Quantum Physics

Author: Michel Le Bellac; Patricia de Forcrand-Millard  

Publisher: Cambridge University Press‎

Publication year: 2011

E-ISBN: 9780511345562

P-ISBN(Paperback): 9781107602762

Subject: O413 quantum theory

Keyword: 量子论

Language: ENG

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Quantum Physics

Description

Quantum physics allows us to understand the nature of the physical phenomena which govern the behavior of solids, semi-conductors, lasers, atoms, nuclei, subnuclear particles and light. In Quantum Physics, Le Bellac provides a thoroughly modern approach to this fundamental theory. Throughout the book, Le Bellac teaches the fundamentals of quantum physics using an original approach which relies primarily on an algebraic treatment and on the systematic use of symmetry principles. In addition to the standard topics such as one-dimensional potentials, angular momentum and scattering theory, the reader is introduced to more recent developments at an early stage. These include a detailed account of entangled states and their applications, the optical Bloch equations, the theory of laser cooling and of magneto-optical traps, vacuum Rabi oscillations and an introduction to open quantum systems. This is a textbook for a modern course on quantum physics, written for advanced undergraduate and graduate students.

Chapter

1.6.8 Coherent and incoherent neutron scattering by a crystal

1.7 Further reading

2 The mathematics of quantum mechanics I: finite dimension

2.1 Hilbert spaces of finite dimension

2.2 Linear operators on H

2.2.1 Linear, Hermitian, unitary operators

2.2.2 Projection operators and Dirac notation

2.3 Spectral decomposition of Hermitian operators

2.3.1 Diagonalization of a Hermitian operator

2.3.2 Diagonalization of a 2×2 Hermitian matrix

2.3.3 Complete sets of compatible operators

2.3.4 Unitary operators and Hermitian operators

2.3.5 Operator-valued functions

2.4 Exercises

2.4.1 The scalar product and the norm

2.4.2 Commutators and traces

2.4.3 The determinant and the trace

2.4.4 A projector in R3

2.4.5 The projection theorem

2.4.6 Properties of projectors

2.4.7 The Gaussian integral

2.4.8 Commutators and a degenerate eigenvalue

2.4.9 Normal matrices

2.4.10 Positive matrices

2.4.11 Operator identities

2.4.12 A beam splitter

2.5 Further reading

3 Polarization: photons and spin-1/2 particles

3.1 The polarization of light and photon polarization

3.1.1 The polarization of an electromagnetic wave

3.1.2 The photon polarization

3.1.3 Quantum cryptography

3.2 Spin 1/2

3.2.1 Angular momentum and magnetic moment in classical physics

3.2.2 The Stern–Gerlach experiment and Stern–Gerlach filters

3.2.3 Spin states of arbitrary orientation

3.2.4 Rotation of spin 1/2

3.2.5 Dynamics and time evolution

3.3 Exercises

3.3.1 Decomposition and recombination of polarizations

3.3.2 Elliptical polarization

3.3.3 Rotation operator for the photon spin

3.3.4 Other solutions of (3.45)

3.3.5 Decomposition of a 2×2 matrix

3.3.6 Exponentials of Pauli matrices and rotation operators

3.3.7 The tensor Epsilonijk

3.3.8 A 2 rotation of spin 1/2

3.3.9 Neutron scattering by a crystal: spin-1/2 nuclei

3.4 Further reading

4 Postulates of quantum physics

4.1 State vectors and physical properties

4.1.1 The superposition principle

4.1.2 Physical properties and measurement

4.1.3 Heisenberg inequalities II

4.2 Time evolution

4.2.1 The evolution equation

4.2.2 The evolution operator

4.2.3 Stationary states

4.2.4 The temporal Heisenberg inequality

4.2.5 The Schrödinger and Heisenberg pictures

4.3 Approximations and modeling

4.4 Exercises

4.4.1 Dispersion and eigenvectors

4.4.2 The variational method

4.4.3 The Feynman–Hellmann theorem

4.4.4 Time evolution of a two-level system

4.4.5 Unstable states

4.4.6 The solar neutrino puzzle

4.4.7 The Schrödinger and Heisenberg pictures

