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Atomic systems have long provided a useful material platform with unique quantum properties. The efficient light-matter interaction in atomic vapors has led to numerous seminal scientific achievements including accurate and precise metrology and quantum devices. In the last few decades, the field of thin optical elements with miniscule features has been extensively studied demonstrating an unprecedented ability to control photonic degrees of freedom, both linearly and non-linearly, with applications spanning from photography and spatial light modulators to cataract surgery implants. Hybridization of atoms with such thin devices may offer a new material system allowing traditional vapor cells with enhanced functionality. Here, we fabricate and demonstrate chip-scale, quantum diffractive optical elements which map atomic states to the spatial distribution of diffracted light. Two foundational diffractive elements, lamellar gratings and Fresnel lenses, are hybridized with atomic channels containing hot atomic vapors which demonstrate exceptionally strong frequency dependent behaviors. Providing the design tools for chip-scale atomic diffractive optical elements develops a path for a variety of compact thin quantum-optical elements., Comment: 9 Pages, including supplementary

We describe a high-performance, compact optical frequency standard based on a microfabricated Rb vapor cell and a low-noise, external cavity diode laser operating on the Rb two-photon transition at 778 nm. The optical standard achieves an instability of 1.8x10$^{-13}$/$\sqrt{\tau}$ for times less than 100 s and a flicker noise floor of 1x10$^{-14}$ out to 6000 s. At long integration times, the instability is limited by variations in optical probe power and the AC Stark shift. The retrace was measured to 5.7x10$^{-13}$ after 30 hours of dormancy. Such a simple, yet high-performance optical standard could be suitable as an accurate realization of the SI meter or, if coupled with an optical frequency comb, as a compact atomic clock comparable to a hydrogen maser., Comment: 5 pages, 5 figures

We demonstrate a simple stacked scheme that enables absorption imaging through a hole in the surface of a grating magneto-optical trap (GMOT) chip, placed immediately below a micro-fabricated vacuum cell. The imaging scheme is capable of overcoming the reduced optical access and surface scatter that is associated with this chip-scale platform, while further permitting both trapping and imaging of the atoms from a single incident laser beam. The through-hole imaging is used to characterise the impact of the reduced optical overlap volume of the GMOT in the chip-scale cell, with an outlook to an optimised atom number in low volume systems., 5 pages, 3 figures

We evaluate whether the theory of effectuation provides – or could provide – a powerful causal explanation of the process of new venture creation. We do this by conducting an analysis of the principal concepts introduced by effectuation theory. Effectuation theory has become a highly influential cognitive science-based approach to understanding how nascent entrepreneurs start businesses under conditions of uncertainty. But by reducing the process of venture creation to a decision-making logic, effectuation theory pays insufficient regard to the substantial, pervasive and enduring influence of social-structural and cultural contexts on venture creation. Powerful explanations should conceive of venture creation as a sociohistorical process emergent from the interaction of structural, cultural and agential causal powers and must be able to theorise, fallibly, how nascent entrepreneurs form particular firms in particular times and places. We conclude that effectuation’s contribution to entrepreneurship scholarship is more limited than its advocates claim because it can offer only an under-socialised, ahistorical account of venture creation. Failure to theorise adequately the influence of structural and cultural contexts on venture creation implicitly grants nascent entrepreneurs excessive powers of agency.

Chip-scale atomic devices built around micro-fabricated alkali vapor cells are at the forefront of compact metrology and atomic sensors. We demonstrate a micro-fabricated vapor cell that is actively-pumped to ultra-high-vacuum (UHV) to achieve laser cooling. A grating magneto optical trap (GMOT) is incorporated with the 4 mm-thick Si/glass vacuum cell to demonstrate the feasibility of a fully-miniaturized laser cooling platform. A two-step optical excitation process in rubidium is used to overcome surface-scatter limitations to the GMOT imaging. The unambiguous miniaturization and form-customizability made available with micro-fabricated UHV cells provide a promising platform for future compact cold-atom sensors., Comment: 5 pages, 3 figures

