## Is the ground state a coherent state?

So the ground state of the system is a coherent state with parameter z=0.

### Why are coherent states important?

Coherent state can become a useful and important subject in physics because of its three unique properties: the coherence, the overcompleteness and the intrinsic geometrization. These unique properties, in certain contents, are fundamental to field theory.

**What is the time evolution of the coherent state?**

Further, in contrast to the energy eigenstates of the system, the time evolution of a coherent state is concentrated along the classical trajectories. The quantum linear harmonic oscillator, and hence coherent states, arise in the quantum theory of a wide range of physical systems.

**What are spin coherent states?**

Thus a spin coherent state is a quantum state that most closely resembles a semiclassical spin, in that 〈ˆS〉 is as large as possible and points in a particular direction. (Note, however, that ˆS|s〉≠s|s〉: a spin coherent state is not an eigenstate of the spin vector operator.)

## Are photons coherent?

Coherent light is a beam of photons (almost like particles of light waves) that have the same frequency and are all at the same frequency. In lasers, waves are identical and in phase, which produces a beam of coherent light.

### What is spin coherence?

The spin coherence of a pure state within the spin subspace for the particle is then defined as its coherent evolution under Hspm alone. The effect of interactions is to destroy this coherence.

**Why is ordinary light not coherent?**

Ordinary light is not coherent because it comes from independent atoms which emit on time scales of about 10^-8 seconds. There is a degree of coherence in sources like the mercury green line and some other useful spectral sources, but their coherence does not approach that of a laser.

**Why is light not coherent?**

Light emitted by normal means such as a flashlight or a bulb, is incoherent or the photons of the many wave frequencies of light are oscillating in different directions. Only a beam of laser light will not spread and diffuse. In lasers, waves are identical and in phase, which produces a beam of coherent light.

## What is the uncertainty in physics?

The uncertainty is the experimenter’s best estimate of how far an experimental quantity might be from the “true value.” (The art of estimating this uncertainty is what error analysis is all about).

### Which is the best description of a coherent state?

In physics, specifically in quantum mechanics, a coherent state is the specific quantum state of the quantum harmonic oscillator, often described as a state which has dynamics most closely resembling the oscillatory behavior of a classical harmonic oscillator.

**What makes a coherent state a specifc quantum state?**

A coherent state is a specifc kind of quantum state of the harmonic oscillator. Its wavefunction will satisfy the Heisenberg uncertainty principle with equality and the expectation values of position and momentum satisfy the classical equations of motion of a harmonic oscillator.

**What does the annihilation operator do to a coherent state?**

Physically, this formula means that a coherent state remains unchanged by the annihilation of field excitation or, say, a particle. An eigenstate of the annihilation operator has a Poissonian number distribution when expressed in a basis of energy eigenstates, as shown below.

## How is the coherent state related to classical solutions?

The coherent state describes a state in a system for which the ground-state wavepacket is displaced from the origin of the system. This state can be related to classical solutions by a particle oscillating with an amplitude equivalent to the displacement.