Monday, March 16, 2015

SPOTLIGHT-Nonclassical correlations between terahertz-bandwidth photons mediated by rotational quanta in hydrogen molecules

Nonclassical correlations between terahertz-bandwidth photons mediated by rotational quanta in hydrogen molecules

Published in Optics Letters, Vol. 40 Issue 6, pp.922-925 (2015)
by Philip J. BustardJennifer ErskineDuncan G. EnglandJosh NunnPaul HockettRune LaustenMichael Spanner, and Benjamin J. Sussman
Source article Abstract | Full Text: XHTML | Full Text: PDF

Spotlight summary: The development of information technology relying on quantum physical properties is attracting more and more interest with the goal of everyday technologies relying on quantum computation principles. Photonics is showing promise of long-lived quantum states and fast manipulation of them.

The authors demonstrate a Duan, Lukin, Cirac and Zoller (DLCZ) emission memory protocol with a Delocalized Rotation Quantum written on hydrogen molecules. The protocol is based on rotational Raman scattering between ground and excited states (both degenerate). A gas cell containing Hydrogen receives a first left circular pulse (write pulse), generating spontaneous Raman Scattering right polarized photons upon reaching the excited states, then with various delays the cell receives a second right polarized pulse (read pulse), generating a left polarized Anti-Raman scattering photons when reaching the ground states. The emitted photons are freed from the pump radiation by a notch filter and then split by a dichroic mirror. Photons are then sorted on both paths based on polarization and a coincidence counting module allows events detection.

The Delocalized Rotational Quanta couple the Raman and Anti Raman photons emission. The existence of the delocalised rotational quanta is characterized through the temporal evolution of the normalized intensity of the Stokes and anti-Stokes cross correlation function g(2)S,A, that deviates from classical domain values for ~100ps. This deviation is the sign of the coupling between Raman and Anti Raman photons. The limitation of the coherence time is due to mechanical collision of hydrogen molecules, which depends on the pressure and temperature of the gas cell.

The possibility of creating “quantum states” at normal temperature is appealing for the development of “user-friendly” quantum based technologies. Yet, challenges remain for the use of these technologies such as appropriate lifetime of the memory for various applications and limitations imposed by frequency dependent dispersal properties of various optical media.

--Jean-Baptiste Masson

Technical Division: Light–Matter Interactions
ToC Category: Quantum Optics
OCIS Codes:(020.1670) Atomic and molecular physics : Coherent optical effects
(270.1670) Quantum optics : Coherent optical effects
(290.5860) Scattering : Scattering, Raman
(320.7110) Ultrafast optics : Ultrafast nonlinear optics

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