Creation operators and annihilation operators are mathematical operators that have widespread applications in quantum mechanics, notably in the study of quantum harmonic oscillators and many-particle systems. An annihilation operator (usually denoted ) lowers the number of particles in a given state by one. A creation operator (usually denoted ) increases the number of particles in a given state by one, and it is the adjoint of the annihilation operator. In many subfields of physics and chemistry, the use of these operators instead of wavefunctions is known as second quantization. They were introduced by Paul Dirac.
Creation and annihilation operators can act on states of various types of particles. For example, in quantum chemistry and many-body theory the creation and annihilation operators often act on electron states. They can also refer specifically to the ladder operators for the quantum harmonic oscillator. In the latter case, the raising operator is interpreted as a creation operator, adding a quantum of energy to the oscillator system (similarly for the lowering operator). They can be used to represent phonons. Constructing Hamiltonians using these operators has the advantage that the theory automatically satisfies the cluster decomposition theorem.
The mathematics for the creation and annihilation operators for bosons is the same as for the ladder operators of the quantum harmonic oscillator. For example, the commutator of the creation and annihilation operators that are associated with the same boson state equals one, while all other commutators vanish. However, for fermions the mathematics is different, involving anticommutators instead of commutators.
Quantum harmonic oscillator#Ladder operator method
In the context of the quantum harmonic oscillator, one reinterprets the ladder operators as creation and annihilation operators, adding or subtracting fixed quanta of energy to the oscillator system.
Creation/annihilation operators are different for bosons (integer spin) and fermions (half-integer spin).
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The goal of the course is to introduce relativistic quantum field theory as the conceptual and mathematical framework describing fundamental interactions such as Quantum Electrodynamics.
This lecture describes advanced concepts and applications of quantum optics. It emphasizes the connection with ongoing research, and with the fast growing field of quantum technologies. The topics cov
The goal of the course is to introduce relativistic quantum field theory as the conceptual and mathematical framework describing fundamental interactions.
Le 'spin' () est, en physique quantique, une des propriétés internes des particules, au même titre que la masse ou la charge électrique. Comme d'autres observables quantiques, sa mesure donne des valeurs discrètes et est soumise au principe d'incertitude. C'est la seule observable quantique qui ne présente pas d'équivalent classique, contrairement, par exemple, à la position, l'impulsion ou l'énergie d'une particule. Il est toutefois souvent assimilé au moment cinétique (cf de cet article, ou Précession de Thomas).
In quantum mechanics, a Fock state or number state is a quantum state that is an element of a Fock space with a well-defined number of particles (or quanta). These states are named after the Soviet physicist Vladimir Fock. Fock states play an important role in the second quantization formulation of quantum mechanics. The particle representation was first treated in detail by Paul Dirac for bosons and by Pascual Jordan and Eugene Wigner for fermions.
L'espace de Fock est une construction algébrique utilisée en mécanique quantique pour construire l'espace des états quantiques d'un nombre variable ou inconnu de particules identiques à partir d'une seule particule de l'espace de Hilbert H. Il porte le nom de Vladimir A. Fock qui l'a présenté pour la première fois dans son article de 1932 "Konfigurationsraum und zweite Quantelung", traduisible par "espace de configuration et deuxième quantification.
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