To prove that a coherent state is an eigenstate of the annihilation operator

In summary, a coherent state is a quantum state of a harmonic oscillator that exhibits properties of both a particle and a wave, and is related to the annihilation operator, which is a mathematical operator that lowers the energy of the system by one unit. The proof that a coherent state is an eigenstate of the annihilation operator is significant in understanding the behavior of a harmonic oscillator in quantum mechanics and has practical applications in fields such as quantum optics and quantum information processing. The proof involves using the commutation relation between the annihilation and creation operators, along with the properties of a coherent state, to show that the annihilation operator returns the coherent state multiplied by a complex number. This is done through various mathematical techniques, such as using ladder operators and
  • #1
chmodfree
7
3
Moved from a technical forum, so homework template missing.
The definition of coherent state $$|\phi\rangle =exp(\sum_{i}\phi_i \hat{a}^\dagger_i)|0\rangle $$
How can I show that the state is eigenstate of annihilation operator a?
i.e.
$$\hat{a}_i|\phi\rangle=\phi_i|\phi\rangle$$
 
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  • #2
chmodfree said:
How can I show that the state is eigenstate of annihilation operator a?

What does the annihilation operator do to each term in the sum?
 
  • #3
PeterDonis said:
What does the annihilation operator do to each term in the sum?
Maybe one should add that the exponential function must be expanded in the Taylor series.
 

1. What is a coherent state?

A coherent state is a quantum state that exhibits classical-like properties, such as a well-defined position and momentum. It is a superposition of different energy levels and is described by a wave function that is a Gaussian distribution in both position and momentum space.

2. What is an eigenstate of the annihilation operator?

An eigenstate of the annihilation operator is a state in which the annihilation operator acts as a scalar multiple of the state. In other words, the state is unchanged when the annihilation operator is applied to it.

3. How can a coherent state be proven to be an eigenstate of the annihilation operator?

A coherent state can be proven to be an eigenstate of the annihilation operator by showing that the annihilation operator acting on the coherent state results in the same coherent state multiplied by a complex number, known as the eigenvalue.

4. What is the significance of proving that a coherent state is an eigenstate of the annihilation operator?

Proving that a coherent state is an eigenstate of the annihilation operator confirms that the coherent state is a stable and well-defined quantum state. It also allows for the calculation of the average number of particles in the coherent state, which is equal to the eigenvalue of the annihilation operator.

5. How does this proof relate to the broader field of quantum mechanics?

This proof is an important demonstration of the principles of quantum mechanics, specifically the concept of eigenstates and operators. It also has practical applications in fields such as quantum computing and quantum information processing.

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