Orthogonal control of both degrees of freedom of a Kerr comb soliton allows high-precision atomic spectroscopy and stabilization., Microresonator-based soliton frequency combs, microcombs, have recently emerged to offer low-noise, photonic-chip sources for applications, spanning from timekeeping to optical-frequency synthesis and ranging. Broad optical bandwidth, brightness, coherence, and frequency stability have made frequency combs important to directly probe atoms and molecules, especially in trace gas detection, multiphoton light-atom interactions, and spectroscopy in the extreme ultraviolet. Here, we explore direct microcomb atomic spectroscopy, using a cascaded, two-photon 1529-nm atomic transition in a rubidium micromachined cell. Fine and simultaneous repetition rate and carrier-envelope offset frequency control of the soliton enables direct sub-Doppler and hyperfine spectroscopy. Moreover, the entire set of microcomb modes are stabilized to this atomic transition, yielding absolute optical-frequency fluctuations at the kilohertz level over a few seconds and

This article explores the culture-regulations-gender triad in relation to small and medium enterprises’ (SMEs’) performance. Using a firm-level panel dataset drawn from 27 countries in Central and Eastern Europe and Central Asia between 2005 and 2014, we show that women and men experience and respond differently to regulations. Women take regulations very seriously and as a result, their SMEs see improved performance, whereas men discount the influence of regulations which then depresses the performance of their SMEs. However, when women respond to regulatory enforcers, it erodes the performance of their SMEs, whereas when men engage enforcers, the performance of their SMEs improves. The fact that women and men experience and respond to the same regulations differently—regardless of country effect and whether their SMEs are high- or low-performing businesses—suggests that regulations perpetuate gender biases, thus impacting not only individuals but even the organizations they lead. Our study expands gendered institutions theory by clarifying how regulations diffuse cultural values and influence women and men, as well as their SMEs, differently.

International audience; We show that the light shift in atomic clocks can be suppressed using time variation of the interrogation field intensity. By measuring the clock output at two intensity levels, error signals can be generated that simultaneously stabilize a local oscillator to an atomic transition and correct for the shift of this transition caused by the interrogating optical field. These methods are suitable for optical clocks using one- andtwo-photon transitions, as well as for microwave clocks based on coherent population trapping or direct interrogation. The proposed methods can be widely used both for high-precision scientific instruments and for a wide range of commercial clocks, including chip-scale atomic clocks.

We investigate a solid-state, reversible, alkali-ion battery (AIB) capable of regulating the density of alkali atoms in a vacuum system used for the production of laser-cooled atoms. The cold-atom sample can be used with in-vacuum chronoamperometry as a diagnostic for the voltage-controlled electrochemical reaction that sources or sinks alkali atoms into the vapor. In a combined reaction-diffusion-limited regime, we show that the number of laser-cooled atoms in a magneto-optical trap can be increased both by initially loading the AIB from the vapor for longer, and by using higher voltages across the AIB when atoms are subsequently sourced back into the vapor. The time constants associated with the change in atom number in response to a change in AIB voltage are in the range of 0.5 s - 40 s. The AIB alkali reservoir is demonstrated to survive oxidization during atmospheric exposure, simplifying reservoir loading prior to vacuum implementation as a replacement for traditional resistively-heated dispensers. The AIB capabilities may provide an improved atom number stability in next-generation atomic clocks and sensors, while also facilitating fast loading and increased interrogation times., 7 pages, 5 figures

International audience; Point source atom interferometry, employing optical Raman pulses and a cold atom source, enables measurements of rotation and acceleration in a compact experimental package. This system is uniquely sensitive to rotations in the plane perpendicular to the Raman beamline. Here we discuss our experiment’s sensitivity, stability, systematic errors, and other performance-limiting factors both fundamentaland technical. Our current measurements for the sensitivity to the magnitude and direction of the rotation vector are 0.6 mrad/s and 5 mrad, respectively.

International audience; We present a brief review of the rapidly growing field of autobalanced Ramsey spectroscopy followed by a detailed discussion and review of two novel techniques that were developed and tested in our laboratory: displaced frequency-jump Ramsey spectroscopy and combined error signal spectroscopy. These two techniques are related to, yet different from autobalanced Ramsey spectroscopy. The use of these techniques in a cold-atom clock based on coherent population trapping has reduced instabilities from variations in light-shift parameters by at least one order of magnitude. In each of these techniques the Ramsey sequence adapts to cancel light shifts and drifts.

