The speckle pattern produced when a laser illuminates a random medium can, with appropriate analysis, be used to uniquely identify the wavelength of the illuminating source. We have demonstrated that principal component analysis can be used as a very sensitive probe of the speckle pattern produced by random prisms [1] and integrating spheres [2]. However, to date, the state-of-the-art realisations of speckle spectrometers have been based on the use of multi-mode fibres as the scattering medium [3] and on transmission matrix analysis approaches, achieving a compact and stable device with picometre resolution. Here, we show that the speckle pattern produced by propagation through a metre-long step-index multi-mode optical fibre can be analysed with principal component analysis to achieve a femtometre-precision wavemeter, and present progress in the measurement of complete spectra, which demonstrates the applicability of our approach to many existing experiments. Moreover, we demonstrate that the speckle wavemeter can be used as part of a feedback loop to stabilise lasers to a fractional stability of 10-9. With the freedom to lock the laser at any user-desired frequency and a robust, compact setup, the method holds promise for the new generation of portable cold atom experiments currently being developed for quantum technology applications. [1] M Mazilu, et al. Opt Lett 39, 96 (2014) [2] N K Metzger, et al. Nat. Commun. 8, 15610 (2017) [3] H Cao, J. Opt. 19, 060402 (2017)
The speckle pattern produced when a laser illuminates a random medium can, with appropriate analysis, be used to uniquely identify the wavelength of the illuminating source. We have demonstrated that principal component analysis can be used as a very sensitive probe of the speckle pattern produced by random prisms [1] and integrating spheres [2]. However, to date, the state-of-the-art realisations of speckle spectrometers have been based on the use of multi-mode fibres as the scattering medium [3] and on transmission matrix analysis approaches, achieving a compact and stable device with picometre resolution. Here, we show that the speckle pattern produced by propagation through a metre-long step-index multi-mode optical fibre can be analysed with principal component analysis to achieve a femtometre-precision wavemeter, and present progress in the measurement of complete spectra, which demonstrates the applicability of our approach to many existing experiments. Moreover, we demonstrate that the speckle wavemeter can be used as part of a feedback loop to stabilise lasers to a fractional stability of 10-9. With the freedom to lock the laser at any user-desired frequency and a robust, compact setup, the method holds promise for the new generation of portable cold atom experiments currently being developed for quantum technology applications. [1] M Mazilu, et al. Opt Lett 39, 96 (2014) [2] N K Metzger, et al. Nat. Commun. 8, 15610 (2017) [3] H Cao, J. Opt. 19, 060402 (2017)
Laser speckle, the granular intensity pattern arising from random optical interference, provides a high-dimensional encoding of spectral information that can be exploited for precision metrology. Speckle-based spectrometers have advanced rapidly owing to their compact footprint, mechanical robustness and alignment agnostic nature, yet their spectral resolution has remained limited to the picometre scale. In this work, we break this limit by employing an integrating sphere as a multiply scattering cavity with access to a high range of path lengths to enhance spectral sensitivity. At 780nm, the resulting device achieves a resolution of 6fm, corresponding to a resolving power of 1.3×108, representing an approximately 80-fold improvement over previous implementations. This ultra-high resolution enables clear discrimination of laser sidebands generated by an electro-optical modulator, with extracted sideband powers agreeing with expected values to within 1%. It further permits the first direct speckle-based measurement of the hyperfine structure of the D2 transition in 85Rb, with transmission spectra differing by no more than 3.6% from independent wavemeter-referenced measurements. These results establish speckle as a new platform for ultra-high precision spectroscopy, radio-frequency spectrometry, and microwave photonics.
