A laser is a device that generates light that is particularly focused, powerful, and uniform. Unlike normal light, which is scattered in many directions and consists of many different colors, laser light is very sharply focused and, ideally, consists of only one single color.
Lasers have many practical applications: they are used in CD and DVD players, barcode scanners, laser cutting machines, eye surgery, and measuring devices. Lasers also play an important role in research because their light can be controlled so precisely.
In quantum physics, lasers are extremely important tools because they can provide the very precise, controlled light needed for experiments at the quantum level.
Some important applications are:
- Cooling and trapping atoms: Lasers can be used to slow atoms down significantly and trap them in a so-called optical lattice or magneto-optical trap. This is necessary in order to study their quantum mechanical properties in detail.
- Manipulation of quantum states: Lasers can be used to excite, shift, or bring individual atoms or photons into specific quantum states. This allows quantum computer bits (qubits) to be controlled.
- Generation of entangled photons: Laser light is used in special crystals to generate intertwined or entangled photon pairs, which are necessary for quantum communication and quantum cryptography.
- Precision measurements: Lasers enable extremely accurate measurements of distances, frequencies, or time units, e.g., in atomic clocks or in the detection of tiny forces and fields.