Trapping and optically interfacing laser-cooled neutral atoms are essential requirements for their use in advanced quantum technologies. Here we simultaneously realize both of these tasks with cesium atoms interacting with a multicolor evanescent field surrounding an optical nanofiber. The atoms are localized in a one-dimensional optical lattice about 200 nm above the nanofiber surface and can be efficiently interrogated with a resonant light field sent through the nanofiber. Our technique opens the route towards the direct integration of laser-cooled atomic ensembles within fiber networks, an important prerequisite for large scale quantum communication schemes. Moreover, it is ideally suited to the realization of hybrid quantum systems that combine atoms with, e.g., solid state quantum devices.

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We experimentally study the ground state coherence properties of cesium atoms in a nanofiberbased two-color dipole trap, localized ∼ 200 nm away from the fiber surface. Using microwave radiation to coherently drive the clock transition, we record Ramsey fringes as well as spin echo signals and infer a reversible dephasing time of T * 2 = 0.6 ms and an irreversible dephasing time of T 2 = 3.7 ms. By modeling the signals, we find that, for our experimental parameters, T * 2 and T 2 are limited by the finite initial temperature of the atomic ensemble and the heating rate, respectively. Our results represent a fundamental step towards establishing nanofiber-based traps for cold atoms as a building block in an optical fiber quantum network.PACS numbers: 42.50. Ct, 37.10.Gh, 37.10.Jk, 42.50.Ex Over the past years, hybrid quantum systems have attracted considerable attention [1]. In the specific case of light-matter quantum interfaces [2-4], they combine the advantages of photons for transmitting quantum information and of long-coherence-time systems, such as dopant ions in crystals, NV centers, quantum dots, single trapped neutral atoms and ions, and atomic ensembles, for storing and processing quantum information and for realizing long-distance quantum communication [5]. In the context of quantum networks [6], it would be highly desirable to connect these matter-based storage and processing units via optical fiber links. A promising approach towards the realization of such fiberbased quantum interfaces consists in coupling cold neutral atoms to photonic crystal fibers [7][8][9]. Another technique with high potential involves trapping and interfacing cold atoms in the evanescent field surrounding optical nanofibers. Using the optical dipole force exerted by a blue-and a red-detuned nanofiber-guided light field [10,11], two-color traps have been demonstrated experimentally with laser-cooled cesium atoms [12,13].In order to implement quantum protocols with atoms coupled to nanophotonic devices, good coherence properties are a prerequisite but cannot be taken for granted: various effects, like Johnson noise [14] or patch potentials [15] may occur and hamper long coherence times [16]. When coupling to optical near-fields, this is all the more critical because of the small atom-surface distance of typically a few hundred nanometers. Here, using Ramsey interferometry as well as spin-echo techniques, we measure, to the best of our knowledge for the first time, the reversible and irreversible dephasing times of atoms in such an environment. Specifically, we experimentally characterize and model the ground state coherence of the clock transition of cesium atoms stored in the nanofiber-based two-color trap realized in [12]. Remarkably, the inferred coherence times extend up to milliseconds.The experimental set-up is sketched in Fig. 1a and is a. Sketch of the experimental set-up including the tapered optical fiber, the trapping, probe and push-out laser fields, the microwave antenna, and the single-photon counter (SPCM). b. ...

