Limits...
Scalable photonic network architecture based on motional averaging in room temperature gas.

Borregaard J, Zugenmaier M, Petersen JM, Shen H, Vasilakis G, Jensen K, Polzik ES, Sørensen AS - Nat Commun (2016)

Bottom Line: Thermal atomic vapours, which present a simple and scalable resource, have only been used for continuous variable processing or for discrete variable processing on short timescales where atomic motion is negligible.Here we develop a theory based on motional averaging to enable room temperature discrete variable quantum memories and coherent single-photon sources.We demonstrate the feasibility of this approach to scalable quantum memories with a proof-of-principle experiment with room temperature atoms contained in microcells with spin-protecting coating, placed inside an optical cavity.

View Article: PubMed Central - PubMed

Affiliation: The Niels Bohr Institute, University of Copenhagen, Blegdamsvej 17, Copenhagen Ø DK-2100, Denmark.

ABSTRACT
Quantum interfaces between photons and atomic ensembles have emerged as powerful tools for quantum technologies. Efficient storage and retrieval of single photons requires long-lived collective atomic states, which is typically achieved with immobilized atoms. Thermal atomic vapours, which present a simple and scalable resource, have only been used for continuous variable processing or for discrete variable processing on short timescales where atomic motion is negligible. Here we develop a theory based on motional averaging to enable room temperature discrete variable quantum memories and coherent single-photon sources. We demonstrate the feasibility of this approach to scalable quantum memories with a proof-of-principle experiment with room temperature atoms contained in microcells with spin-protecting coating, placed inside an optical cavity. The experimental conditions correspond to a few photons per pulse and a long coherence time of the forward scattered photons is demonstrated, which is the essential feature of the motional averaging.

No MeSH data available.


Related in: MedlinePlus

Proof-of-principle experiment.(a) Schematic representation of the proof-of-principle experiment. (b) The D2 transition probed in the proof-of-principle experiment. (c) Effective coupling scheme for the Faraday interaction13. The strong probe beam (straight arrows) is polarized perpendicular to the applied field and can thus drive σ+ and σ− transition. An atom scattered between two different mF levels results in a π polarized photon (wiggly lines), orthogonal to the drive. In the weak probing limit, the measurement of the Faraday rotation angle is thus equivalent to a heterodyne measurement of the emitted light in the Raman transition with the probe pulse acting as a local oscillator. BS, beam splitter; CM, cavity mirror; PBS, polarizing beam splitter; PD, photodiode.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4834638&req=5

f4: Proof-of-principle experiment.(a) Schematic representation of the proof-of-principle experiment. (b) The D2 transition probed in the proof-of-principle experiment. (c) Effective coupling scheme for the Faraday interaction13. The strong probe beam (straight arrows) is polarized perpendicular to the applied field and can thus drive σ+ and σ− transition. An atom scattered between two different mF levels results in a π polarized photon (wiggly lines), orthogonal to the drive. In the weak probing limit, the measurement of the Faraday rotation angle is thus equivalent to a heterodyne measurement of the emitted light in the Raman transition with the probe pulse acting as a local oscillator. BS, beam splitter; CM, cavity mirror; PBS, polarizing beam splitter; PD, photodiode.

Mentions: The experimental setup is shown in Fig. 4 and is further explained in the Methods section. A DC bias magnetic field perpendicular to the probe direction sets the Larmor frequency of the atoms. Because of technical limitations related with the phase noise of the laser and the cell birefringence, the polarization of the probe was at an angle of ∼40–45° with respect to the axis of the magnetic field. When the probe light is far detuned, the Faraday rotation is, however, independent of this angle13. For simplicity, we therefore describe the dynamics using the level structure in Fig. 4c, which assumes that the driving field is σ++σ− polarized, perpendicular to the direction of the magnetic field π. In the far-detuned limit, the Faraday rotation is due to Raman transitions between magnetic states with magnetic quantum numbers mF differing by ±1. In these Raman transitions, a π-polarized photon is emitted as shown in Fig. 4c. In the balanced polarimetry, the driving field and the scattered π component of the light are mixed on a polarizing beam splitter and the difference intensity is recorded. This corresponds to the driving field acting as local oscillator for a heterodyne measurement of the emitted π-polarized light. The recorded Raman noise is thus a measurement of the photons emitted from the atoms through Raman scattering between the Zeeman sublevels of the Cs hyperfine manifolds and is therefore exactly the quantity we are interested in for probing the coherence of the emitted photons and verifying the predictions of the model. The experiment is performed in the continuous regime with constant laser intensity. By comparing the emitted light to the shot-noise level, we can extract the Raman scattering rate. For a pulse duration that can lead to an efficient write step, for example, , corresponding to κ2=2π·15 kHz in Fig. 3a, we find that approximately eight Raman photons are scattered in the upper sideband mode (see Supplementary Methods and Supplementary Fig. 2). Because of the linearity of the process, the spectrum is expected to be the same at the single-photon level.


