Double-slit Research Articles

Visualizing Double-Slit Interference on a Shoestring

Student misconceptions of the double-slit experiment (Fig. 1) are abundant. The most common ones that we observe include: (1) belief that constructive interference requires both pathlengths to be integer multiples of the wavelength (“L1 = n1λ” and “L2 = n2λ”) rather than only the pathlength difference (ΔL ≡ |L1 – L2| = nλ); (2) failure to understand that the justification for d sin θ = nλ is that d sin θ is a good approximation to ΔL; (3) confusion about the limits in which the approximation d sin θ = nλ is valid; and (4) confusion about the limits in which the approximation sin θ = tan θ = y/D is valid. Most of these misconceptions have been observed in the past. We consider the first of these to be the most damaging, since it will hinder students from understanding interference in other contexts in the future. To address this misconception, we have designed an exercise that strongly reinforces the correct understanding (ΔL = nλ) while also helping overcome the other misconceptions.

Diffraction and interference with run-and-tumble particles

Run-and-tumble particles, frequently considered today for modeling bacterial locomotion, naturally appear outside a biological context as well. Here, we consider them in a quantum mechanical relation, using a wave function to drive their propulsion and tumbling. Such quantum-active motion realizes a jittery motion of Dirac electrons (as in the famous Zitterbewegung): the Dirac electron is a run-and-tumble particle, where the tumbling is between chiralities. We visualize the electron trajectories in single and double slit experiments and discuss their dependence on the spin-direction. In particular, that yields the time-of-arrival statistics of the electrons at the screen. Finally, we observe that away from pure quantum guidance, run-and-tumble particles with suitable spacetime-dependent parameters produce an interference pattern as well.

Time, mourning, and pedagogy in DEVS

ABSTRACT The television series DEVS, written and directed by Alex Garland, and broadcast in 2020, connects to those fears around the advent of technology and certain theories in (or of) physics which undermine concepts of autonomy and free will. Through attention to the cinematic frame, I trace the appeal to a mourned reality in the ‘explanatory’ double-slit experiment lecture scene of the series. I focus on the ways through which a particular interpretation of what is ‘seen’ in the experiment is taught to create a certain narrative of reality which is already displaced. I argue that questions of a mourned reality are rehearsed in theories in (or of) physics in attempts to fix meaning in and as an object. In thinking about the impossibility of seeing another’s sight, I then turn to a reading of Hugh Everett III’s paper which eventually gave rise to the ‘Many Worlds’ interpretation of quantum mechanics. I take up again the question of who and what counts as an observer, and how claims to seeing are undermined through repeated appeals to memory and a placement of the mathematics of the theory outside of time. In a final move, I show that these questions of how to read (an object) return uncannily to the very literary questions of meaning, time and space which Jacques Derrida pursues in ‘FORS’.

How can a random phenomenon between particles be synchronized instantaneously and independently of the distance between said particles?

Entanglement is a random phenomenon that is instantly synchronized, regardless of the space that mediates between entangled particles. However, the instantaneous transmission of information using entanglement is impossible. This is because the instantaneity in the synchronization of non-local outcomes as a consequence of quantum measurement (after the distribution of the entangled pairs) cannot be used for an entanglement-based communication system to transmit information instantaneously. This impossibility stems from the following two reasons: (a) the difficulty of controlling non-local outcomes through local actions without the intervention of an auxiliary channel (classical), and (b) regardless of the previous point, no communication system based on entanglement can be instantaneous due to the distribution of an entangled pair at relativistic speeds, necessary to generate the quantum channel, each time a qubit must be transmitted. Three simple experiments help to clarify this controversial point. In fact, this study establishes what is truly responsible for the impossibility to transmit information instantaneously of any communication system based on entanglement. In this respect, functional models of the internal behavior of quantum measurement, and entanglement were developed, which allow analyzing the instantaneity post-distribution of entangled particles, before and after a quantum measurement, as well as the randomness in the results obtained from a quantum measurement of the entanglement. In this sense, this study establishes a debate about three possible responsible for the aforementioned randomness: the quantum measurement itself, entanglement, and the human intervention. Finally, homology between the entanglement and the double-slit experiment is presented.