Fiber laser sources from visible to near-infrared wavelengths have driven innovative developments, impacting various domains such as telecommunications, biology, and medicine. The development of such fiber laser relies on the accurate knowledge of both optical properties as chromatic dispersion and material properties. On the other hand, quantum metrology is one of the promising field enabled by quantum technologies. It allows to get precise results compare to classical methods when measuring physical properties. A very common approach is to inject non classical states of light in interferometers to increase accuracy as well as sensitivity. Recently, this scheme has been used for detecting gravitational waves for example [1]. During the conference, we show how we take advantage of these capabilities to gather optical fiber photonic engineering with quantum optics. More specifically, we aim at presenting two quantum-based method for (i) high-accuracy (10-5) and dispersion-free measurement of refractive index difference and (ii) chromatic dispersion measurement based on the concept of quantum white-light interferometry that allows absolute measurement of chromatic dispersion with ~2.5 times improved accuracies compared to state-of-the-art realizations at telecom wavelengths. [1] B. P. Abbott et. al., ”Observation of Gravitational Waves from a Binary Black Hole Merger”, Phys. Rev. Lett., 116, 061102 (2016)
In this presentation, we will introduce the quantum equivalent of white-light interferometry. However, instead of a classical light source with thermal or poissonian statistics, we use energy-time entangled photon pairs. This provides one with several important advantages, which are highly relevant for high-accuracy measurements of chromatic dispersion: 1.) The interferometer does not have to be balanced, which improves the set-up time, especially when comparing different fibres. 2.) Two data fitting parameters are cancelling out, which reduces systematic errors significantly. 3.) The wavelength at which dispersion is measured is not extracted from the data, but is rather inferred with arbitrary precision using a wavemeter or an atomic reference. 4.) Twice as many interference fringes are observed for the same spectral bandwidth, allowing to measure dispersion in standard telecom fibres down to about 3 cm with a 140 nm bandwidth source. After introducing the concept and highlighting the quantum advantages, we will demonstrate the performance of the quantum approach by comparing it to the best state-of-the-art approaches. Statistical analysis is performed by 2 times 100 measurements using either technique. In terms of precision, the quantum (classical) approach achieves a 1-sigmal precision of 21 fs/nm/km (51 fs/nm/km). In addition, the classical approach presents a systematic error of 12 fs/nm/km, which is unlikely to occur using the quantum approach, as the related fitting parameters cancel out automatically. In summary, we believe that combining fundamental and conceptual advantages enabled by quantum optics is a promising approach for the future development of applications requiring precise and accurate measurements.
Our ability to manipulate the coherence properties of light has been at the heart of many of the most important scientific and technological innovations of this century. There can hardly be a home in this country that does not possess a laser in the form of a compact disc player or a CDROM. When we talk on the phone, or send messages on the Internet, there is a high probability that our message will be encoded by a laser into pulses of light to be passed through optical fibres. In the last few years physicists have been discovering that it is possible to control the coherence properties of atoms, and are now developing tools analogous to those which have been developed to take advantage of the coherence properties of light. In the next decade we can look forward to seeing the application of lasers, fibres, mirrors and waveguides for atoms. Already we have been able to construct interferometry experiments using beams of atoms and these have proved to be extremely sensitive measurement devices, allowing us to test physical theories and measure fundamental constants to a level of precision not previously possible. Will these developing technologies ever be as ubiquitous as their optical forebears? In this paper we discuss the anticipated uses of this technology for both fundamental science and industrial applications. Starting from an explanation of the meaning of coherence and a comparison of the properties of photons and atoms, we describe the development of the science of atom optics. The tortuous route towards the great achievement of producing a Bose–Einstein condensate is described, and we explain why this is the most important step towards a laser–like source of atoms. Numerous other optical elements for atoms have been built or are on the drawing board, and we describe how these may be used to manipulate atoms with a precision that has never before been achieved, and look ahead to what we can learn about physics using these tools and at how they can be put to practical use.
We have developed a nozzle source that delivers a continuous beam of atomic helium or molecular hydrogen having a high degree of transverse coherence and with adequate optical brightness to enable new kinds of experiments. Using this source we have measured single slit diffraction patterns and the first ever speckle-diffraction patterns using atomic and molecular de Broglie waves. Our results suggest fruitful application of coherent matter beams in dynamic scattering and diffractive imaging at short wavelength and with extreme surface sensitivity.
