Systematic optimization of laser cooling of dysprosium
Florian Mühlbauer, Niels Petersen, Carina Baumgärtner, Lena Maske & Patrick Windpassinger
Abstract
We report on an apparatus for cooling and trapping of neutral dysprosium. We characterize and optimize the performance of our Zeeman slower and 2D molasses cooling of the atomic beam by means of Doppler spectroscopy on a 136 kHz broad transition at 626 nm. Furthermore, we demonstrate the characterization and optimization procedure for the loading phase of a magneto-optical trap (MOT) by increasing the effective laser linewidth by sideband modulation. After optimization of the MOT compression phase, we cool and trap up to 109 atoms within 3 seconds in the MOT at temperatures of 9 µK and phase space densities of 1.7·10−5, which constitutes an ideal starting point for loading the atoms into an optical dipole trap and for subsequent forced evaporative cooling.
Alexandre Parriaux, Kamal Hammani, Christophe Thomazo, Olivier Musset, and Guy Millot
Abstract
We demonstrate the use of dual-comb spectroscopy for isotope ratio measurements. We show that the analysis spectral range of a free-running near-infrared dual-comb spectrometer can be extended to the midinfrared by difference frequency generation to target specific spectral regions suitable for such measurements and especially the relative isotopic ratio δ13C. The measurements performed present very good repeatability over several days with a standard deviation below 2‰ for a recording time of a few tens of seconds, and the results are compatible with measurements obtained using an isotope ratio mass spectrometer. Our setup also shows the possibility to target several chemical species without any major modification, which can be used to measure other isotopic ratios. Further improvements could decrease the uncertainties of the measurements, and the spectrometer could thus compete with isotope ratio spectrometers currently available on the market.
N. Bruno, E. Zambrini Cruzeiro, A. Martin, R.T. Thew
Abstract
We report the realization of a fibred polarization entangled photon-pair source at 1560 nm based on a type-II nonlinear interaction and working in the picosecond regime. By taking advantage of a set of fibre filters, we deterministically separate the photons and project them into wavelength separable states. A standard entanglement measurement with a net interference visibility close to 1 proves the relevance of our approach as an enabling technology for entanglement-based quantum communication.
Two-photon microscopy with a frequency-doubled fully fusion-spliced fiber laser at 1840 nm
C.-H. Hage, J.-T. Gomes, S. M. Bardet, G. Granger, M. Jossent, L. Lavoute, D. Gaponov, and S. Fevrier
Abstract
We introduce a fiber-based laser system providing 130 fs pulses with 3.5 nJ energy at 920 nm at a 43 MHz repetition rate and illustrate the potential of the source for two-photon excited fluorescence microscopy of living mouse brain. The laser source is based on frequency-doubling high-energy solitons generated and frequency-shifted to 1840 nm in large mode area fibers. This simple laser system could unleash the potential of two-photon microscopy techniques in the biology laboratory where green fluorescent proteins with two-photon absorption spectrum peaking around 920 nm are routinely used.
GHz-pulsed source of entangled photons for reconfigurable quantum networks
Meritxell Cabrejo-Ponce, Christopher Spiess, André Luiz Marques Muniz, Philippe Ancsi and Fabian Steinlechner
Abstract
Entanglement is a universal resource in quantum networks, yet entangled photon sources are typically custom-made for a specific use case. Versatility, both in terms of state modulation and tunability of the temporal properties of the photons, is the key to flexible network architectures and cryptographic primitives that go beyond quantum key distribution. Here, we report on a flexible source design that produces high-quality entanglement in continuous-wave and GHz-rate-pulsed operation modes. Utilizing off-the-shelf optical components, our approach uses a fiber-based Sagnac loop to generate polarization-entangled photons at telecom wavelength with high efficiency and fidelities above 0.99. Phase modulation up to GHz before entangled state generation is also possible for fast entangled state switching. We show phase modulation at 100 MHz with an average fidelity of 0.95. Furthermore, the source 60 nm spectral bandwidth is entirely compatible with fully reconfigurable wavelength-multiplexed quantum networks.
Ultra-low vibration closed-cycle cryogenic surface-electrode ion trap apparatus
Timko Dubielzig, Sebastian Halama, Henning Hahn, Giorgio Zarantonello, Malte Niemann, Amado Bautista-Salvador, Christian Ospelkaus
Abstract
We describe the design, commissioning and operation of an ultra-low-vibration closed-cycle cryogenic ion trap apparatus. One hundred lines for low-frequency signals and eight microwave / radio frequency coaxial feed lines offer the possibility of implementing a small-scale ion-trap quantum processor or simulator. With all supply cables attached, more than 1.3 W of cooling power at 5 K is still available for absorbing energy from electrical pulses introduced to control ions. The trap itself is isolated from vibrations induced by the cold head using a helium exchange gas interface. The performance of the vibration isolation system has been characterized using a Michelson interferometer, finding residual vibration amplitudes on the order of 10 nm rms. Trapping of 9Be+ ions has been demonstrated using a combination of laser ablation and photoionization.
