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. Bustard, Jennifer Erskine, Duncan G. England, Josh Nunn, Paul Hockett, Rune Lausten, Michael Spanner, and Benjamin J. Sussman Source article Abstract | Full Text: XHTML | Full Text: PDF http://www.opticsinfobase.org/spotlight/summary.cfm?URI=ol-40-6-922

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

Abstract-Toward Quantum Processing in Molecules: A THz-Bandwidth Coherent Memory for Light

Philip J. Bustard, Rune Lausten, Duncan G. England, and Benjamin J. Sussman^* 
National Research Council of Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6, Canada

http://prl.aps.org/abstract/PRL/v111/i8/e083901

The unusual features of quantum mechanics are enabling the development of technologies not possible with classical physics. These devices utilize nonclassical phenomena in the states of atoms, ions, and solid-state media as the basis for many prototypes. Here we investigate molecular states as a distinct alternative. We demonstrate a memory for light based on storing photons in the vibrations of hydrogen molecules. The THz-bandwidth molecular memory is used to store 100-fs pulses for durations up to ∼1  ns, enabling ∼10⁴ operational time bins. The results demonstrate the promise of molecules for constructing compact ultrafast quantum photonic technologies.

Synopsis: Molecular Memory for Light

Toward Quantum Processing in Molecules: A THz-Bandwidth Coherent Memory for Light

http://physics.aps.org/synopsis-for/10.1103/PhysRevLett.111.083901

Philip J. Bustard, Rune Lausten, Duncan G. England, and Benjamin J. Sussman

Phys. Rev. Lett. 111, 083901 (2013)

Published August 19, 2013

Quantum processors, like their classical counterparts, will need fast and reliable memories to store and retrieve information as superpositions of states. Researchers are pursuing several photonic technologies, among others, to achieve this by storing quantum information in specially prepared solids, ions, and atomic vapors. Philip Bustard and colleagues at the National Research Council (NRC) of Canada, Ontario, have now investigated another kind of storage medium: the vibrational modes of molecules. Their experiments, published in Physical Review Letters, demonstrate that the system can act as a fast and efficient molecular quantum memory.