4.4.8 The system of neutral K mesons

4.5 Further reading

5 Systems with a finite number of levels

5.1 Elementary quantum chemistry

5.1.1 The ethylene molecule

5.1.2 The benzene molecule

5.2 Nuclear magnetic resonance (NMR)

5.2.1 A spin 1/2 in a periodic magnetic field

5.2.2 Rabi oscillations

5.2.3 Principles of NMR and MRI

5.3 The ammonia molecule

5.3.1 The ammonia molecule as a two-level system

5.3.2 The molecule in an electric field: the ammonia maser

5.3.3 Off-resonance transitions

5.4 The two-level atom

5.5 Exercises

5.5.1 An orthonormal basis of eigenvectors

5.5.2 The electric dipole moment of formaldehyde

5.5.3 Butadiene

5.5.4 Eigenvectors of the Hamiltonian (5.47)

5.5.5 The hydrogen molecular ion H+2

5.5.6 The rotating-wave approximation in NMR

5.6 Further reading

6 Entangled states

6.1 The tensor product of two vector spaces

6.1.1 Definition and properties of the tensor product

Postulate V

6.1.2 A system of two spins 1/2

6.2 The state operator (or density operator)

6.2.1 Definition and properties

6.2.2 The state operator for a two-level system

6.2.3 The reduced state operator

6.2.4 Time dependence of the state operator

6.2.5 General form of the postulates

6.3 Examples

6.3.1 The EPR argument

6.3.2 Bell inequalities

6.3.3 Interference and entangled states

6.3.4 Three-particle entangled states (GHZ states)

6.4 Applications

6.4.1 Measurement and decoherence

6.4.2 Quantum information

6.5 Exercises

6.5.1 Independence of the tensor product from the choice of basis

6.5.2 The tensor product of two 2×2 matrices

6.5.3 Properties of state operators

6.5.4 Fine structure and the Zeeman effect in positronium

6.5.5 Spin waves and magnons

6.5.6 Spin echo and level splitting in NMR

6.5.7 Calculation of E(a, b)

6.5.8 Bell inequalities involving photons

6.5.9 Two-photon interference

6.5.10 Interference of emission times

6.5.11 The Deutsch algorithm

6.6 Further reading

7 Mathematics of quantum mechanics II: infinite dimension

7.1 Hilbert spaces

7.1.1 Definitions

7.1.2 Realizations of separable spaces of infinite dimension

7.2 Linear operators on H

7.2.1 The domain and norm of an operator

7.2.2 Hermitian conjugation

7.3 Spectral decomposition

7.3.1 Hermitian operators

7.3.2 Unitary operators

7.4 Exercises

7.4.1 Spaces of infinite dimension

7.4.2 Spectrum of a Hermitian operator

7.4.3 Canonical commutation relations

7.4.4 Dilatation operators and the conformal transformation

7.5 Further reading

8 Symmetries in quantum physics

8.1 Transformation of a state in a symmetry operation

8.1.1 Invariance of probabilities in a symmetry operation

8.1.2 The Wigner theorem

8.2 Infinitesimal generators

8.2.1 Definitions

8.2.2 Conservation laws

8.2.3 Commutation relations of infinitesimal generators

8.3 Canonical commutation relations

8.3.1 Dimension d = 1

8.3.2 Explicit realization and von Neumann’s theorem

8.3.3 The parity operator

8.4 Galilean invariance

8.4.1 The Hamiltonian in dimension d = 1

8.4.2 The Hamiltonian in dimension d = 3

8.5 Exercises

8.5.1 Rotations

8.5.2 Rotations and SU(2)

8.5.3 Commutation relations between momentum and angular momentum

8.5.4 The Lie algebra of a continuous group

8.5.5 The Thomas–Reiche–Kuhn sum rule

8.5.6 The center of mass and the reduced mass

8.5.7 The Galilean transformation

8.6 Further reading

9 Wave mechanics

9.1 Diagonalization of X and P and wave functions

9.1.1 Diagonalization of X

9.1.2 Realization in…

9.1.3 Realization in…

9.1.4 Evolution of a free wave packet

9.2 The Schrödinger equation

9.2.1 The Hamiltonian of the Schrödinger equation

9.2.2 The probability density and the probability current density

9.3 Solution of the time-independent Schrödinger equation

9.3.1 Generalities

9.3.2 Reflection and transmission by a potential step

The potential step: total reflection

The potential step: reflection and transmission

