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Introduction to Quantum Mechanics-II
Rating: 4.3 out of 5(2 ratings)
72 students

Introduction to Quantum Mechanics-II

An in-depth undergraduate course structured on the D.J. Griffiths's book
Last updated 3/2025
English

What you'll learn

  • Gain a strong understanding of foundational quantum principles and concepts.
  • Develop the ability to apply quantum mechanics to various physical systems and solve Schrödinger's equation.
  • Explore quantum mechanics in one dimension, focusing on particle-in-a-box problems and potentials.
  • Master quantum mechanics in three dimensions, including angular momentum, hydrogen atom, and central potentials.

Course content

2 sections46 lectures12h 35m total length
  • L1.1 Time independent non-degenerate perturbation theory23:11

    In this lecture, we dive into Time-Independent Perturbation Theory, a key concept in quantum mechanics. We will explore the fundamentals of perturbation theory, its applications, and how small disturbances or perturbations can affect quantum systems. Through examples such as the simple pendulum, we will demonstrate the role of small-amplitude approximations and how they lead to corrections in energy and wave functions. This lecture provides an in-depth understanding of how perturbations modify the behavior of quantum systems and is a crucial concept for advanced quantum mechanics students.

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  • L1.2 Time independent non-degenerate perturbation theory21:56

    In this quantum mechanics lecture, we delve into perturbation theory and its application to solving complex quantum systems. Starting with an overview of the time-independent Schrödinger equation, we explore zeroth, first, and second-order corrections to both the wave function and energy of quantum states. Special attention is given to the mathematical techniques involved in these corrections, including the use of Hermitian operators, orthonormal wave functions, and the Kronecker delta. The lecture also discusses the challenges of applying perturbation theory to real-world quantum systems and offers detailed solutions to common problems. This lecture is essential for anyone interested in advancing their understanding of quantum mechanics, specifically in perturbation theory, wave functions, and energy corrections.

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  • L2.1 Time independent non-degenerate perturbation theory22:06

    In this detailed lecture on Quantum Mechanics, we explore advanced topics related to perturbation theory and its application to quantum systems. Starting with an in-depth analysis of wave functions and their normalization, we progress to the calculation of energy corrections using first-order perturbation theory. The session also covers the first-order wave function correction, with a focus on applying the orthonormal set of wave functions for expanding the corrections. This tutorial is designed to aid students and researchers in understanding the mathematical framework behind quantum mechanics and provides step-by-step solutions to quantum perturbation problems.

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  • L2.2 Time independent non-degenerate perturbation theory21:56

    In this lecture on quantum mechanics, we dive deep into the perturbation theory and how it affects energy and wave functions in quantum systems. We begin by understanding the mathematical framework of perturbation, focusing on the first and second order corrections. Through detailed examples, we show how to calculate these corrections and interpret their significance in real-world quantum systems. We also cover the concept of indices and the role of the delta function in simplifying the correction calculations. This lecture is crucial for anyone studying quantum mechanics at an intermediate level, especially those interested in perturbation theory and its applications.

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  • L3.1 Time independent non-degenerate perturbation theory- Problems18:29

    In this quantum mechanics lecture, we delve into the concept of non-degenerate perturbation theory, covering its core principles, how to calculate the first and second order corrections to both energy and wave functions, and the distinction between degenerate and non-degenerate perturbations. Additionally, we solve problem 6.1, where we apply perturbation theory to an infinite square well with a delta potential, demonstrating the steps to calculate the energy and wave function corrections. This lecture is designed for students and enthusiasts of quantum mechanics, offering a clear understanding of perturbation theory applications.

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  • L3.2 Time independent non-degenerate perturbation theory- Problems16:52

    In this in-depth quantum mechanics lecture, we explore perturbation theory applied to the infinite square well model. Key topics include first-order energy corrections, modifications to wave functions, and the impact of the delta function. We provide a detailed walkthrough of the calculation steps for both odd and even energy levels and explain how to apply these corrections to quantum wave functions. This lecture is perfect for students and professionals seeking to understand advanced quantum mechanics concepts, including perturbation theory, wave function modifications, and quantum operators.

