect. 1: Introduction

● 19th century

- Industrial Revolution (1760 – 1840)

- Collapse of Spanish, French (Napoleon), Chinese

- For example, British Empire

- Queen Victoria (1819 – 1901)

- Almost ¼ of the entire world population

The most powerful country in entire human history!

- Growing influence of British, German, Russian Empires, and US

Quantum Mechanics (14/2) W.-Y. Choi

Lect. 1: Introduction

● 19th century scientists

Michael Faraday (1791-1867)

Heinrich Hertz (1857 – 1894)

James Clerk Maxwell(1831-1879)

Understanding of E&M

Quantum Mechanics (14/2) W.-Y. Choi

Lect. 1: Introduction

● 19th century scientists

William Hamilton(1805-1865)

Hamiltonian Mechanics

Ludwig Boltzmann (1844 – 1906)

Statistical Mechanics

William Thomson (aka Lord Kelvin)

(1844 – 1906)

Thermodynamics Understanding of classical mechanics and thermodynamics

Quantum Mechanics (14/2) W.-Y. Choi

Lect. 1: Introduction

● 19th century technologiests

George Stephenson(1781-1848)

First railway line using steam locomotives

Alexander Graham Bell(1847-1922)

First practical telephone

Gottlieb Daimler (1834-1900)

High-speed petrol engine

Quantum Mechanics (14/2) W.-Y. Choi

Lect. 1: Introduction

● 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

Quantum Mechanics (14/2) W.-Y. Choi

Lect. 1: Introduction

● But a puzzling experimental result: Blackbody radiation

Rayleigh-Jeans Law:3

8 kTc

Planck Law approaches R-J Lawwhen hν<<kT.

Planck suggested in 1901 that vibrating atoms only radiate or absorb energy in discrete packetsEn = n h

Fitted the measurement well withh = 6.63 x 10-34 J sec

Quantum Mechanics (14/2) W.-Y. Choi

Lect. 1: Introduction

● 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?

Quantum Mechanics (14/2) W.-Y. Choi

Lect. 1: Introduction

(Max. kinetic energy of emitted electrons)

These cannot be explained by wave nature of light.

Larger intensity => larger E-fieldBut larger E-field inserts larger force (F=qE) and therefore photoelectronics should have larger kinetic energy

- No electron emission if is smaller than a certain value- Kmax increases with

photonE hEinstein’s explanation: Light delivers energy in chunks (photons)! (1905)

Quantum Mechanics (14/2) W.-Y. Choi

Lect. 1: Introduction

● Furthermore …

If light has particle property, other particle-like matters have wave property

● De Broglie’s hypothesis (1924)

For matter waves, = h/p

Quantum Mechanics (14/2) W.-Y. Choi

Lect. 1: Introduction

● 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)