International audience; In point source atom interferometry (PSI), a cloud of laser-cooled atom expands within a pair of counterpropagatingRaman laser beams and, after a beamsplitter-mirror-beamsplitter Raman pulse sequence, asingle snapshot of the expanded cloud allows simultaneous measurements of one axis of acceleration and two axes of rotation. In PSI, the thermal expansion of the cold-atom cloud, which is undesirable in other atom interferometry methods, is used to establish a position-velocity correlation in the expanded atom cloud. This correlation is employed to map the velocity dependence of the interferometric phaseshift onto a two-dimensional spatial image plane. As a result, the thermal velocity spread of the cloud of laser-cooled atoms facilitates the parallel operation of many atom interferometers, which yields the simultaneous multi-axis sensitivity. PSI provides a new approach to applications of atom interferometers in navigation and space science. For example, the 2D rotation measurement with PSI can be used to find geographic north or to measure the precession of a rotation vector. We have developed a scheme using PSI that is amenable to portable applications and we have demonstrated the measurement of a rotation vector in a plane [1]. We will present our recent results on evaluating the performance and systematic errors in a compact setup and discuss our proposals to address the challenges toward implementing ahigh-precision and portable PSI system.

International audience; Light-induced frequency shifts can be a key limiting contribution to the mid- and long-term frequency instabilities in atomic clocks. In this letter,we demonstrate the experimental implementation of the combined error signal interrogation protocol to a cold-atom clock based on coherent populationtrapping (CPT) and Ramsey spectroscopy. The method uses a single error signal that results from the normalized combination of two errorsignals extracted from two Ramsey sequences of different dark periods. The single combined error signal is used to stabilize the atomic clock frequency.Compared to the standard Ramsey-CPT interrogation, this method reduces the clock frequency sensitivity to light-shift variations bymore than one order of magnitude. This method can be applied in various kinds of Ramsey-based atomic clocks, sensors, and instruments.

International audience; Sophisticated Ramsey-based interrogation protocols using composite laser pulse sequences have been recently proposed to provide next-generation high-precision atomic clocks with a near perfect elimination of frequency shifts induced during the atom-probing field interaction.We propose here a simple alternative approach to the autobalanced Ramsey interrogation protocol and demonstrate its application to a cold-atom microwave clock based on coherent population trapping (CPT). The main originality of the method, based on two consecutive Ramsey sequences with different dark periods, is to sample the central Ramsey fringes with frequency jumps finely adjusted by an additional frequency-displacement concomitant parameter, scaling as the inverse of the dark period. The advantage of this displaced frequency-jump Ramsey method is that the local oscillator (LO) frequency is used as a single physical variable to control both servo loops of the sequence, simplifying its implementation and avoiding noise associated with controlling the LO phase. When tested using a CPT cold-atom clock, the DFJR scheme reduces the sensitivity of the clock frequency to variations of the light shifts by more than an order of magnitude compared with the standard Ramsey interrogation. This simple method can be applied in a wide variety of Ramsey-spectroscopy based applications including frequency metrology with CPT-based and optical atomic clocks, mass spectrometry, and precision spectroscopy.

We have developed a universal method to form the reference signal for the stabilization of arbitrary atomic clocks based on Ramsey spectroscopy. Our approach uses an interrogation scheme of the atomic system with two different Ramsey periods and a specially constructed combined error signal (CES) computed by subtracting two error signals with the appropriate calibration factor. CES spectroscopy allows for perfect elimination of probe-induced light shifts and does not suffer from the effects of relaxation, time-dependent pulse fluctuations and phase-jump modulation errors and other imperfections of the interrogation procedure. The method is simpler than recently developed auto-balanced Ramsey spectroscopy techniques [Ch. Sanner, et al., Phys. Rev. Lett. 120, 053602 (2018); V. I. Yudin, et al., Phys. Rev. Appl. 9, 054034 (2018)], because it uses a single error signal that feeds back on the clock frequency. CES universal technique can be applied to many applications of precision spectroscopy., 12 pages, 6 figures. arXiv admin note: substantial text overlap with arXiv:1712.03365

This article has two objectives: to critique the dominant opportunity discovery and creation literatures and to propose a new, critical realist–inspired analytical framework to theorise the causes, processes and consequences of entrepreneurial action – one that needs no concept of opportunity. We offer three reasons to support our critique of opportunity studies. First, there are important absences, contradictions and inconsistencies in definitions of opportunity in theoretical and empirical work that mean the term cannot signal a clear direction for theorising or empirical research. Our central criticism is that the concept of opportunity cannot refer simultaneously, without contradiction, to a social context offering profit-making prospects, to particular practices and to agents’ subjective beliefs or imagined futures. Second, a new definition of opportunity would perpetuate the conceptual chaos. Third, useful concepts to capture important entrepreneurial processes are readily available, for instance, combining resources, creating new ventures and achieving product sales, which render a concept of opportunity superfluous. Instead, we conceptualise entrepreneurial action as investments in resources intended to create new goods and services for market exchange emergent from the interaction between agential, social-structural and cultural causal powers.