Generation of intense phase-stable femtosecond hard X-ray pulse pairs

Coherent nonlinear spectroscopies and imaging in the X-ray domain provide direct insight into the coupled motions of electrons and nuclei with resolution on the electronic length scale and timescale. The experimental realization of such techniques will strongly benefit from access to intense, coherent pairs of femtosecond X-ray pulses. We have observed phase-stable X-ray pulse pairs containing more than 3 × 107 photons at 5.9 keV (2.1 Å) with ∼1 fs duration and 2 to 5 fs separation. The highly directional pulse pairs are manifested by interference fringes in the superfluorescent and seeded stimulated manganese Kα emission induced by an X-ray free-electron laser. The fringes constitute the time-frequency X-ray analog of Young’s double-slit interference, allowing for frequency domain X-ray measurements with attosecond time resolution.

Which-way identification by an asymmetrical double-slit experiment with monochromatic photons

Recently, a laser beam asymmetrical double-slit experiment was proposed and performed, concerning ontological physical reality in quantum mechanics, under an assumption of single-photon interference. In the present study, by controlling better for saturation effects and upgrading the slit’s shape, we succeed in producing new interference samples with acceptable quality. Applying almost the same geometrical set-up, the present experiment makes the ”which-way” identification with higher experimental confidence. In the results, the ontological which-way effect observed in our recent experiment is well reconfirmed without any additional measurement of relative integral intensity.

Spatial coherence of electrically pumped random terahertz lasers

Light sources with high radiance and tailored coherence properties are highly desirable for imaging applications in the mid-infrared and terahertz (THz) spectral regions, which host a large variety of molecular absorptions and distinctive fingerprints to be exploited for sensing and tomography. Here, we characterize the spatial coherence of random multimode THz quantum cascade lasers (QCLs) emitting > mW optical power per mode and showing low divergence (10°–30°), performing a modified Young’s double-slit experiment. Partial spatial coherence values ranging between 0.16 and 0.34 are retrieved, depending on the specific degree of disorder. These values are significantly lower than those (0.82) of conventional Fabry–Perot THz QCLs exploiting an identical active region quantum design. We then incorporate the devised low spatial coherence random lasers into a confocal imaging system with micrometer spatial resolution and demonstrate notable imaging performances, at THz frequencies, against spatial cross talk and speckles.

Nonadiabatic effect on temporal double-slit interference structures in an orthogonal two-color laser field

We theoretically investigate the temporal double-slit interference (DSI) structures in photoelectron momentum distribution driven by an orthogonally polarized two-color (OTC) laser field and focus on the nonadiabatic effect on the subcycle electron dynamics. Distinct discrepancies in the interference structures simulated with a time-dependent Schr\"odinger equation (TDSE) and an adiabatic semiclassical Monte Carlo approach are observed. By adopting the initial conditions derived from the nonadiabatic tunneling picture into the Monte Carlo algorithm, the improved nonadiabatic model well reproduces the TDSE result. Further analysis shows that the improvement is mainly attributed to the nonzero electron initial longitudinal velocity from the nonadiabatic tunneling and moreover, its influence on the subsequent electron dynamics is revealed. Our work demonstrates the sensitivity of the temporal DSI structures in an OTC field to the exit momentum, providing a way for comprehension of the nonadiabatic tunneling electron dynamics.

Time and Space Resolved First Order Optical Interference Between Distinguishable Photon Paths

Interference between different photons occurs and has been observed under diverse experimental conditions. A necessary condition in order to obtain interference fringes is the existence of at least two possible paths and unknown which-path information. If the photon beams have different frequencies, stability of the sources and fast spatially distributed detectors are required in order to detect the time displaced interference fringes. First order optical interference between two truly independent CW laser sources is observed. In contrast with the standard quantum criterion, interference is observed although the photon beams are distinguishable and, from quantum measurements, the path is unequivocally known for each photon beam. Segments of the continuous wave wavetrains are selected with an acousto-optic modulator. Temporal and spatial interference are integrated in a single combined phenomenon via streak camera detection. The displacement of the fringes in the time versus space interferograms evince the trajectories of the labeled photons. These results suggest that in non-degenerate frequency schemes, the ontology has to be refined and the which-path criterion must be precisely formulated. On the one hand, if the query refers to the frequency labeled photons, the path of each red or blue photon is known, whereas on the other hand, if the query is performed in terms of the detected photons, the path is unknown.

