Remarkable progress can be observed in recent years in the controlled emission, guiding, and detection of coherent, free electrons. Those methods were applied in matter wave interferometers leading to high phase sensitivities and precise sensor technologies for dephasing influences such as mechanical vibrations or electromagnetic frequencies. However, the previous devices have been large laboratory setups. For future sensor applications or tests of the coherence properties of an electron source, small, portable interferometers are required. Here, we demonstrate a compact biprism electron interferometer that can be used for mobile applications. The design was optimized for small dimensions by beam path simulations. The interferometer has a length between the tip and the superposition plane before magnification of only 47 mm and provides electron interference patterns with a contrast up to 42.7%. The detection of two dephasing frequencies at 50 and 150 Hz was demonstrated applying second order correlation and Fourier analysis of the interference data.
Remarkable progress can be observed in recent years in the controlled emission, guiding, and detection of coherent, free electrons. Those methods were applied in matter wave interferometers leading to high phase sensitivities and precise sensor technologies for dephasing influences such as mechanical vibrations or electromagnetic frequencies. However, the previous devices have been large laboratory setups. For future sensor applications or tests of the coherence properties of an electron source, small, portable interferometers are required. Here, we demonstrate a compact biprism electron interferometer that can be used for mobile applications. The design was optimized for small dimensions by beam path simulations. The interferometer has a length between the tip and the superposition plane before magnification of only 47 mm and provides electron interference patterns with a contrast up to 42.7%. The detection of two dephasing frequencies at 50 and 150 Hz was demonstrated applying second order correlation and Fourier analysis of the interference data.
Matter-wave interferometry is a highly sensitive tool to measure small perturbations in a quantum system.This property allows the creation of precision sensors for dephasing mechanisms such as mechanical vibrations.They are a challenge for phase measurements under perturbing conditions that cannot be perfectly decoupled from the interferometer, e.g.for mobile interferometric devices or vibrations with a broad frequency range.Here, we demonstrate a method based on second-order correlation theory in combination with Fourier analysis, to use an electron interferometer as a sensor that precisely characterizes the mechanical vibration spectrum of the interferometer.Using the high spatial and temporal single-particle resolution of a delay line detector, the data allows to reveal the original contrast and spatial periodicity of the interference pattern from 'washed-out' matter-wave interferograms that have been vibrationally disturbed in the frequency region between 100 and 1000 Hz.Other than with electromagnetic dephasing, due to excitations of higher harmonics and additional frequencies induced from the environment, the parts in the setup oscillate with frequencies that can be different to the applied ones.The developed numerical search algorithm is capable to determine those unknown oscillations and corresponding amplitudes.The technique can identify vibrational dephasing and decrease damping and shielding requirements in electron, ion, neutron, atom and molecule interferometers that generate a spatial fringe pattern on the detector plane.
A general challenge in various quantum experiments and applications is to develop suitable sources for coherent particles. In particular, recent progress in microscopy, interferometry, metrology, decoherence measurements and chip based applications rely on intensive, tunable, coherent sources for free low energy electron matter waves. In most cases, the electrons get field emitted from a metal nanotip where its radius and geometry towards a counter electrode determines the field distribution and the emission voltage. A higher emission is often connected to faster electrons with smaller de Broglie wavelengths, requiring larger pattern magnification after matter wave diffraction or interferometry. This can be prevented with a well-known setup consisting of two counter electrodes that allow independent setting of the beam intensity and velocity. However, it needs to be tested if the coherent properties of such a source are preserved after the acceleration and deceleration of the electrons. Here, we study the coherence of the beam in a biprism interferometer with a single atom tip electron field emitter if the particle velocity and wavelength varies after emission. With a Wien filter measurement and a contrast correlation analysis we demonstrate that the intensity of the source at a certain particle wavelength can be enhanced up to a factor of 33 without changing the transverse and longitudinal coherence of the electron beam. In addition, the energy width of the single atom tip emitter was measured to be 377 meV, corresponding to a longitudinal coherence length of 82 nm. The design has potential applications in interferometry, microscopy and sensor technology
A general challenge in various quantum experiments and applications is to develop suitable sources for coherent particles. In particular, recent progress in microscopy, interferometry, metrology, decoherence measurements, and chip-based applications rely on intensive, tunable, coherent sources for free low-energy electron-matter waves. In most cases, the electrons get field emitted from a metal nanotip, where its radius and geometry toward a counter electrode determines the field distribution and the emission voltage. A higher emission is often connected to faster electrons with smaller de Broglie wavelengths, requiring larger pattern magnification after matter-wave diffraction or interferometry. This can be prevented with a well-known setup consisting of two counter electrodes that allow independent setting of the beam intensity and velocity. However, it needs to be tested if the coherent properties of such a source are preserved after the acceleration and deceleration of the electrons. Here, we study the coherence of the beam in a biprism interferometer with a single atom tip electron field emitter if the particle velocity and wavelength varies after emission. With a Wien filter measurement and a contrast correlation analysis we demonstrate that the intensity of the source at a certain particle wavelength can be enhanced up to a factor of 6.4 without changing the transverse and longitudinal coherence of the electron beam. In addition, the energy width of the single atom tip emitter was measured to be 377 meV, corresponding to a longitudinal coherence length of 82 nm. The design has potential applications in interferometry, microscopy, and sensor technology.
