Lesson 1: Introduction - Yonsei Universitytera.yonsei.ac.kr/class/2016_2_2/lecture/Lesson 1 Introduction.pdf · Quantum Mechanics (16/2) W.-Y. Choi Lesson 1: Introduction Flipped

Quantum Mechanics (16/2) W.-Y. Choi

Lesson 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 (quantum information)

... Dass ich erkenne, was die Welt Im Innersten zusammenhält ...

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

(Goethe, Faust)



● 19th century

- Industrial Revolution (1760 – 1840)

- Collapse/Dewindling of Spanish, French (Napoleon), Chinese Empires

- For example, British Empire

- Queen Victoria (1819 – 1901)

- Almost ¼ of the entire world population

Probably the most powerful country in entire human history!

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



● 19th Century Scientists

Michael Faraday (1791-1867)

Heinrich Hertz (1857 – 1894)

James Clerk Maxwell(1831-1879)

Understanding of E&M



● 19th Century Scientists

William Hamilton(1805-1865)

Ludwig Boltzmann (1844 – 1906)

William Thomson (aka Lord Kelvin)

(1824 – 1907)

Understanding of classical mechanics and thermodynamics

Statistical Mechanics ThermodynamicsHamiltonian Mechanics



● 19th Century Technologiests

George Stephenson(1781-1848)

Alexander Graham Bell(1847-1922)

Gottlieb Daimler (1834-1900)

First railway line using steam locomotives High-speed petrol engine First practical telephone



● In 19th century,

- Many especially European countries were economically very affluent(Colonies, new technologies)

- Scientists were full of optimism (Many new discoveries and fairly good understanding of these)

Very willing to try various new experimental and theoretical approaches



● Blackbody radiation

Rayleigh-Jeans Law:3

8 kTc

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

Planck suggested in 1900 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

Gustav Kirchhoff(1824-1887)



● But a puzzling experimental result: Blackbody radiation

Rayleigh-Jeans Law:3

8 kTc

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

Planck suggested in 1900 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

Max Planck (1858~1947)Nobel in 1918



● 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?



(Max. kinetic energy of emitted electrons)

These could not 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)

Einstein (1879~1955)Nobel in 1921



● Hydrogen atom emission spectra

quantized angular momentum

L = n h/2

Niels Bohr(1885-1962)

Nobel in 1922



● Furthermore …

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

De Broglie’s hypothesis (1924)

For matter waves, = h/pLouis De Broglie

(1892-1987)Nobel in 1929

● Double-slit experiment



● Pioneers of Quantum Mechanics

Erwin Schrödinger(1887-1961)

Nobel in 1933

Werner Heisenberg(1901-1976)

Nobel in 1932

Niels Bohr(1885-1962)

Nobel in 1922

Max Born(1882-1970)

Nobel in 1954



● What is Quantum Mechanics good for ?



● Topics (Tentative and subject to changes)

- Lesson 1: Introduction- Lesson 2: Review of classical mechanics- Lesson 3: Plane waves, interference, diffraction- Lesson 4: Schrödinger's equation- Lesson 5: Particle in a box- Lesson 6: Particles and barriers- Lesson 7: Particles in potential wells- Lesson 8: Time-dependent Schrödinger's equation- Lesson 9: Time evolution of superpositions- Lesson 10: Group velocity, dispersion- Lesson 11: Measurement- Lesson 12: Uncertainty principle and particle current- Lesson 13: Functions and Dirac Notation- Lesson 14: Vector space, operators and matrices- Lesson 15: Identity operator

- Lesson 16: Unitary and Hermitian operator- Lesson 17: Hermitian operator in quantum mechanics- Lesson 18: Angular momentum- Lesson 19: The L squared operator- Lesson 20: Hydrogen atom- Lesson 21: The hydrogen atom solutions- Lesson 22: Approximation methods- Lesson 23: Perturbation theory- Lesson 24: Tight bonding model- Lesson 25: Time-dependent perturbation- Lesson 26: Fermi's golden rule- Lesson 27: Quantum information



● Textbooks ● Youtube:



● Flipped Learning

- Students watch Youtube lectures BEFORE the class! - Discussion, Q&A, evaluation during the class

- Lesson 1: Introduction (1a-d, e-j optional,9/7)- Lesson 2: Review of classical mechanics (2a-d, 9/12)- Lesson 3: Plane waves, interference, diffraction (3a-c, 9/19)- Lesson 4: Schrödinger's equation (4a-d, 9/21)- Lesson 5: Particle in a box (5a-d, 9/26)- Lesson 6: Particles and barriers (6a-c, 9/28)- Lesson 7: Particles in potential wells (7a-c, 10/5)- Lesson 8: Time-dependent Schrödinger's equation (8a-c, 10/10)- Lesson 9: Time evolution of superpositions (9a-d, 10/12)

Mid-term Examination (10/17)

● Schedule (Tentative)



- Lesson 10: Wave packet (10a-d, e-j optional,10/24)- Lesson 11: Measurement and expectation value (11a-c, 10/26)- Lesson 12: Uncertainty priciple and particle current (12a-b, 10/31)- Lesson 13: Functions and Dirac notation (13a-d, 11/2)- Lesson 14: Vector space, operators and matrices (14a-c, 11/7)- Lesson 15: Identify operator (15a-c, 11/9)- Lesson 16: Unitary and Hermitian operator (16a-c, 11/14)- Lesson 17: Hermitian operator in quantum mechanics (17a-c, 11/16)- Lesson 18: Angular momentum (18a-b, 11/21)- Lesson 19: The L squared operator (19a-c, 11/23)- Lesson 20: Hydrogen atom (20a-c,11/28)- Lesson 21: The hydrogen atom solutions (21a-b,11/30)- Lesson 22: Quantum informaton 1 (John Preskill, Introduction to Quantum Informatoin, Part 1, 12/5)

- Lesson 23: Quantum informaton 2(John Preskill, Introduction to Quantum Informatoin, Part 2, 12/7)

- Student Presentation (12/12)

Final Examination (12/14)

● Schedule (Tentative)



● Class HoursMon. 11:00-12:00 am, Wed. 2:00-4:00 pm Mon. 11:00-12:30 am, Wed. 2:30-4:00 pm

- Summary Presentation by one student in English starting next week- Q/A and discussions- Quiz

● Grades- Tests: 2 x 25 points - Quizzes: 20 points - Review presentation in English: 20 points - Attendance and class participation: 10 points



Every student has a chance to make English presentation in this class.He/she should study the topic he/she signed up for by watching theYoutube lesson, summarizes it in a ppt file, and make a presentationin English during the class. The presentation should be about 15 mins.and it will be evaluated based on following:

- How well the student understands the lesson materials.- How well the student summarizes the lesson materials.- How well the student make the presentation in the class.

Summary Presentation in English



- Lesson 2 (9/12) 김민규- Lesson 3 (9/19) 배민수- Lesson 4 (9/21) 박진관- Lesson 5 (9/26) 박천택- Lesson 6 (9/28) 인치훈- Lesson 7 (10/5) 김상 인- Lesson 8 (10/10) 정문강- Lesson 9 (10/12) 김범- Lesson 10 (10/24) 이동현

Quantum MechanicsSummary Presentation in English

Documents

Lesson 1: Introduction - Yonsei Universitytera.yonsei.ac.kr/class/2016_2_2/lecture/Lesson 1 Introduction.pdf · Quantum Mechanics (16/2) W.-Y. Choi Lesson 1: Introduction Flipped