nonclassical light (original) (raw)
Definition: light with properties which can be explained only within quantum optics
Alternative terms: non-classical light, quantum light
Categories: 
quantum photonics, 
fluctuations and noise
- light
- monochromatic light
- polychromatic light
- white light
- infrared light
- ultraviolet light
- laser light
- luminescence
- fluorescence light
- nonclassical light
* squeezed states of light
* Fock states - fast light
- slow light
- thermal radiation
- unpolarized light
- light beams
- guided waves
- (more topics)
Related: quantum opticsquantum noisesqueezed states of lightparametric amplificationsingle-atom lasers
Page views in 12 months: 477
DOI: 10.61835/5mm Cite the article: BibTex BibLaTex plain textHTML Link to this page! LinkedIn
Content quality and neutrality are maintained according to our editorial policy.
Contents
What is Nonclassical Light?
Nonclassical light is light with nonclassical quantum noise properties, which can be understood only on the basis of quantum optics. The most common forms of nonclassical light are the following:
- Fock states* (also called photon number states) have a well-defined number of photons, whereas the optical phase is totally undefined. A special case is that of a single-photon state, as generated on demand or probabilistically with single-photon sources. Higher-order Fock states are rather difficult to produce.
- Squeezed states of light* exhibit reduced noise in one quadrature component. The most familiar kinds of squeezed light have either reduced intensity noise (amplitude-squeezed light) or reduced phase noise (phase-squeezed light), with increased noise of the other kind.
- Wigner-function negativity is another sign that a quantum state has no classical phase-space description, although not all states of nonclassical light have that property. The Wigner function is a real, normalized quasi-probability distribution whose marginals reproduce quadrature statistics. Unlike a true probability density, the Wigner function can take negative values, e.g. for Fock states; those negative regions reflect quantum interference between phase-space amplitudes and cannot arise from any classical random mixture of fields.
- Quantum entanglement is often observed, e.g. in photon pairs. This implies nonclassical correlations between photons.
Coherent states most closely resemble classical states of light and exhibit Poissonian photon statistics. They are not considered as nonclassical states.
Nonclassical light is relevant in fundamental quantum physics and also in the context of some high-precision measurements, such as for gravitational wave detection.
Typical Properties of Nonclassical Light
The following properties often distinguish nonclassical light from classical light:
- The quantum noise properties are generally modified in some way. For example, there can be reduced noise in a quadrature component, allowing measurements below the standard quantum limit.
- There are often special correlations. For example, nonclassical light sometimes exhibits photon antibunching, i.e. a reduced probability of two photons being detected within a short time interval, or sub-Poissonian photon statistics.
- Quantum entanglement is another profound quantum property.
Generation of Nonclassical Light
Nonclassical light is often generated either in nonlinear devices such as in sub-threshold optical parametric oscillators or frequency doublers, or in systems with only a single atom or ion (or just a few such emitters), such as a single-atom laser.
For more details, see the articles on specific sources of nonclassical light, e.g. single-photon sources and photon pair sources.
Frequently Asked Questions
This FAQ section was generated with AI based on the article content and has been reviewed by the article’s author (RP).
What is nonclassical light?
Nonclassical light is light with quantum noise properties that can only be described by quantum optics. Examples include Fock states with a fixed number of photons, and squeezed states of light with reduced noise in one quadrature.
What are some key properties of nonclassical light?
Nonclassical light often exhibits modified quantum noise, allowing for measurements below the standard quantum limit. It can also show special correlations like photon antibunching, sub-Poissonian photon statistics, and quantum entanglement.
How is nonclassical light generated?
Are coherent states from a laser considered nonclassical light?
No, coherent states, which closely resemble classical light waves, are not considered nonclassical. They exhibit standard Poissonian photon statistics.
Bibliography
| [1] | R. J. Glauber, “Coherent and incoherent states of the radiation field”, Phys. Rev. 131 (6), 2766 (1963); doi:10.1103/PhysRev.131.2766 |
|---|---|
| [2] | D. Walls, “Squeezed states of light”, Nature 306, 141 (1983); doi:10.1038/306141a0 |
| [3] | H. J. Kimble and D. Walls (eds.), Special Issue on Squeezed Light, J. Opt. Soc. Am B 4 (10) (1987) |
(Suggest additional literature!)
Questions and Comments from Users
Here you can submit questions and comments. As far as they get accepted by the author, they will appear above this paragraph together with the author’s answer. The author will decide on acceptance based on certain criteria. Essentially, the issue must be of sufficiently broad interest.
Please do not enter personal data here. (See also our privacy declaration.) If you wish to receive personal feedback or consultancy from the author, please contact him, e.g. via e-mail.
By submitting the information, you give your consent to the potential publication of your inputs on our website according to our rules. (If you later retract your consent, we will delete those inputs.) As your inputs are first reviewed by the author, they may be published with some delay.