High-contrast matter-wave interferometry is essential in various fundamental quantum mechanical experiments as well as for technical applications. Thereby, contrast and sensitivity are typically reduced by decoherence and dephasing effects. While decoherence accounts for a general loss of quantum information in a system due to entanglement with the environment, dephasing is due to collective time-dependent external phase shifts, which can be related to temperature drifts, mechanical vibrations, and electromagnetic oscillations. In contrast to decoherence, dephasing can, in principle, be reversed. Here, we demonstrate in experiment and theory a method for the analysis and reduction of the influence of dephasing noise and perturbations consisting of several external frequencies in an electron interferometer. This technique uses the high spatial and temporal resolution of a delay-line detector to reveal and remove dephasing perturbations by second-order correlation analysis. It allows matter-wave experiments under perturbing laboratory conditions and can be applied, in principle, to electron, atom, ion, neutron, and molecule interferometers.
Single-particle interferometers became a remarkable tool in many fields of fundamental research and technical applications, such as sensor technology. Due to their high phase sensitivity, these interferometers are susceptible to dephasing which originates typically from electromagnetic fields, mechanical vibrations or temperature drifts, leading to a reduced contrast in the spatial signal. In opposition to decoherence, where the contrast is reduced due to the entanglement of the quantum state to the environment, dephasing is a collective phase shift of the interference pattern. Therefore, it can in principle be reversed after the measurement if the spatial and temporal information about the particle events in the detection plane is available. Using two-particle correlations, it is possible to reveal the properties of the unperturbed interference pattern, such as contrast and spatial periodicity, and the dephasing characteristics. In this thesis, the second-order correlation analysis of multifrequency dephasing is discussed theoretically and demonstrated experimentally. The second-order correlation theory is derived and the equations are explained in detail. Additionally, the numerical correlation function used to extract the experimental data is provided and it is explained how the discretization influences the accuracy of the obtained parameters. Using an electron biprism interferometer, the validity of our correlation analysis is verified experimentally by applying artificially an external time-varying magnetic field dephasing the temporally integrated interference pattern. It is demonstrated successfully that the parameters of the unperturbed interference pattern can be revealed even if the contrast in the spatial signal is nearly vanished. Furthermore, the characteristics of single- and multifrequency dephasing can be identified and used for the reconstruction of the unperturbed interference pattern. The applicability of our correlation analysis is also investigated by applying external mechanical vibrations in a broad frequency range to the electron biprism interferometer. Here, the amplitude spectrum of the correlation function is used together with a numerical algorithm to identify the unknown dephasing frequencies, amplitudes, and phases. In this way, the vibrational response spectrum of the biprism interferometer including the mechanical resonances could be determined. Our correlation analysis can be applied in principle in all interferometers generating a spatial interference pattern on a detector with high spatial and temporal single-particle resolution. Such detectors are available for electrons, ions, atoms, neutrons, molecules, and photons which enables the application of our method in a wide range of interferometric experiments. In fundamental research, the second-order correlation analysis can be used to distinguish between dephasing and decoherence in experiments where the contrast of the interference pattern has to be determined. This is e.g. relevant for studying the mechanisms of decoherence and testing the limits of quantum mechanical superposition. Our method can also be a useful tool in technical applications to optimize the electromagnetic shielding and vibrational damping of the interferometer by measuring its response spectra. As the correlation analysis is suitable to identify unknown dephasing frequencies and the corresponding amplitudes, it can be applied in sensor technology. At the end of this thesis, a compact sensor for the measurement of time-varying electromagnetic fields based on an electron biprism interferometer is proposed. Due to the wide application possibilities of the described correlation analysis, it is of significant relevance in various fields of single-particle interferometry.
Matter-wave near-field interferometric experiments require interference contrast as high as possible in order to extract information from the interference patterns. One of the tasks to accomplish this requirement is to align the distances between gratings and detection. We present here a method for this precision alignment. An electron beam as a matter-wave source, a diffraction grating, and mask grating were used in this study. The simulations show that the longitudinal scanning of the mask grating with the detection can specify the exact location of the near-field or so-called Talbot distance with the condition of using the gratings with small open fractions. Therefore, the various open fractions were done in the calculation. Due to the lack of commercial gratings with small open fractions, a technique of two overlapping gratings can be applied for changing arbitrary grating shapes and open fractions. We conclude that smaller open fraction of the gratings gives better longitudinal alignment. The results show that the Talbot distance is located at the highest throughput behind the gratings. The present study can provide a method for implementing matter-wave diffraction experiments in the future.