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Quantum technologies

Dieter Meschede's research group
Home Fibre cavity QED People Deepak Pandey
People - Fibre cavity QED
Dr. Deepak Pandey
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Fibre cavity QED

Publications(up to 2021)

  • C. Saavedra, D. Pandey, W. Alt, H. Pfeifer and D. Meschede
    Tunable fiber Fabry-Perot cavities with high passive stability, Optics Express 29, 974 (2021)arXivBibTeXPDF

    We present three high finesse tunable monolithic fiber Fabry-Perot cavities (FFPCs) with high passive mechanical stability. The fiber mirrors are fixed inside slotted glass ferrules, which guarantee an inherent alignment of the resonators. An attached piezoelectric element enables fast tuning of the FFPC resonance frequency over the entire free-spectral range for two of the designs. Stable locking of the cavity resonance is achieved for sub-Hertz feedback bandwidths, demonstrating the high passive stability. At the other limit, locking bandwidths up to tens of kilohertz, close to the first mechanical resonance, can be obtained. The root-mean-square frequency fluctuations are suppressed down to ∼2% of the cavity linewidth. Over a wide frequency range, the frequency noise is dominated by the thermal noise limit of the system’s mechanical resonances. The demonstrated small footprint devices can be used advantageously in a broad range of applications like cavity-based sensing techniques, optical filters or quantum light-matter interfaces.

  • E. Uruñuela, W. Alt, E. Keiler, D. Meschede, D. Pandey, H. Pfeifer and T. Macha
    Ground-State Cooling of a Single Atom in a High-Bandwidth Cavity, Phys. Rev. A 101, 023415 (2020)arXivBibTeXPDF

    We report on vibrational ground-state cooling of a single neutral atom coupled to a high-bandwidth Fabry-Pérot cavity. The cooling process relies on degenerate Raman sideband transitions driven by dipole trap beams, which confine the atoms in three dimensions. We infer a one-dimensional motional ground-state population close to 90% by means of Raman spectroscopy. Moreover, lifetime measurements of a cavity-coupled atom exceeding 40 s imply three-dimensional cooling of the atomic motion, which makes this resource-efficient technique particularly interesting for cavity experiments with limited optical access.

  • T. Macha, E. Uruñuela, W. Alt, M. Ammenwerth, D. Pandey, H. Pfeifer and D. Meschede
    Non-adiabatic Storage of Short Light Pulses in an Atom-Cavity System, Phys. Rev. A 101, 053406 (2020)arXivBibTeXPDF

    We demonstrate the storage of 5 ns light pulses in a single rubidium atom coupled to a fiber-based optical resonator. Our storage protocol addresses a regime beyond the conventional adiabatic limit and approaches the theoretical bandwidth limit. We extract the optimal control laser pulse properties from a numerical simulation of our system and measure storage efficiencies of (8.1±1.1)%, in close agreement with the maximum expected efficiency. Such well-controlled and high-bandwidth atom-photon interfaces are key components for future hybrid quantum networks.

  • J. Gallego, W. Alt, T. Macha, M. Martinez-Dorantes, D. Pandey and D. Meschede
    Strong Purcell effect on a neutral atom trapped in an open fiber cavity, Phys. Rev. Lett. 121, 17360 (2018)arXivBibTeXPDF

    We observe a sixfold Purcell broadening of the D2 line of an optically trapped 87Rb atom strongly coupled to a fiber cavity. Under external illumination by a near-resonant laser, up to 90% of the atom's fluorescence is emitted into the resonant cavity mode. The sub-Poissonian statistics of the cavity output and the Purcell enhancement of the atomic decay rate are confirmed by the observation of a strongly narrowed antibunching dip in the photon autocorrelation function. The photon leakage through the higher-transmission mirror of the single-sided resonator is the dominant contribution to the field decay (κ≈2π×50 MHz), thus offering a high-bandwidth, fiber-coupled channel for photonic interfaces such as quantum memories and single-photon sources.

Open projects