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  • L4.1 Time independent non-degenerate perturbation theory- Problems20:37

    In this quantum mechanics lecture, we tackle advanced perturbation theory in the context of quantum systems. Specifically, we focus on calculating the second-order energy corrections for a particle in a box scenario, using delta functions and applying quantum mechanical constraints on wavefunctions. Additionally, we delve into the interaction effects between identical bosons confined in an infinite square well, solving for ground state and first excited state wavefunctions both without and with perturbative interactions. This lecture is ideal for students looking to deepen their understanding of quantum perturbation theory, energy corrections, and the behavior of bosonic particles.

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  • L4.2 Time independent non-degenerate perturbation theory- Problems18:19

    This quantum mechanics lecture dives into the detailed calculations of first-order energy corrections using perturbation theory. Starting from a comprehensive explanation of integral simplifications, we go through key concepts like the delta function, integration over wavefunctions, and applying perturbations to both ground and excited states. You'll learn how to handle delta functions, substitution techniques, and approximations for energy corrections. This tutorial is perfect for students looking to strengthen their understanding of quantum mechanics and perturbation theory, especially in the context of the infinite square well model.

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  • L5.1 Degenerate perturbation theory18:13

    Dive deep into perturbation theory in quantum mechanics with this lecture! We begin by revisiting non-degenerate perturbation theory and explore energy and wave function corrections. Then, we tackle the challenges of degenerate states using the hydrogen atom as an example, explaining the need for time-independent degenerate perturbation theory. Key concepts like two-fold degeneracy, linear combinations of states, and energy corrections are discussed in detail. Perfect for students looking to strengthen their understanding of quantum systems and perturbation theory!

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  • L5.2 Degenerate perturbation theory18:50

    In this lecture on quantum mechanics, we explore advanced concepts of state representation and operator simplification. Key topics include deriving equations for quantum states, compact representations of operators, symmetry considerations, and conjugate properties of matrix elements. Step-by-step, we demonstrate how to simplify complex derivations, eliminate variables, and arrive at the final solution. This lecture is perfect for students aiming to deepen their understanding of quantum mechanics and mathematical formalism in physics.

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  • L5.3 Degenerate perturbation theory20:02

    In this lecture on quantum mechanics, we delve into the application of quadratic equations in determining energy eigenvalues. Learn how to simplify complex equations using the quadratic formula, understand the role of parameters like alpha and beta in wavefunctions, and explore conditions on coupling coefficients WAB. By the end of this session, you'll have a deeper understanding of eigenvalue derivations and their implications in quantum systems. Perfect for students and enthusiasts aiming to grasp advanced quantum mechanics concepts with practical algebraic insights.

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  • L6.1 Problem 6.6 Detailed Solution Part (a) 1/215:23

    Welcome to this detailed solution of Problem 6.6 from David J. Griffiths' Introduction to Quantum Mechanics (2nd Edition). In this video, we'll walk through the problem step by step, exploring the orthogonality of unperturbed states, matrix elements of the perturbation Hamiltonian, and energy shifts.

    Problem Statement:

    Let the two "good" unperturbed states be: ψ₀₊ = α₊ψₐ₀ + β₊ψ_b₀, where α₊ and β₊ are determined (up to normalization) by Equation 6.22 (or Equation 6.24).

    Show explicitly that:

    (a) ψ₀₊ and ψ₀₋ are orthogonal (⟨ψ₀₊|ψ₀₋⟩ = 0);

    (b) ⟨ψ₀₊|H'|ψ₀₋⟩ = 0;

    (c) ⟨ψ₀₊|H'|ψ₀₊⟩ = E₊¹ with E₊¹ given by Equation 6.27.


    This lecture dives into advanced quantum mechanics, focusing on degenerate perturbation theory and its applications. We explore fundamental equations, derive first-order energy corrections, and solve an intricate problem (6.6) that involves proving orthogonality of states and energy corrections under perturbation. Key topics include: Degenerate systems and their energy corrections Orthogonality and normalization of wave functions Applying quadratic formulas to derive corrections Real-world problem-solving to reinforce theoretical concepts Whether you're preparing for exams or looking to strengthen your grasp on quantum mechanics, this lecture offers detailed explanations and step-by-step problem-solving.

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  • L6.2 Problem 6.6 Detailed Solution Part (a) 2/215:35

    Welcome to this detailed solution of Problem 6.6 from David J. Griffiths' Introduction to Quantum Mechanics (2nd Edition). In this video, we'll walk through the problem step by step, exploring the orthogonality of unperturbed states, matrix elements of the perturbation Hamiltonian, and energy shifts.

