We introduce spectrally-resolved quantum white-light interferometry exploiting energy-time entangled two-photon N00N-states for chromatic dispersion measurements. Compared to state-of-the-art approaches, we demonstrate 2.6 times enhanced precision, combined with absolute parameter determination.
White-light interferometry is one of today's most precise tools for determining the properties of optical materials. Its achievable precision and accuracy are typically limited by systematic errors due to a high number of interdependent data-fitting parameters. Here, we introduce spectrally resolved quantum white-light interferometry as a novel tool for optical property measurements, notably, chromatic dispersion in optical fibres. By exploiting both spectral and photon-number correlations of energy-time entangled photon pairs, the number of fitting parameters is significantly reduced, which eliminates systematic errors and leads to an absolute determination of the material parameter. By comparing the quantum method to state-of-the-art approaches, we demonstrate the quantum advantage of 2.4 times better measurement precision, despite requiring 62 times fewer photons. The improved results are due to conceptual advantages enabled by quantum optics, which are likely to define new standards in experimental methods for characterising optical materials.
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.
Quantum optical metrology enables phase sensitive measurements with a resolution beyond the classical Heisenberg limit. Here, we demonstrate a novel quantum metrology scheme for entanglement-enhanced chromatic dispersion (CD) measurements in short fibres and samples. Besides the expected doubled phase sensitivity, exploiting energy-time and path entanglement allows eliminating the major inconveniences of classical measurements based on white light interferometry (WLI). Our experimental procedure is significantly faster compared to the classical counterpart, and entanglement permits to further exploit a more simplified fitting function. Using these advantages, we measure CD in a 1 m long standard telecom fibre (Corning SMF28e) with an accuracy on top of the state-of-the-art, i.e. with an 1.7 times improved accuracy compared to the classical strategy.
Since the first proof-of-principle experiments 25 years ago, quantum metrology has matured from fundamental concepts to versatile and powerful tools in a large variety of research branches, such as gravitational-wave detection, atomic clocks, plasmonic sensing, and magnetometry. At the same time, two-photon interferometry, which underpins the possibility of entanglement to probe optical materials with unprecedented levels of precision and accuracy, holds the promise to stand at the heart of innovative functional quantum sensing systems. We report a quantum based method for measuring the frequency dependence of the velocity in a transparent medium, i.e., chromatic dispersion (CD). This technique, using energy-time-entangled photons, allows straightforward access to CD value from the visibility of two-photon fringes recorded in a free-evolution regime. In addition, our quantum approach features all the advantages of classical measurement techniques, i.e., flexibility and accuracy, all in a plug-and-play system.
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)