Young’s Double Slit Method-Based Higher Order Mode Surface Plasmon Microwave Antenna Sensor: Modeling, Measurements, and Application

This paper proposes Young’s double slit method based high gain broadband higher order mode spoof surface plasmon leaky wave antenna sensor (SSPLWA) for dual beam and sensing applications. Following and mimicking the double slit principle in microwave frequencies, the proposed surface plasmon leaky wave antenna sensor operating on higher order modes has been successfully measured to obtain a wideband of more than 15GHz (88.5%) and generate two simultaneous radiating beams towards the endfire direction with a peak gain of 16.6 dBi. The proposed antenna sensor operates in a broad frequency range from 10GHz-25GHz and maintains a minimum gain of > 10 dBi in the whole operating band. The SSPLWA has been tested by designing two prototypes without and with additional horizontal conducting strips so as to improve the overall gain, reflection and efficiency. The prototype with horizontal strips has been further tested for sensing application i.e. aqueous glucose solutions and it is found that the proposed dual beam sensor is providing high sensitivity and very stable measurement results in terms of resonance frequency shifts or magnitude variations. The proposed antenna sensor has achieved a high peak efficiency of 95 percent and can be very useful for dual beam applications and wireless sensing measurements.

Superluminal, contradiction and unification between quantum theory and special relativity

First, some superluminal phenomena are introduced. Next, based on the complete special relativity which includes the generalized Lorentz transformation (GLT) and superluminal in the spacelike interval, we search contradiction between the uncertainty principle in quantum mechanics and strict classification of the timelike-spacelike intervals in special relativity. Third, we propose new interpretation of the duality in the double-slit experiment that is the particle-wave duality corresponds to the timelike and spacelike intervals, respectively. Such the duality is mutually exclusive and complementary. Fourth, we derive the new LT and GLT for very small space and time, and research possible unification of quantum theory and complete special relativity.

Diffraction and Interference with Run-and-Tumble Particles

Run-and-tumble particles, frequently considered today for modeling bacterial locomotion, naturally appear outside a biological context as well, e.g. for producing waves in the telegraph process. Here, we use a wave function to drive their propulsion and tumbling. Such quantum-active motion realizes a jittery motion of Dirac electrons (as in the famous Zitterbewegung): the Dirac electron is a run-and-tumble particle, where the tumbling is between chiralities. We visualize the trajectories in diffraction and double slit experiments for electrons. In particular, that yields the time-of-arrival statistics of the electrons at the screen. Finally, we observe that away from pure quantum guidance, run-and-tumble particles with suitable spacetime-dependent parameters produce an interference pattern as well.

New explanation of double-slit interference with single quantum based on the theory of spin vector in motion behaving particle-wave duality

New explanation of double-slit interference with single quantum based on the theory of spin vector in motion behaving particle-wave duality

Interference and diffraction experiment using 3D printing and Arduino

Here, we present a 3D printed experimental apparatus that students can use to acquire interference and diffraction quantitative data from light passing through a single or double-slit experiment. We built a linear screw stage with a multiturn potentiometer connected to its leadscrew as a position sensor. Using an Arduino, we collected light intensity data (from a photodiode mounted in the linear stage) as a function of position. The apparatus is a low-cost and compact alternative with data acquisition to optics physics laboratories.