    Problem Statement:

    Let the two "good" unperturbed states be: ψ₀₊ = α₊ψₐ₀ + β₊ψ_b₀, where α₊ and β₊ are determined (up to normalization) by Equation 6.22 (or Equation 6.24).

    Show explicitly that:

    (a) ψ₀₊ and ψ₀₋ are orthogonal (⟨ψ₀₊|ψ₀₋⟩ = 0);

    (b) ⟨ψ₀₊|H'|ψ₀₋⟩ = 0;

    (c) ⟨ψ₀₊|H'|ψ₀₊⟩ = E₊¹ with E₊¹ given by Equation 6.27.


    In this lecture on quantum mechanics, we delve into the intricacies of energy relations, focusing on E⁺ and E⁻ in matrix mechanics. We systematically derive key equations, simplify complex expressions, and explore the interplay of variables like Wab, Waa, and Wbb. Whether you're a student or an enthusiast, this lecture is designed to help you grasp the mathematical elegance of quantum mechanics. Stay tuned to master the algebraic techniques used in solving quantum equations and deepen your understanding of fundamental physics.

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  • L7.1 Problem 6.6 Detailed Solution Part (b) 1/216:19

    Welcome to this detailed solution of Problem 6.6 from David J. Griffiths' Introduction to Quantum Mechanics (2nd Edition). In this video, we'll walk through the problem step by step, exploring the orthogonality of unperturbed states, matrix elements of the perturbation Hamiltonian, and energy shifts.

    Problem Statement:

    Let the two "good" unperturbed states be: ψ₀₊ = α₊ψₐ₀ + β₊ψ_b₀, where α₊ and β₊ are determined (up to normalization) by Equation 6.22 (or Equation 6.24).

    Show explicitly that:

    (a) ψ₀₊ and ψ₀₋ are orthogonal (⟨ψ₀₊|ψ₀₋⟩ = 0);

    (b) ⟨ψ₀₊|H'|ψ₀₋⟩ = 0;

    (c) ⟨ψ₀₊|H'|ψ₀₊⟩ = E₊¹ with E₊¹ given by Equation 6.27.


    In this detailed lecture on quantum mechanics, we explore the fundamentals of perturbation theory and the mathematical techniques involved in simplifying complex wavefunction calculations. Key topics include proving orthogonality between Psi-plus-zero and Psi-minus-zero states, transforming terms using W_ij notation, and handling conjugates in equations. Step-by-step explanations and examples make this session ideal for advanced students aiming to master quantum mechanics concepts. Whether you're revising for exams or diving deeper into the nuances of perturbation theory, this lecture offers valuable insights and problem-solving strategies.

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  • L7.2 Problem 6.6 Detailed Solution Part (c) 2/211:43

    Welcome to this detailed solution of Problem 6.6 from David J. Griffiths' Introduction to Quantum Mechanics (2nd Edition). In this video, we'll walk through the problem step by step, exploring the orthogonality of unperturbed states, matrix elements of the perturbation Hamiltonian, and energy shifts.

    Problem Statement:

    Let the two "good" unperturbed states be: ψ₀₊ = α₊ψₐ₀ + β₊ψ_b₀, where α₊ and β₊ are determined (up to normalization) by Equation 6.22 (or Equation 6.24).

    Show explicitly that:

    (a) ψ₀₊ and ψ₀₋ are orthogonal (⟨ψ₀₊|ψ₀₋⟩ = 0);

    (b) ⟨ψ₀₊|H'|ψ₀₋⟩ = 0;

    (c) ⟨ψ₀₊|H'|ψ₀₊⟩ = E₊¹ with E₊¹ given by Equation 6.27.


    Dive into the detailed process of solving a quantum mechanics problem step by step! In this lecture, we focus on proving that the application of the Hamiltonian H′ on ψ±0 equals E±1. This includes expanding components, converting to matrix notations, and performing critical cancellations. By the end, we demonstrate the role of normalization in completing the proof. Perfect for undergraduate students and those exploring advanced problem-solving in quantum mechanics.