Scalable photonic network architecture based on motional averaging in room temperature gas.

Borregaard J, Zugenmaier M, Petersen JM, Shen H, Vasilakis G, Jensen K, Polzik ES, Sørensen AS - Nat Commun (2016)

Proof-of-principle experiment.(a) Schematic representation of the proof-of-principle experiment. (b) The D2 transition probed in the proof-of-principle experiment. (c) Effective coupling scheme for the Faraday interaction13. The strong probe beam (straight arrows) is polarized perpendicular to the applied field and can thus drive σ+ and σ− transition. An atom scattered between two different mF levels results in a π polarized photon (wiggly lines), orthogonal to the drive. In the weak probing limit, the measurement of the Faraday rotation angle is thus equivalent to a heterodyne measurement of the emitted light in the Raman transition with the probe pulse acting as a local oscillator. BS, beam splitter; CM, cavity mirror; PBS, polarizing beam splitter; PD, photodiode.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4834638&req=5

f4: Proof-of-principle experiment.(a) Schematic representation of the proof-of-principle experiment. (b) The D2 transition probed in the proof-of-principle experiment. (c) Effective coupling scheme for the Faraday interaction13. The strong probe beam (straight arrows) is polarized perpendicular to the applied field and can thus drive σ+ and σ− transition. An atom scattered between two different mF levels results in a π polarized photon (wiggly lines), orthogonal to the drive. In the weak probing limit, the measurement of the Faraday rotation angle is thus equivalent to a heterodyne measurement of the emitted light in the Raman transition with the probe pulse acting as a local oscillator. BS, beam splitter; CM, cavity mirror; PBS, polarizing beam splitter; PD, photodiode.
Mentions: The experimental setup is shown in Fig. 4 and is further explained in the Methods section. A DC bias magnetic field perpendicular to the probe direction sets the Larmor frequency of the atoms. Because of technical limitations related with the phase noise of the laser and the cell birefringence, the polarization of the probe was at an angle of ∼40–45° with respect to the axis of the magnetic field. When the probe light is far detuned, the Faraday rotation is, however, independent of this angle13. For simplicity, we therefore describe the dynamics using the level structure in Fig. 4c, which assumes that the driving field is σ++σ− polarized, perpendicular to the direction of the magnetic field π. In the far-detuned limit, the Faraday rotation is due to Raman transitions between magnetic states with magnetic quantum numbers mF differing by ±1. In these Raman transitions, a π-polarized photon is emitted as shown in Fig. 4c. In the balanced polarimetry, the driving field and the scattered π component of the light are mixed on a polarizing beam splitter and the difference intensity is recorded. This corresponds to the driving field acting as local oscillator for a heterodyne measurement of the emitted π-polarized light. The recorded Raman noise is thus a measurement of the photons emitted from the atoms through Raman scattering between the Zeeman sublevels of the Cs hyperfine manifolds and is therefore exactly the quantity we are interested in for probing the coherence of the emitted photons and verifying the predictions of the model. The experiment is performed in the continuous regime with constant laser intensity. By comparing the emitted light to the shot-noise level, we can extract the Raman scattering rate. For a pulse duration that can lead to an efficient write step, for example, , corresponding to κ2=2π·15 kHz in Fig. 3a, we find that approximately eight Raman photons are scattered in the upper sideband mode (see Supplementary Methods and Supplementary Fig. 2). Because of the linearity of the process, the spectrum is expected to be the same at the single-photon level.

Bottom Line: Thermal atomic vapours, which present a simple and scalable resource, have only been used for continuous variable processing or for discrete variable processing on short timescales where atomic motion is negligible.Here we develop a theory based on motional averaging to enable room temperature discrete variable quantum memories and coherent single-photon sources.We demonstrate the feasibility of this approach to scalable quantum memories with a proof-of-principle experiment with room temperature atoms contained in microcells with spin-protecting coating, placed inside an optical cavity.

View Article: PubMed Central - PubMed

Affiliation: The Niels Bohr Institute, University of Copenhagen, Blegdamsvej 17, Copenhagen Ø DK-2100, Denmark.

ABSTRACT
Quantum interfaces between photons and atomic ensembles have emerged as powerful tools for quantum technologies. Efficient storage and retrieval of single photons requires long-lived collective atomic states, which is typically achieved with immobilized atoms. Thermal atomic vapours, which present a simple and scalable resource, have only been used for continuous variable processing or for discrete variable processing on short timescales where atomic motion is negligible. Here we develop a theory based on motional averaging to enable room temperature discrete variable quantum memories and coherent single-photon sources. We demonstrate the feasibility of this approach to scalable quantum memories with a proof-of-principle experiment with room temperature atoms contained in microcells with spin-protecting coating, placed inside an optical cavity. The experimental conditions correspond to a few photons per pulse and a long coherence time of the forward scattered photons is demonstrated, which is the essential feature of the motional averaging.

No MeSH data available.


Related in: MedlinePlus