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High efficiency coherent optical memory with warm rubidium vapour.

Hosseini M, Sparkes BM, Campbell G, Lam PK, Buchler BC - Nat Commun (2011)

Bottom Line: Here, we present results from a coherent optical memory based on warm rubidium vapour and show 87% efficient recall of light pulses, the highest efficiency measured to date for any coherent optical memory suitable for quantum information applications.We also show storage and recall of up to 20 pulses from our system.These results show that simple warm atomic vapour systems have clear potential as a platform for quantum memory.

View Article: PubMed Central - PubMed

Affiliation: ARC Centre of Excellence for Quantum Atom Optics, Department of Quantum Science, The Australian National University, Canberra, ACT 0200, Australia.

ABSTRACT
By harnessing aspects of quantum mechanics, communication and information processing could be radically transformed. Promising forms of quantum information technology include optical quantum cryptographic systems and computing using photons for quantum logic operations. As with current information processing systems, some form of memory will be required. Quantum repeaters, which are required for long distance quantum key distribution, require quantum optical memory as do deterministic logic gates for optical quantum computing. Here, we present results from a coherent optical memory based on warm rubidium vapour and show 87% efficient recall of light pulses, the highest efficiency measured to date for any coherent optical memory suitable for quantum information applications. We also show storage and recall of up to 20 pulses from our system. These results show that simple warm atomic vapour systems have clear potential as a platform for quantum memory.

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Schematic view of the experiment.(a) Schematic view of the frequency gradient generated for an ensemble of two-level atoms. By switching the sign of the gradient from positive (left) to negative (right) a photon-echo is emitted in the forward direction. (b) Schematic view of Λ-atom structure, which at large detuning is equivalent to a two-level atom based on the two ground states. (c) Experimental setup showing the control (red) and signal (blue) beams with 6.8 GHz frequency difference, collimated at radii of 6 and 3 mm, respectively, and of identical circular polarization when they go through the cell. Heterodyne measurement is performed after the memory on the signal field. AOM, acousto-optic modulator; BS, beam splitter; FC-EOM, fibre-coupled electro-optic modulator; HD, heterodyne detection; SMF: single-mode fibre; ɛs and ɛc, signal and control field amplitudes, respectively.
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f1: Schematic view of the experiment.(a) Schematic view of the frequency gradient generated for an ensemble of two-level atoms. By switching the sign of the gradient from positive (left) to negative (right) a photon-echo is emitted in the forward direction. (b) Schematic view of Λ-atom structure, which at large detuning is equivalent to a two-level atom based on the two ground states. (c) Experimental setup showing the control (red) and signal (blue) beams with 6.8 GHz frequency difference, collimated at radii of 6 and 3 mm, respectively, and of identical circular polarization when they go through the cell. Heterodyne measurement is performed after the memory on the signal field. AOM, acousto-optic modulator; BS, beam splitter; FC-EOM, fibre-coupled electro-optic modulator; HD, heterodyne detection; SMF: single-mode fibre; ɛs and ɛc, signal and control field amplitudes, respectively.

Mentions: In our work, we use the Gradient Echo Memory (GEM) scheme. The key to GEM is the use of an external field that induces a linear atomic frequency gradient in the direction of propagation. The frequency gradient means that the spectral components of the input light are encoded linearly along the length of the cell. Modelling has recently shown how this frequency encoding nature of GEM can be used to manipulate stored information allowing spectral compression, frequency splitting and fine dispersion control of pulses while they are stored in the memory16. Recall is achieved without π-pulses simply by reversing the field gradient (see Fig. 1a). This technique has been implemented in two-level praseodymium ions where recall efficiencies of 69% have been shown17. In this solid state system, the frequency gradient is applied using an electric field to induce a Stark shift. Furthermore using AFC it has been demonstrated that optical information can be mapped into ground states of praseodymium atoms doped into crystal18. The GEM scheme has also been adapted to three-level Λ structured atoms (Fig. 1b). This protocol makes it possible to reorder a stored pulse sequence allowing recall of any individual pulse at any chosen time19. This approach could work as an optical random-access memory for quantum information encoded in time-bin qubits. The Λ-GEM scheme uses long-lived atomic ground states for storage allowing a substantial increase of memory lifetimes compared with two-level GEM2021. Using ground state coherences also enables a wider range of atomic systems, such as alkali atomic ensembles, which are easy to address with diode laser systems and can be contained in simple off-the-shelf vapour cells. Furthermore, it has recently been shown that vapour cells can be prepared with a single compound alkene based coating to achieve spin relaxation times of the order of few seconds22.