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  • L8.1 Example 6.2 Degenerate Perturbation Theory 1/716:45

    In this lecture on quantum mechanics, we dive into Example 6.2 from Griffiths' second edition, exploring the three-dimensional infinite cubical well. The lecture begins with a detailed explanation of the potential inside and outside the well and proceeds to derive the wave functions and energy levels for both the ground and first excited states. Key concepts like degeneracy, stationary states, and triply degenerate states are thoroughly discussed, with mathematical derivations and intuitive analogies to aid understanding. Whether you're revising for exams or looking to strengthen your grasp of quantum mechanics, this lecture provides a comprehensive breakdown of the topic.

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  • L8.2 Example 6.2 Degenerate Perturbation Theory 2/716:12

    Dive into this detailed lecture on quantum mechanics as we explore first-order corrections to the ground state energy using perturbation theory. Learn to derive and simplify the wave function, set up integrals for energy corrections, and use symmetry and standard integral relationships for precise calculations. This session is a must-watch for students and enthusiasts looking to master advanced quantum mechanics concepts. Don't miss out on practical tips and techniques to enhance your understanding of quantum systems!

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  • L9.1 Example 6.2 Degenerate Perturbation Theory 3/713:29

    In this lecture, we delve into the quantum mechanics of first-order energy corrections for the first excited state of a particle. Learn to apply degenerate perturbation theory for triply degenerate energy levels and solve complex 3x3 matrices using symmetry properties of wave functions. Through step-by-step derivations, we evaluate integral expressions for wave functions and explore how quantum states like contribute to the energy corrections. This session is ideal for students seeking a clear understanding of perturbation theory in quantum mechanics.

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  • L9.2 Example 6.2 Degenerate Perturbation Theory 4/714:33

    In this in-depth lecture on Quantum Mechanics, we explore the calculation of quantum matrix elements and symmetric integrals. Starting with an introduction to key concepts like Psi functions and sine integrals, we work through advanced formulas and calculations used to evaluate diagonal elements and their interactions in quantum systems. This lecture also includes practical examples where we calculate integral terms step by step. Whether you're a beginner or looking to deepen your understanding of quantum state integrals, this lecture will guide you through key principles and practical techniques for solving complex quantum mechanical problems.

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  • L10.1 Example 6.2 Degenerate Perturbation Theory 5/712:44

    This lecture dives deep into advanced quantum mechanics concepts, focusing on integration techniques, symmetry effects, and their application in calculating quantum variables and matrix elements. Learn the steps for solving quantum mechanical integrals, applying limits, and deriving key results. The lecture also covers the significance of symmetry in these calculations and how it helps simplify complex quantum systems. This tutorial is ideal for advanced students looking to understand quantum integrals and their role in constructing quantum matrices.

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  • L10.2 Example 6.2 Degenerate Perturbation Theory 6/715:32

    In this quantum mechanics lecture, we delve into the application of matrix mechanics, exploring how to calculate and manipulate matrix elements in the context of perturbation theory. We will discuss the construction and simplification of the W matrix, find the characteristic equation, and explore the determinant's role in solving the system. We then apply perturbation theory to split the energy levels of a degenerate state into three distinct energies. Through this example, we illustrate key principles of quantum mechanics, including matrix operations, characteristic equations, and degenerate perturbation theory. Perfect for those looking to understand the intricacies of quantum systems and the mathematical tools used to analyze them.

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  • L11.1 Example 6.2 Degenerate Perturbation Theory 7/715:30

    In this lecture, we explore the concept of degenerate states in quantum mechanics and how perturbation theory is used to split them into non-degenerate states. Through linear combinations of wave functions, we calculate the eigenvalues and eigenvectors for a system and apply degenerate perturbation theory to determine the resulting states. By analyzing the coefficients and energy levels, we gain a deeper understanding of how perturbations affect the quantum states, including the calculation of eigenvectors and the normalization process. This lecture also covers the application of non-degenerate perturbation theory for correcting energy levels and obtaining the correct results.

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  • L11.2 Solution Problem 6.8 Degenerate Perturbation Theory 1/318:31

    Problem 6.8

    In this problem, we perturb the infinite cubical well (discussed in Problem 4.2) by introducing a delta function "bump" at the point (a/4, a/2, 3a/4):

    H' = a^3 * V0 * δ(x - a/4) * δ(y - a/2) * δ(z - 3a/4)

    where V0 is a constant with units of energy.

    (a) Find the first-order correction to the energy of the ground state.

    (b) Are any of the excited states degenerate?

    If so, use degenerate perturbation theory to calculate their first-order corrections to the energies.

