Definitions

Question 1

Difference between photons and atoms?

Answer 1

Coherent light can be produced by lasers for photons while coherent beams of atoms can be produced by Bose-Einstein condensates

Question 2

What is the temperate dependence for the de Broglie wavelength?

Answer 2

As the temperature decreases the de broglie wavelength increases.

Question 3

How can we make the harmonic oscillator do something?

Answer 3

Drive the oscillator with incident light field

Question 4

What is the size of an atom?

Answer 4

An atom is far smaller than the wavelength of incident light

Question 5

What is the difference between the polarisability & susceptibility?

Answer 5

The polarisability is for a single atom while the susceptibility is for an ensemble of atoms.

Question 6

Light can be absorbed causing

Answer 6

. It’s amplitude to decrease

Question 7

Light can be refracted resulting in

Answer 7

It’s phase changes

Question 8

What is red detuning?

Answer 8

If the intensity increases the potential decreases resulting in high field seekers

Question 9

What is blue detuning?

Answer 9

If the intensity increases, the potential increases resulting in low field seekers

Question 10

What is the result of light scattering?

Answer 10

Atom cooling , e.g in magneto-optical traps

Question 11

What can light scatter tell us?

Answer 11

It can provide spectral information on a particular atomic transition.

Question 12

What does the absorption of light by atomic clouds tell us?

Answer 12

The absorption of light by atomic clouds allows us to measure spatial and temperature profile of trapped stones by leaving a characteristic shape?

Question 13

What is the recoil energy

Answer 13

Internal processes (absorption, emission) result in external motion (recoil). It leads to a minimum velocity change of atoms, limiting cooling.

Question 14

What happens with counter propagating light?

Answer 14

The frequency the atom sees becomes higher due to the Doppler effect. Use red detuning for most effective scattering.

Question 15

What happens with co propagating light?

Answer 15

The frequency the storm sees becomes lower due to the Doppler effect. Use blue detuning for most efficient scattering.

Question 16

What are the two main applications of atom cooling?

Answer 16

1. Atom slowers
2. Optical molasses

Question 17

What happens when we slow atoms down?

Answer 17

The effective detuning will no longer be zero, even if it was zero at the start of the cooling process.

Question 18

What is Chirp cooling?

Answer 18

When the laser frequency is adjusted to stay in resonance with atoms.

Question 19

What is the Zeeman effect?

Answer 19

When the resonance frequency is changed.

Question 20

How do we get Zeeman slowers?

Answer 20

Turn on applied magnetic field which drives transitions with circularly polarised light. In an ideal Zeeman slower the atom beam should experience a decreasing magnetic field with a Zeeman shift. The Zeeman shift exactly compensates the decreasing Doppler shift.

Question 21

What is Optical molasses?

Answer 21

A manifestation of Doppler cooling. All the sarins are resonantly cooled by a force that always opposes their motion.

Question 22

What are the limits of cooling?

Answer 22

Each absorption/emission cycle changes velocity

Spontaneous emission heats the atom

Competing effects lead to two temperature limits

Question 23

What are the two temperature limits?

Answer 23

1. The recoil temperate
2. The Doppler temperate

Question 24

What is the recoil temperature?

Answer 24

The fundamental limit below which atoms cannot be cooled with optical techniques. The photon recoil cannot systematically reduce the velocity further and the stochastic nature subsequent kicks cause heating.

Question 25

What is the Doppler temperature?

Answer 25

Arising from the balance between Doppler cooling and recoil heating. Can be overcome with sophisticated optical cooling techniques such as Sisyphus.

Question 27

What is the energy budget

Answer 27

Atoms get two recoil kicks per absorption/emission cycle. For each scattering event the energy changed by twice the recoil energy.

Question 28

What are anti-Helmholtz coils?

Answer 28

Magnetic optical traps requires magnetic field zero at its centre, and a linear magnetic field gradient in all directions

Question 29

How can we have the magnetic field point towards the trap centre?

Answer 29

Use a position dependent magnetic field as this gives rise to position dependent get levels giving a force from the gradient.

Question 30

When do we use ray optics

Answer 30

When particles are much larger than the laser wavelength

Question 31

When do we use the dipole approximation?

Answer 31

When particles are approximately the same size as the laser wavelength

Question 32

When do we use a semi classical treatment or the AC stark shift?

Answer 32

When particles are much smaller than the laser wavelength

Question 33

How does electromagnetically induced transparency work?

Answer 33

1. Light drives transitions between the coupling state and the excited state, with the Rabi frequency 2. Excited state may decay by spontaneous emission into then non-coupling state. Eventually all the atoms will be in the non- coupling state. 3. From this point on, light can no longer be absorbed by the atoms and passes unhindered through the atomic gas.

Question 34

What are the applications of EIT

Answer 34

1. magnetometer: EIT is very sensitive to frequency 2. Slow light

Question 35

What is Sisyphus cooling?

Answer 35

Sisyphus cooling requires that the atoms have at least two hyperfine levels on the ground state. The light field alternates between predominately σ+ and σ- separated by λ/4.

Question 36

What is the working principle of an atomic memory?

Answer 36

A strong pump laser modifies the atoms in the atomic cloud. The weak laser light gets slowed down and compressed. Switching off the probe allows the light to be stored.