High efficiency coherent optical memory with warm rubidium vapour.

Hosseini M, Sparkes BM, Campbell G, Lam PK, Buchler BC - Nat Commun (2011)

Schematic view of the experiment.(a) Schematic view of the frequency gradient generated for an ensemble of two-level atoms. By switching the sign of the gradient from positive (left) to negative (right) a photon-echo is emitted in the forward direction. (b) Schematic view of Λ-atom structure, which at large detuning is equivalent to a two-level atom based on the two ground states. (c) Experimental setup showing the control (red) and signal (blue) beams with 6.8 GHz frequency difference, collimated at radii of 6 and 3 mm, respectively, and of identical circular polarization when they go through the cell. Heterodyne measurement is performed after the memory on the signal field. AOM, acousto-optic modulator; BS, beam splitter; FC-EOM, fibre-coupled electro-optic modulator; HD, heterodyne detection; SMF: single-mode fibre; ɛs and ɛc, signal and control field amplitudes, respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3105315&req=5

f1: Schematic view of the experiment.(a) Schematic view of the frequency gradient generated for an ensemble of two-level atoms. By switching the sign of the gradient from positive (left) to negative (right) a photon-echo is emitted in the forward direction. (b) Schematic view of Λ-atom structure, which at large detuning is equivalent to a two-level atom based on the two ground states. (c) Experimental setup showing the control (red) and signal (blue) beams with 6.8 GHz frequency difference, collimated at radii of 6 and 3 mm, respectively, and of identical circular polarization when they go through the cell. Heterodyne measurement is performed after the memory on the signal field. AOM, acousto-optic modulator; BS, beam splitter; FC-EOM, fibre-coupled electro-optic modulator; HD, heterodyne detection; SMF: single-mode fibre; ɛs and ɛc, signal and control field amplitudes, respectively.
Mentions: In our work, we use the Gradient Echo Memory (GEM) scheme. The key to GEM is the use of an external field that induces a linear atomic frequency gradient in the direction of propagation. The frequency gradient means that the spectral components of the input light are encoded linearly along the length of the cell. Modelling has recently shown how this frequency encoding nature of GEM can be used to manipulate stored information allowing spectral compression, frequency splitting and fine dispersion control of pulses while they are stored in the memory16. Recall is achieved without π-pulses simply by reversing the field gradient (see Fig. 1a). This technique has been implemented in two-level praseodymium ions where recall efficiencies of 69% have been shown17. In this solid state system, the frequency gradient is applied using an electric field to induce a Stark shift. Furthermore using AFC it has been demonstrated that optical information can be mapped into ground states of praseodymium atoms doped into crystal18. The GEM scheme has also been adapted to three-level Λ structured atoms (Fig. 1b). This protocol makes it possible to reorder a stored pulse sequence allowing recall of any individual pulse at any chosen time19. This approach could work as an optical random-access memory for quantum information encoded in time-bin qubits. The Λ-GEM scheme uses long-lived atomic ground states for storage allowing a substantial increase of memory lifetimes compared with two-level GEM2021. Using ground state coherences also enables a wider range of atomic systems, such as alkali atomic ensembles, which are easy to address with diode laser systems and can be contained in simple off-the-shelf vapour cells. Furthermore, it has recently been shown that vapour cells can be prepared with a single compound alkene based coating to achieve spin relaxation times of the order of few seconds22.

Bottom Line: Here, we present results from a coherent optical memory based on warm rubidium vapour and show 87% efficient recall of light pulses, the highest efficiency measured to date for any coherent optical memory suitable for quantum information applications.We also show storage and recall of up to 20 pulses from our system.These results show that simple warm atomic vapour systems have clear potential as a platform for quantum memory.

View Article: PubMed Central - PubMed

Affiliation: ARC Centre of Excellence for Quantum Atom Optics, Department of Quantum Science, The Australian National University, Canberra, ACT 0200, Australia.

ABSTRACT
By harnessing aspects of quantum mechanics, communication and information processing could be radically transformed. Promising forms of quantum information technology include optical quantum cryptographic systems and computing using photons for quantum logic operations. As with current information processing systems, some form of memory will be required. Quantum repeaters, which are required for long distance quantum key distribution, require quantum optical memory as do deterministic logic gates for optical quantum computing. Here, we present results from a coherent optical memory based on warm rubidium vapour and show 87% efficient recall of light pulses, the highest efficiency measured to date for any coherent optical memory suitable for quantum information applications. We also show storage and recall of up to 20 pulses from our system. These results show that simple warm atomic vapour systems have clear potential as a platform for quantum memory.

Show MeSH
Related in: MedlinePlus