    In this quantum mechanics lecture, we solve a perturbation theory problem involving an infinite cubical well. The problem introduces a delta function perturbation at specific points within the well and requires the calculation of first-order energy corrections for both the ground state and triply degenerate first excited state. Throughout the lecture, we apply key principles of perturbation theory, including the evaluation of wave functions and delta function integrals. This tutorial covers step-by-step solutions and demonstrates the process of calculating energy corrections using perturbation theory in quantum mechanics. Ideal for students studying perturbation theory and energy corrections in quantum systems.

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  • L12.1 Solution Problem 6.8 Degenerate Perturbation Theory 2/318:29

    Problem 6.8

    In this problem, we perturb the infinite cubical well (discussed in Problem 4.2) by introducing a delta function "bump" at the point (a/4, a/2, 3a/4):

    H' = a^3 * V0 * δ(x - a/4) * δ(y - a/2) * δ(z - 3a/4)

    where V0 is a constant with units of energy.

    (a) Find the first-order correction to the energy of the ground state.

    (b) Are any of the excited states degenerate?

    If so, use degenerate perturbation theory to calculate their first-order corrections to the energies.

    In this in-depth quantum mechanics lecture, we explore the intricate details of wave function calculations, specifically focusing on integrals involving sine functions and delta functions. We discuss the physical meaning of these integrals and their implications for quantum systems. The lecture covers both diagonal and off-diagonal elements in wave function matrices, providing clarity on the underlying quantum mechanics principles. Key concepts like orthonormality and wave function normalization are emphasized, and the lecture includes step-by-step solutions to quantum integrals and their simplification. This lecture is perfect for students seeking to deepen their understanding of wave function analysis in quantum mechanics.

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  • L12.2 Solution Problem 6.8 Degenerate Perturbation Theory 3/38:30

    Problem 6.8

    In this problem, we perturb the infinite cubical well (discussed in Problem 4.2) by introducing a delta function "bump" at the point (a/4, a/2, 3a/4):

    H' = a^3 * V0 * δ(x - a/4) * δ(y - a/2) * δ(z - 3a/4)

    where V0 is a constant with units of energy.

    (a) Find the first-order correction to the energy of the ground state.

    (b) Are any of the excited states degenerate?

    If so, use degenerate perturbation theory to calculate their first-order corrections to the energies.

    In this comprehensive lecture on quantum mechanics, we dive deep into matrix elements and the characteristic equation for a system. The discussion includes detailed steps in calculating eigenvalues and their significance, along with the first-order energy corrections for degenerate states. We'll also touch on advanced topics such as the fine structure of the hydrogen atom, the Zeeman effect, and relativistic corrections. This lecture provides a detailed breakdown of these crucial concepts and how they are handled within quantum mechanics. Perfect for students looking to grasp the complexities of quantum mechanics.

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Requirements

  • Prior to embarking on this course, it is recommended to have a foundational understanding of Quantum Mechanics-I.

Description

This internationally renowned course, "Introduction to Quantum Mechanics" by David J. Griffiths, is designed to provide undergraduate students with a comprehensive introduction to the fascinating and foundational realm of quantum physics. Taught at universities around the world, this course caters to Bachelor of Science (BS) students, equipping them with the fundamental principles, concepts, and mathematical tools required to explore the intriguing and often counterintuitive world of quantum mechanics.

Throughout the course, students will delve into the principles of wave-particle duality, superposition, and quantum states, learning to navigate the behavior of particles at the atomic and subatomic levels. The course covers topics such as the Schrödinger equation, quantum operators, angular momentum, and the quantum mechanics of systems with spin. Moreover, students will gain insights into the quantum mechanics of systems including the hydrogen atom, and simple harmonic oscillators.

David J. Griffiths, a renowned physicist and author of widely used textbooks in the field, brings his expertise to bear on this course. He guides students through both the conceptual foundations and practical applications of quantum mechanics, fostering a deep understanding of this crucial area of physics. By the end of this course, students will have a solid grounding in quantum mechanics, providing a springboard for further studies in physics or related fields, as well as a profound appreciation for the quantum mysteries that underpin our physical world.

Who this course is for:

  • This course is designed for students and enthusiasts of physics, aspiring physicists, engineers, or anyone with an interest in understanding the fundamental principles and applications of quantum mechanics as outlined in David J. Griffiths' introductory book.