# [SCI] Quantum Optics

**Quantum Optics** is the study of the quantum mechanical properties of light — photon statistics, coherence, entanglement, and squeezing — enabling lasers, quantum information, and precision metrology.

## Overview

Roy Glauber (1963) developed the quantum theory of optical coherence, distinguishing classical from non-classical (sub-Poissonian, squeezed) light. The development of single-photon sources, entangled photon pairs, and optical trapping (Ashkin, 1970) created tools for quantum information processing. John Bell's inequality (1964) was first tested with photons (Aspect et al., 1982), confirming quantum entanglement. Frequency combs (Hänsch, Hall, 2000s) provide the most precise clocks ever made.

## Key Figures & Recognition

- **Roy Glauber** (1925–2018): Quantum coherence theory. **Nobel Prize 2005** (shared with Hall and Hänsch).
- **John Hall** (1934–) & **Theodor Hänsch** (1941–): Optical frequency combs. **Nobel Prize 2005**.
- **Arthur Ashkin** (1922–2020): Optical tweezers. **Nobel Prize 2018**.

## Seminal Papers

- Glauber, R. "The Quantum Theory of Optical Coherence." *Phys. Rev.* 130 (1963).
- [Aspect, A., Grangier, P. & Roger, G. "Experimental Realization of Einstein-Podolsky-Rosen-Bohm Gedankenexperiment." *PRL* 49 (1982)](https://doi.org/10.1103/PhysRevLett.49.804)

## What This Enables
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- **[SCI] Quantum Computing Theory** — Photonic quantum computing, quantum key distribution, and quantum teleportation use quantum optical principles directly.
- **[TECH] Quantum Computing Hardware** — Photonic qubits, squeezed-light sensing, and entangled photon sources are quantum optics hardware.
- **[TECH] LIGO Gravitational Wave Detector** — LIGO operates at the quantum noise limit; squeezed light injection (a quantum optics technique) improves sensitivity.
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# Parents

* [SCI] Laser Physics & Stimulated Emission
* [SCI] Laser Physics & Stimulated Emission