Nonlinear optical imaging by detection with optical parametric amplification (invited paper)
Yi Sun, Haohua Tu and Stephen A. Boppart
Abstract
Nonlinear optical imaging is a versatile tool that has been proven to be exceptionally useful in various research fields. However, due to the use of photomultiplier tubes (PMTs), the wide application of nonlinear optical imaging is limited by the incapability of imaging under ambient light. In this paper, we propose and demonstrate a new optical imaging detection method based on optical parametric amplification (OPA). As a nonlinear optical process, OPA intrinsically rejects ambient light photons by coherence gating. Periodical poled lithium niobate (PPLN) crystals are used in this study as the media for OPA. Compared to bulk nonlinear optical crystals, PPLN crystals support the generation of OPA signal with lower pump power. Therefore, this characteristic of PPLN crystals is particularly beneficial when using high repetition- rate lasers, which facilitate high-speed optical signal detection, such as in spectroscopy and imaging. A PPLN-based OPA system was built to amplify the emitted imaging signal from second harmonic generation (SHG) and coherent anti-Stokes Raman scattering (CARS) microscopy imaging, and the amplified optical signal was strong enough to be detected by a biased photodiode under ordinary room light conditions. With OPA detection, ambient light- on SHG and CARS imaging becomes possible, and achieves a similar result as PMT detection under strictly dark environments. These results demonstrate that OPA can be used as a substitute for PMTs in nonlinear optical imaging to adapt it to various applications with complex lighting conditions.
Ultratunable Quantum Frequency Conversion in Photonic Crystal Fiber
K. A. G. Bonsma-Fisher, P. J. Bustard, C. Parry, T. A. Wright, D. G. England, B. J. Sussman, and P. J. Mosley
Abstract
Quantum frequency conversion of single photons between wavelength bands is a key enabler to realizing widespread quantum networks. We demonstrate the quantum frequency conversion of a heralded 1551 nm photon to any wavelength within an ultrabroad (1226–1408 nm) range in a group-velocity-symmetric photonic crystal fiber, covering over 150 independent frequency bins. The target wavelength is controlled by tuning only a single pump laser wavelength. We find internal, and total, conversion efficiencies of 12(1)% and 1.4(2)%, respectively. For the case of converting 1551 to 1300 nm we measure a heralded g(2)(0)=0.25(6) for converted light from an input with g(2)(0)=0.034(8). We expect that this photonic crystal fiber can be used for myriad quantum networking tasks.
Spatial Properties of Entangled Two-Photon Absorption
D. Tabakaev, A. Djorović, L. La Volpe, G. Gaulier, S. Ghosh, L. Bonacina, J.-P. Wolf, H. Zbinden, and R. T. Thew
Abstract
We experimentally study entangled two-photon absorption in rhodamine 6G as a function of the spatial properties of a high flux of broadband entangled photon pairs. We first demonstrate a key signature dependence of the entangled two-photon absorption rate on the type of entangled pair flux attenuation: linear, when the laser pump power is attenuated, and quadratic, when the pair flux itself experiences linear loss. We then perform a fluorescence-based Z-scan measurement to study the influence of beam waist size on the entangled two-photon absorption process and compare this to classical single- and two-photon absorption processes. We demonstrate that the entangled two-photon absorption shares a beam waist dependence similar to that of classical two-photon absorption. This result presents an additional argument for the wide range of contrasting values of quoted entangled two-photon absorption cross sections of dyes in literature.
D. Tabakaev, M. Montagnese, G. Haack, L. Bonacina, J.-P. Wolf, H. Zbinden, and R. T. Thew
Abstract
Nonlinear spectroscopy and microscopy techniques are ubiquitous in a wide range of applications across physics and biology. However, these usually rely on high-powered pulsed laser systems. A promising alternative is to exploit entangled two-photon absorption (ETPA), which can lead to tens of orders of magnitude lower incident fluxes than in conventional two-photon absorption schemes. However, the role of different entangled degrees of freedom in ETPA was unclear following recent experimental studies, when compared to earlier theoretical works. Here, we first demonstrate a linear dependence of the ETPA rate with the photon-pair rate, a clear signature of ETPA, and estimate the values for the concentration-dependent ETPA cross section for Rhodamine 6G. We then investigate the signature of energy-time entanglement and polarization dependence in the ETPA fluorescence rate and demonstrate a strong dependence of the signal on the interphoton delay that reflects the coherence time of the entangled two-photon wave packet.