The exploitation of quantum mechanics has the potential to solve important challenges and \nintroduce novel technologies enabling, among others, powerful computation (which can solve \ncertain problems exponentially faster than classical computers), perfectly secure communications, \nas well as sensing and imaging with precision and resolutions not achievable by classical means. \nIn order to make use of the unique properties of quantum physics, experimental platforms \nthat provide access to, and allow the control of quantum states, need to be developed. In \nparticular, quantum systems composed of multiple parties are required, where each party is in a \ncoherent superposition of states, and where multiples of such parties are in a coherent \nsuperposition with each other (e.g. being entangled). Additionally, in order to make use of such \nentangled quantum systems, it is required that each individual party can be coherently controlled \nand measured. The usability and available quantum resources of the entangled system is related \nto its size, which is proportional to the number of entangled parties, as well as the dimensionality \nof the superposition each party is in. For this reason, there is a imminent demand to achieve, \ninvestigate, and improve the generation and control of large quantum systems, comprised of as \nmany entangled parties as possible, where each party is in an ideally high-dimensional \nsuperposition. \nMany quantum platforms are currently subject to extensive research, such as trapped ions, \nsuperconducting circuits, defect centers in solid-state crystals, mechanical oscillators, and optical \nquantum states (i.e. photons). While all platforms provide distinct advantages (as well as \nchallenges), optical photon states are of particular interest, because they can interact with other \nquantum systems, and can be transmitted over long distances while preserving their quantum \ncoherence without the need for extensive shielding. A large variety of sources for optical \nquantum states has been demonstrated, however most such implementations suffer from high \ncomplexity, ultimately limiting their scalability. Integrated photonics has recently become a \nleading platform for the compact, cost-efficient, and stable generation and processing of optical \nquantum states. However, to date, integrated quantum sources have only been able to generate \nphoton pairs, which operated on single channels, and single polarization modes. Furthermore, in \nthe few realizations of on-chip entanglement, they were limited to two entangled parties, where \neach party was in a two-dimensional superposition. These limitations of current integrated photon sources arise in large part from the concepts currently exploited to generate and control these \nstates. In particular, path-entangled sources are the most commonly used, but increasing the \nquantum state complexity requires a significant, and very challenging, increase in device \ncomplexity. There is therefore an urgent need to develop new concepts that can achieve the onchip \ngeneration of large and complex photon states without increasing source complexity, while \nstill enabling coherent quantum state control and detection. \nIn this work, we aim to address these limitations by making use of multiple frequency and \ntemporal modes within a single spatial waveguide mode (therefore readily compatible with \nstandard optical fibers) of an on-chip microring resonator. This approach is in contrast to more \ncommonly used techniques relying on path entanglement, which exploits multiple spatial modes \nand generates entanglement by means of complex waveguide structures. Working within a single \nspatial mode, we achieve the first demonstration of pure heralded single photons and entangled \nphoton pairs, which are emitted on multiple frequency modes from a single source. We then \ndemonstrate the first generation of multi-photon entangled quantum states on a photonic chip. \nFinally, by making use of the spectral multi-mode nature of optical frequency combs, we achieve \nthe generation of photon pairs in a coherent superposition of multiple frequency modes, \nrepresenting the first generation of high-dimensional entangled states on a photonic chip. \nOur work represents a significant step forward in the generation of complex quantum \nstates on a photonic chip and in a single spatial mode compatible with standard optical fibers. In \naddition, we demonstrated coherent quantum state control and manipulation for all generated \nstates by means of standard telecommunications components, which could in the future be also \nintegrated on single, monolithic chip. Our results indicate that the exploitation of integrated \noptical frequency comb sources for the generation of optical quantum states can provide a \nscalable and practical platform for quantum technologies.