Low thermal-equilibrium nuclear spin polarizations and the need for sophisticated instrumentation render conventional nuclear magnetic resonance (NMR) spectroscopy and imaging (MRI) incompatible with small-scale microfluidic devices. Hyperpolarized 129Xe gas has found use in the study of many materials but has required very large and expensive instrumentation. Recently a microfabricated device with modest instrumentation demonstrated all-optical hyperpolarization and detection of 129Xe gas. This device was limited by 129Xe polarizations less than 1%, 129Xe NMR signals smaller than 20 nT, and transport of hyperpolarized 129Xe over millimeter lengths. Higher polarizations, versatile detection schemes, and flow of 129Xe over larger distances are desirable for wider applications. Here we demonstrate an ultra-sensitive microfabricated platform that achieves 129Xe polarizations reaching 7%, NMR signals exceeding 1 μT, lifetimes up to 6 s, and simultaneous two-mode detection, consisting of a high-sensitivity in situ channel with signal-to-noise of 105 and a lower-sensitivity ex situ detection channel which may be useful in a wider variety of conditions. 129Xe is hyperpolarized and detected in locations more than 1 cm apart. Our versatile device is an optimal platform for microfluidic magnetic resonance in particular, but equally attractive for wider nuclear spin applications benefitting from ultra-sensitive detection, long coherences, and simple instrumentation.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Magnetic resonance in an ensemble of laser-cooled trapped Rb atoms is excited using a micro- cantilever with a magnetic tip. The cantilever is mounted on a multi-layer chip designed to capture, cool, and magnetically transport cold atoms. The coupling is observed by measuring the loss from a magnetic trap as the oscillating cantilever induces Zeeman state transitions in the atoms. Interfacing cold atoms with mechanical devices could enable probing and manipulating atomic spins with nanometer spatial resolution and single-spin sensitivity, leading to new capabilities in quantum computation, quantum simulation, or precision sensing., 5 pages, 4 figures

Purpose – The purpose of this paper is to propose a novel conception of embodied entrepreneurial identity. Prior studies conceptualise identity primarily in terms of narrative or discourse. Critiquing the limited focus on linguistic practices, the authors build on the literature by highlighting the role of the non-linguistic. The implications for researching one particular group – entrepreneurs with impairments – are considered. Design/methodology/approach – Entrepreneurial identity is conceptualised as a unique constellation of concerns emergent from the embodied practices of agents committed to new venture creation and management. This new conception draws principally on the embodiment literature, Archer's identity framework and Goffman's ideas on the presentation of self, impression management and stigma. Findings – The entrepreneurial identity literature is underpinned by a number of problematic assumptions that limit understanding of the meaning, formation and influence of identity on action. The body is often an absent presence; it is presupposed, implicit or under-theorised as an influence on identity, producing a disembodied notion of the entrepreneur. Consequently, entrepreneurs are treated as an homogeneous group in terms of the embodied properties and powers, rather than as uniquely embodied individuals. Studies typically assume an able-bodied, as opposed to a differently abled, agent. Entrepreneurs with impairments are largely invisible in the literature as a result. Originality/value – The approach highlights the role of the body and embodied non-linguistic practices, such as movement, posture, gestures and facial expressions in the formation of identity. Recognising entrepreneurs as differently abled agents, possessing particular embodied properties and powers, is crucial for understanding identity and action.

Optically hyperpolarized $^{129}$Xe gas has become a powerful contrast agent in nuclear magnetic resonance (NMR) spectroscopy and imaging, with applications ranging from studies of the human lung to the targeted detection of biomolecules. Equally attractive is its potential use to enhance the sensitivity of microfluidic NMR experiments, in which small sample volumes yield poor sensitivity. Unfortunately, most $^{129}$Xe polarization systems are large and non-portable. Here we present a microfabricated chip that optically polarizes $^{129}$Xe gas. We have achieved $^{129}$Xe polarizations greater than 0.5$\%$ at flow rates of several microliters per second, compatible with typical microfluidic applications. We employ in situ optical magnetometry to sensitively detect and characterize the $^{129}$Xe polarization at magnetic fields of 1 $\mu$T. We construct the device using standard microfabrication techniques, which will facilitate its integration with existing microfluidic platforms. This device may enable the implementation of highly sensitive $^{129}$Xe NMR in compact, low-cost, portable devices.