9.3.3 The bound states of the square well

9.4 Potential scattering

9.4.1 The transmission matrix

9.4.2 The tunnel effect

9.4.3 The S matrix

9.5 The periodic potential

9.5.1 The Bloch theorem

9.5.2 Energy bands

9.6 Wave mechanics in dimension d = 3

9.6.1 Generalities

9.6.2 The phase space and level density

9.6.3 The Fermi Golden Rule

9.7 Exercises

9.7.1 The Heisenberg inequalities

9.7.2 Wave-packet spreading

9.7.3 A Gaussian wave packet

9.7.4 Heuristic estimates using the Heisenberg inequality

9.7.5 The Lennard–Jones potential for helium

9.7.6 Reflection delay

9.7.7 A delta-function potential

9.7.8 Transmission by a well

9.7.9 Energy levels of an infinite cubic well in dimension d = 3

9.7.10 The probability current in three dimensions

9.7.11 The level density

9.7.12 The Fermi Golden Rule

9.7.13 Study of the Stern–Gerlach experiment

9.7.14 The von Neumann model of measurement

9.7.15 The Galilean transformation

9.8 Further reading

10 Angular momentum

10.1 Diagonalization of J2 and Jz

10.2 Rotation matrices

10.3 Orbital angular momentum

10.3.1 The orbital angular momentum operator

10.3.2 Properties of the spherical harmonics

1. Basis on the unit sphere

2. Relation to the Legendre polynomials

3. Transformation under rotation

4. Parity of the spherical harmonics

10.4 Particle in a central potential

10.4.1 The radial wave equation

10.4.2 The hydrogen atom

10.5 Angular distributions in decays

10.5.1 Rotations by pi, parity, and reflection with respect to a plane

10.5.2 Dipole transitions

10.5.3 Two-body decays: the general case

10.6 Addition of two angular momenta

10.6.1 Addition of two spins 1/2

10.6.2 The general case: addition of two angular momenta J1 and J2

10.6.3 Composition of rotation matrices

10.6.4 The Wigner–Eckart theorem (scalar and vector operators)

10.7 Exercises

10.7.1 Properties of J

10.7.2 Rotation of angular momentum

10.7.3 Rotations (theta, phi)

10.7.4 The angular momenta…

10.7.5 Orbital angular momentum

10.7.6 Relation between the rotation matrices and the spherical harmonics

10.7.7 Independence of the energy from m

10.7.8 The spherical well

10.7.9 The hydrogen atom for…

10.7.10 Matrix elements of a potential

10.7.11 The radial equation in dimension d = 2

10.7.12 Symmetry property of the matrices d(j)

10.7.13 Light scattering

10.7.14 Measurement of the Lambda0 magnetic moment

10.7.15 Production and decay of the rho+ meson

10.7.16 Interaction of two dipoles

10.7.17 Sigma0 decay

10.7.18 Irreducible tensor operators

10.8 Further reading

11 The harmonic oscillator

11.1 The simple harmonic oscillator

11.1.1 Creation and annihilation operators

11.1.2 Diagonalization of the Hamiltonian

11.1.3 Wave functions of the harmonic oscillator

11.2 Coherent states

11.3 Introduction to quantized fields

11.3.1 Sound waves and phonons

11.3.2 Quantization of a scalar field in one dimension

11.3.3 Quantization of the electromagnetic field

11.3.4 Quantum fluctuations of the electromagnetic field

11.4 Motion in a magnetic field

11.4.1 Local gauge invariance

11.4.2 A uniform magnetic field: Landau levels

11.5 Exercises

11.5.1 Matrix elements of Q and P

11.5.2 Mathematical properties

11.5.3 Coherent states

11.5.4 Coupling to a classical force

11.5.5 Squeezed states

11.5.6 Zero-point energy of the Debye model

11.5.7 The scalar and vector potentials in Coulomb gauge

11.5.8 Commutation relations and Hamiltonian of the electromagnetic field

11.5.9 Quantization in a cavity

11.5.10 Current conservation in the presence of a magnetic field

11.5.11 Non-Abelian gauge transformations

11.5.12 The Casimir effect

11.5.13 Quantum computing with trapped ions

11.6 Further reading

12 Elementary scattering theory

12.1 The cross section and scattering amplitude

12.1.1 The differential and total cross sections

12.1.2 The scattering amplitude

12.2 Partial waves and phase shifts

