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We report a single-stage bidirectional interface capable of linking Sr+ trapped-ion qubits in a long-distance quantum network. Our interface converts photons between the Sr+ emission wavelength at 422 nm and the telecom C band to enable low-loss transmission over optical fiber. We have achieved both up- and down-conversion at the single-photon level with efficiencies of 9.4% and 1.1%, respectively. Furthermore, we demonstrate noise levels that are low enough to allow for genuine quantum operation in the future.

Achieving cavity-optomechanical strong coupling with high-frequency phonons provides a rich avenue for quantum technology development including quantum state-transfer, memory, and transduction, as well as enabling several fundamental studies of macroscopic phononic degrees-of-freedom. Reaching such coupling with GHz mechanical modes however has proved challenging, with a prominent hindrance being material- and surface-induced-optical absorption in many materials. Here, we circumvent these challenges and report the observation of optomechanical strong coupling to a high frequency (11 GHz) mechanical mode of a fused-silica whispering-gallery microresonator via the electrostrictive Brillouin interaction. Using an optical heterodyne detection scheme, the anti-Stokes light backscattered from the resonator is measured and normal-mode splitting and an avoided crossing are observed in the recorded spectra, providing unambiguous signatures of strong coupling. The optomechanical coupling rate reaches values as high as $G/2\pi = 39 \ \text{MHz}$ through the use of an auxiliary pump resonance, where the coupling dominates both the optical ($\kappa/2\pi = 3 \ \text{MHz}$) and the mechanical ($\gamma_\text{m}/2\pi = 21 \ \text{MHz}$) amplitude decay rates. Our findings provide a promising new approach for optical quantum control using light and sound., Comment: 16 pages, 5 figures, includes supplementary, accepted in Optica

Broadband quantum memories, used as temporal multiplexers, are a key component in photonic quantum information processing, as they make repeat-until-success strategies scalable. We demonstrate a prototype system, operating on-demand, by interfacing a warm vapour, high time-bandwidth-product Raman memory with a travelling wave spontaneous parametric down-conversion source. We store single photons and observe a clear influence of the input photon statistics on the retrieved light, which we find currently to be limited by noise. We develop a theoretical model that identifies four-wave mixing as the sole important noise source and point towards practical solutions for noise-free operation.

High Harmonic generation can be used as a probe of the emitting medium with attosecond and Angstrom resolutions. We show that polarization-resolved pump-probe spectroscopy with high harmonics improves the detection sensitivity of rotationally excited molecules.

We address an optical quantum memory with multiple pulses, enabling unit efficiency readout and programmable beam splitting. The resulting coherent processor with built-in storage is universal for scalable photonic quantum information processing. © 2012 OSA.

Applied research into quantum technologies and fundamental research into the foundations of quantum mechanics run hand in hand, since our understanding of quantum correlations both advances, and is advanced by, our ability to control large quantum systems. The off-resonant Raman interaction of light with material systems provides a powerful tool both for quantum information processing, and for accessing macroscopic non-classical states of matter. We describe a recent demonstration of entanglement between the motion of separated diamond crystals at room temperature, and the implementation of quantum memories in cesium vapour that can store and retrieve photons on demand with a time-bandwidth product exceeding 2000, both based on Raman scattering. © 2013 IEEE., 2013 IEEE Photonics Society Summer Topical Meeting Series, PSSTMS 2013, July 8-10, 2013, Waikoloa, HI, USA

We present the joint photon-number statistics of a locally photon-subtracted two-mode vacuum squeezed state of light. Comparison to the unsubtracted statistics shows a successful photon subtraction and the expected shift by one photon number. © 2008 Optical Society of America.

We experimentally demonstrate a heralded source of high-purity two-photon NOON states derived from heralded single-photon sources. © 2008 Optical Society of America.

We demonstrate experimentally the realization of heralded pure photons generation in a birefringent optical fiber. © 2008 Optical Society of America.

We present a direct UV-written integrated photonic circuit with on-chip phase control through a thermo-optic phase shifter. An arbitrary beam splitter and a two-photon NOON state are demonstrated with high visibility interference. © 2010 Optical Society of America.

We discuss recent developments in the characterization of ultrashort optical pulses in the space-time domain and the attosecond regime. These methods may be applied to the study of the dynamics of the field in nonlinear interactions.