High permeability magnetic flux concentrators are used to enhance the sensitivity of an atomic magnetometer operating in the spin-exchange relaxation-free regime. The magnetometer uses a millimeter scale 87Rb vapor cell and either mu-metal or Mn–Zn ferrite flux concentrators. The measured sensitivity gives excellent agreement with calculations of thermal noise from the concentrator material. The mu-metal concentrators allow a sensitivity of 50 fT Hz−1/2, limited by thermal current magnetic noise. The ferrite concentrators are limited by thermal magnetization noise at low frequencies, and reach a sensitivity of 10 fT Hz−1/2 for frequencies above 125 Hz.

Using data from two employer samples, the article develops our understanding of small business employee skill formation and development processes in three main ways. First, it focuses on learning (what employees do) rather than on providing training (what employers do), as it is employee learning which influences individual and organisational performance. Second, it challenges the dominant focus on external training by presenting data on employer enablement of workplace employee learning and their motives for this. The diversity of workplace learning practices and their importance in smaller businesses are highlighted. Third, it situates workplace learning processes firmly within the context of the employment relationship, one in which employers and employees pursue distinctive interests in enabling/participating in learning.

Using data from a longitudinal study of working-class participants on a youth enterprise start-up programme in the United Kingdom, we examine whether programmes aimed at disadvantaged groups enable parents to combine business trading with childcare responsibilities. Business planning and programme selection practices ignored childcare, rendering it a solely private matter, invisible to public scrutiny. Yet this childcare barrier became both a cause and a consequence of business failure. Participants' experiences of combining trading and childcare varied by gender. All mothers and one father had complex strategies for synchronising trading and childcare responsibilities. However, these strategies soon collapsed, contributing to business closure. Most fathers relied on the childrens' mother to organise and conduct continuous care, but this was dependent on fathers becoming breadwinners through profitable trading which was not achieved. There is growing policy recognition of the importance of the childcare barrier to paid work for lower income families and for self-employed women in the United Kingdom. However, despite recent initiatives, severe constraints remain for working-class parents to start and manage a business. Several implications for policy are discussed.

Dynamic nonlinear magneto-optical-rotation signals with frequency- and amplitude-modulated laser light have been observed and investigated with a spherical glass cell of 3-mm diameter containing Cs metal with inner walls coated with paraffin. Intrinsic Zeeman relaxation rates of $\gamma/(2\pi)\approx 20 $Hz and lower have been observed. Favorable prospects of using millimeter-scale coated cells in portable magnetometers and secondary frequency references are discussed., Comment: 7 pages, 9 figures

We develop an analytical theory of dark resonances that accounts for the full atomic-level structure, as well as all field-induced effects such as coherence preparation, optical pumping, ac Stark shifts, and power broadening. The analysis uses a model based on relaxation constants that assumes the total collisional depolarization of the excited state. A good qualitative agreement with experiments for Cs in Ne is obtained., 16 pages; 7 figures; revtex4. Accepted for publication in PRA

The quantum noise limits of a semiconductor laser with dispersive loss are examined theoretically and experimentally. Using optical feedback from Cs vapor as a dispersive loss element we demonstrate almost 6 orders of magnitude reduction in the linewidth, to a 44 Hz level, and 1.9 dB amplitude noise squeezing below the standard quantum noise limit.

Amplitude-squeezed states are generated from a room-temperature semiconductor laser using a combination of pump suppression and dispersive optical feedback. The laser amplitude noise is found to be sensitive to extremely weak feedback levels, of the order of 10-8 of the output power. a reduction of the noise from 2% below the standard quantum limit (SQL) under free-running conditions to 19% below the SQL under optimal feedback conditions is obtained. A single mode theory is presented but is found to be inadequate in explaining the measured dependence of the noise reduction on the feedback power. A multimode theory including asymmetrical cross-mode nonlinear gain is proposed to explain this discrepancy.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The effects of a dispersive loss on the linewidth and chirp of a semiconductor laser are discussed. A van der Pol analysis is used to obtain expressions for linewidth reduction and chirp reduction in an arbitrary optical feedback configuration. Specifically, the use of an atomic cesium vapor as a dispersive loss mechanism is considered. The dominant factor in reducing the linewidth and chirp is shown to be the frequency-dependent phase change from the atomic vapor. However, it is shown that under certain operating conditions the frequency-dependent amplitude changes from the atomic vapor also contribute to the reduction. The results are shown to be in agreement with a detailed rate equation calculation. >