12.2.1 The partial-wave expansion

12.2.2 Low-energy scattering

12.2.3 The effective potential

12.2.4 Low-energy neutron–proton scattering

12.3 Inelastic scattering

12.3.1 The optical theorem

12.3.2 The optical potential

12.4 Formal aspects

12.4.1 The integral equation of scattering

12.4.2 Scattering of a wave packet

12.5 Exercises

12.5.1 The Gamow peak

12.5.2 Low-energy neutron scattering by a hydrogen molecule

12.5.3 Analytic properties of the neutron–proton scattering amplitude

12.5.4 The Born approximation

12.5.5 Neutron optics

12.5.6 The cross section for neutrino absorption

12.6 Further reading

13 Identical particles

13.1 Bosons and fermions

13.1.1 Symmetry or antisymmetry of the state vector

13.1.2 Spin and statistics

13.2 The scattering of identical particles

13.3 Collective states

13.4 Exercises

13.4.1 The Tonos- particle and color

13.4.2 Parity of the pi meson

13.4.3 Spin-1/2 fermions in an infinite well

13.4.4 Positronium decay

13.4.5 Quantum statistics and beam splitters

13.5 Further reading

14 Atomic physics

14.1 Approximation methods

14.1.1 Generalities

14.1.2 Nondegenerate perturbation theory

14.1.3 Degenerate perturbation theory

14.1.4 The variational method

14.2 One-electron atoms

14.2.1 Energy levels in the absence of spin

14.2.2 The fine structure

14.2.3 The Zeeman effect

14.2.4 The hyperfine structure

14.3 Atomic interactions with an electromagnetic field

14.3.1 The semiclassical theory

14.3.2 The dipole approximation

14.3.3 The photoelectric effect

14.3.4 The quantized electromagnetic field: spontaneous emission

14.4 Laser cooling and trapping of atoms

14.4.1 The optical Bloch equations

14.4.2 Dissipative forces and reactive forces

14.4.3 Doppler cooling

14.4.4 A magneto-optical trap

14.5 The two-electron atom

14.5.1 The ground state of the helium atom

14.5.2 The excited states of the helium atom

14.6 Exercises

14.6.1 Second-order perturbation theory and van der Waals forces

14.6.2 Order-alpha2 corrections to the energy levels

14.6.3 Muonic atoms

14.6.4 Rydberg atoms

14.6.5 The diamagnetic term

14.6.6 Vacuum Rabi oscillations

14.6.7 Reactive forces

14.6.8 Radiative capture of neutrons by hydrogen

14.7 Further reading

15 Open quantum systems

15.1 Generalized measurements

15.1.1 Schmidt’s decomposition

15.1.2 Positive operator-valued measures

15.1.3 Example: a POVM with spins 1/2

15.2 Superoperators

15.2.1 Kraus decomposition

15.2.2 The depolarizing channel

15.2.3 The phase-damping channel

15.2.4 The amplitude-damping channel

15.3 Master equations: the Lindblad form

15.3.1 The Markovian approximation

15.3.2 The Lindblad equation

15.3.3 Example: the damped harmonic oscillator

15.4 Coupling to a thermal bath of oscillators

15.4.1 Exact evolution equations

15.4.2 The Markovian approximation

15.4.3 Relaxation of a two-level system

15.4.4 Quantum Brownian motion

15.4.5 Decoherence and Schrödinger’s cats

15.5 Exercises

15.5.1 POVM as projective measurement in a direct sum

15.5.2 Using a POVM to distinguish between states

15.5.3 A POVM on two arbitrary qubit states

15.5.4 Transposition is not completely positive

15.5.5 Phase and amplitude damping

15.5.6 Details of the proof of the master equation

15.5.7 Superposition of coherent states

15.5.8 Dissipation in a two-level system

15.5.9 Simple models of relaxation

15.5.10 Another choice for the spectral function J(omega)

15.5.11 The Fokker–Planck–Kramers equation for a Brownian particle

15.6 Further reading

Appendix A The Wigner theorem and time reversal

A.1 Proof of the theorem

A.2 Time reversal

Appendix B Measurement and decoherence

B.1 An elementary model of measurement

B.2 Ramsey fringes

B.3 Interaction with a field inside the cavity

B.4 Decoherence

Appendix C The Wigner–Weisskopf method

References

Index

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