We dispersively interface an ensemble of one thousand atoms trapped in the evanescent field surrounding a tapered optical nanofiber. This method relies on the azimuthally-asymmetric coupling of the ensemble with the evanescent field of an off-resonant probe beam, transmitted through the nanofiber. The resulting birefringence and dispersion are significant; we observe a phase shift per atom of ∼ 1 mrad at a detuning of six times the natural linewidth, corresponding to an effective resonant optical density per atom of 0.027. Moreover, we utilize this strong dispersion to nondestructively determine the number of atoms.PACS numbers: 42.50. Ct, 37.10.Gh, 37.10.Jk We have recently demonstrated a new technique for trapping and optically interfacing cold atoms [1]. Our method employs one-dimensional arrays of laser-cooled atoms trapped in a two-color evanescent field surrounding an optical nanofiber. The resulting atomic ensemble is both well-isolated from perturbations by the environment and efficiently coupled to a fiber-guided probe field. This makes our system a prime candidate for interfacing and manipulating trapped atoms with light.In [1], the detection of cesium atoms was achieved by monitoring the transmission of resonant probe light through the nanofiber. This probe light couples efficiently to the atoms via its evanescent field resulting in an absorbance per atom of the order of one percent. This strong absorbance also implies that there is a significant phase shift of the probe light in the dispersive regime. In this paper, we present experimental evidence of this phase shift and show that it leads to a frequencydependent birefringence that acts on the polarization state of the probe light propagating through the fiber.Being based on dispersive detection, our method has significant advantages over absorption or fluorescencebased techniques [2]. As an example, its signal-to-noise ratio is superior in the case of high optical depth when assuming shot-noise-limited detection [3]. Conceptually, it is similar to other dispersive detection schemes for atoms and molecules such as interferometry [4,5], frequency modulation spectroscopy [6], or phase-contrast imaging [7].In all these approaches, the phase shift induced by the atomic medium on the probe beam is compared to the phase of a reference beam via interference. In the case of atoms trapped using a nanofiber, this can be accomplished by interfering two orthogonal polarization modes, which couple unequally to the atomic ensemble. The polarization state of the output light thus enables one to infer the phase shift caused by the atoms. Figure 1 shows a schematic of the experimental setup. The atoms are trapped in two one-dimensional arrays FIG. 1. Schematic of the setup: An off-resonant laser beam is coupled into the nanofiber to probe the cesium atoms, which are trapped in the evanescent field of the nanofiber forming two one-dimensional arrays above and below the fiber (zoomed inset). A Stokes measurement is performed on the outgoing probe beam using a quart...

Ideally, the DIBH technique should be offered to all patients with left-sided breast cancer. However, highest benefits are expected for patients with a favourable tumour prognosis, high mean heart dose or high baseline IHD risk, independent of their age.

We present experimental techniques and results related to the optimization and characterization of our nanofiberbased atom trap [Vetsch et al., Phys. Rev. Lett. 104, 203603 (2010)]. The atoms are confined in an optical lattice which is created using a two-color evanescent field surrounding the optical nanofiber. For this purpose, the polarization state of the trapping light fields has to be properly adjusted. We demonstrate that this can be accomplished by analyzing the light scattered by the nanofiber. Furthermore, we show that loading the nanofiber trap from a magneto-optical trap leads to sub-Doppler temperatures of the trapped atomic ensemble and yields a sub-Poissonian distribution of the number of trapped atoms per trapping site.Index Terms-Nanophotonics, optical nanofibers, laser cooling and trapping of atoms. 2012 c IEEE, see http://www.ieee.org for copyright policy IEEE

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Although the organ preservation strategy by breast-conserving surgery (BCS) followed by radiation therapy (BCT) has revolutionized the treatment approach of early stage breast cancer (BC), the choice between treatment options in this setting can still vary according to patient preferences. The aim of the present study was to compare the oncological outcome of mastectomy versus breast-conserving therapy in patients treated in a modern clinical setting outside of clinical trials. 7565 women diagnosed with early invasive BC (pT1/2pN0/1) between 1998 and 2014 were included in this study (median follow-up: 95.2 months). In order to reduce selection bias and confounding, a subgroup analysis of a matched 1:1 case-control cohort consisting of 1802 patients was performed (median follow-up 109.4 months). After adjusting for age, tumor characteristics and therapies, multivariable analysis for local recurrence-free survival identified BCT as an independent predictor for improved local control (hazard ratio [HR]:1.517; 95%confidence interval:1.092–2.108, p = 0.013) as compared to mastectomy alone in the matched cohort. Ten-year cumulative incidence (CI) of lymph node recurrences was 2.0% following BCT, compared to 5.8% in patients receiving mastectomy (p < 0.001). Similarly, 10-year distant-metastasis-free survival (89.4% vs. 85.5%, p = 0.013) was impaired in patients undergoing mastectomy alone. This translated into improved survival in patients treated with BCT (10-year overall survival (OS) estimates 85.3% vs. 79.3%, p < 0.001), which was also significant on multivariable analysis (p = 0.011). In conclusion, the present study showed that patients treated with BCS followed by radiotherapy had an improved outcome compared to radical mastectomy alone. Specifically, local control, distant control, and overall survival were significantly better using the conservative approach. Thus, as a result of the present study, physicians should encourage patients to receive BCS with radiotherapy rather than mastectomy, whenever it is medically feasible and appropriate.