Book contents
- Frontmatter
- Contents
- Preface
- 1 Introduction
- 2 Historical milestones
- 3 Basics of the classical description of light
- 4 Quantum mechanical understanding of light
- 5 Light detectors
- 6 Spontaneous emission
- 7 Interference
- 8 Photon statistics
- 9 Squeezed light
- 10 Measuring distribution functions
- 11 Optical Einstein–Podolsky–Rosen experiments
- 12 Quantum cryptography
- 13 Quantum teleportation
- 14 Summarizing what we know about the photon
- 15 Appendix. Mathematical description
- References
- Index
6 - Spontaneous emission
Published online by Cambridge University Press: 25 January 2010
- Frontmatter
- Contents
- Preface
- 1 Introduction
- 2 Historical milestones
- 3 Basics of the classical description of light
- 4 Quantum mechanical understanding of light
- 5 Light detectors
- 6 Spontaneous emission
- 7 Interference
- 8 Photon statistics
- 9 Squeezed light
- 10 Measuring distribution functions
- 11 Optical Einstein–Podolsky–Rosen experiments
- 12 Quantum cryptography
- 13 Quantum teleportation
- 14 Summarizing what we know about the photon
- 15 Appendix. Mathematical description
- References
- Index
Summary
Particle properties of radiation
One of the most important properties of macroscopic material systems is their ability to emit radiation spontaneously. According to quantum mechanics, the emission process is realized in the following way: an atom (or a molecule) makes a transition from a higher lying energy level (to which it was brought, for example, by an electron collision) to a lower lying energy level without any noticeable external influence (in the form of an existing electromagnetic field), and the released energy is emitted in the form of electromagnetic radiation. The discrete energy structure of the atom dictated by the laws of quantum mechanics is imprinted also on the emission process (quantization of the emission energy), since the energy conservation law is also valid for single (individual) transitions. Hence, a single photon, in the sense of a well defined energy quantum, is always emitted.
The emitted quanta can be directly detected by a photodetector. (Strictly speaking, identifying a registered photon with an emitted one is possible only when it is guaranteed that the observed volume contains only a single atom. (For details see Sections 6.8 and 8.1.) Under realistic conditions, the experiment can be performed in the following way. First, a beam of ionized atoms is sent through a thin foil; the emerging beam then consists of excited atoms. (This procedure is known as the beam–foil technique.) A detector is placed at a distance d from the foil to detect light emitted sideways by the atomic beam (Fig. 6.1).
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- Introduction to Quantum OpticsFrom Light Quanta to Quantum Teleportation, pp. 59 - 86Publisher: Cambridge University PressPrint publication year: 2004