Theory of polarization-averaged core-level molecular-frame photoelectron angular distributions: III. New formula for p- and s-wave interference analogous to Young’s double-slit experiment for core-level photoemission from hetero-diatomic molecules

We present a new variation of Young’s double-slit formula for polarization-averaged molecular-frame photoelectron angular distributions (PA-MFPADs) of hetero-diatomic molecules, which may be used to extract the bond length. So far, empirical analysis of the PA-MFPADs has often been carried out employing Young’s formula in which each of the two atomic centers emits an s-photoelectron wave. The PA-MFPADs, on the other hand, can consist of an interference between the p-wave from the x-ray absorbing atom emitted along the molecular axis and the s-wave scattered by neighboring atom, within the framework of multiple scattering theory. The difference of this p–s wave interference from the commonly used s–s wave interference causes a dramatic change in the interference pattern, especially near the angles perpendicular to the molecular axis. This change involves an additional fringe, urging us to caution when using the conventional Young’s formula for retrieving the bond length. We have derived a new formula analogous to Young’s formula but for the p–s wave interference. The bond lengths retrieved from the PA-MFPADs via the new formula reproduce the original C–O bond lengths used in the reference ab-initio PA-MFPADs within the relative error of 5%. In the high energy regime, this new formula for p–s wave interference converges to the ordinary Young’s formula for the s–s wave interference. We expect it to be used to retrieve the bond length for time-resolved PA-MFPADs instead of the conventional Young’s formula.

Statistical properties of double-slit interference of partially coherent polarization singular vector beams

The Young’s double-slit interference of partially coherent polarization singular vector beams (PC-PSVBs) is investigated both theoretically and experimentally. Unlike the case of scalar or linearly polarized light beams, the far-field interference pattern of PC-PSVB’s have spatial dependence both in horizontal and vertical directions. The visibility of these patterns is governed by the input spatial correlation length. The number of minima along the vertical direction (y-axis) depicts the magnitude of Poincaré-Hopf index (PHI) of the incident beam. Our results reveal that the far-field statistical properties namely, intensity pattern, degree of polarization (DOP) distribution and Stokes-parameters distributions of the PC-PSVBs diffracted through a double-slit are strongly influenced by the spatial correlation length of the incident beam. It is observed that the DOP distribution of the diffracted PC-PSVB does not follow the azimuthally symmetric DOP profile of the input PC-PSVB. Interestingly, the DOP distributions contain the information of the magnitude of PHI of the incident PC-PSVB even for a low value of spatial correlation length. However, the maximum value of DOP deteriorates with the decrease in the input spatial correlation length. Furthermore, the Stokes field (S12(ρ,z)) of the diffracted PC-PSVB contains the information of both the magnitude and polarity of the PHI of the input beam. The experimental results are in good agreement with the theoretical predictions, and may find applications in the areas where the statistical properties of a light field are important.

A double-slit experiment without slits

A double-slit experiment without slits

Coherence Between Different Propagating Surface Plasmon Polariton Modes Excited by Quantum Mechanical Tunnel Junctions

AbstractCoherence between different surface plasmon polariton (SPP) modes excited by inelastically tunneling electrons in biased metal–insulator–metal tunnel junctions (MIM‐TJs) is demonstrated. By employing a dedicated SPP stripe waveguide with MIM‐TJ, an effective double‐slit configuration similar to the Young's experiment is realized for an electrically biased SPP source. The spatial correlation between different SPP modes originates from a single inelastic tunneling event and leads to strong interference in the far‐field, observed as alternate bright and dark fringes in the Fourier plane. The measured fringe‐spacing inversely follows the stripe waveguide length, with upper limit dictated by the SPP propagation length, confirming the SPP mediated spatial correlation. Finite difference time domain simulations support the experimental findings. Also, the experimental and simulation results unambiguously demonstrate the two‐step plasmonic decay process in plasmonic MIM‐TJs. The results presented here provide a simple and robust demonstration of the inherent coherence existing between different decay channels (plasmons and photons) of the inelastically tunneling electrons and can be exploited for plasmonic applications with tailored spatial coherence with implications in plasmon amplification and quantum information processing.

Interference of Two Point Sources Using Smartphones

A simple experimental setup using a smartphone and a pair of speakers is presented to perform an accurate experiment on interference of two point sources. The proposed experiment allows simple but interesting measurements to be done to introduce students to interference and diffraction phenomena. As such, the experiment effectively introduces the classical Young’s double-slit interference experiment, and can be used as a replacement for the classical ripple tank.

Quantum mechanical double slit for molecular scattering.

Interference observed in a double-slit experiment most conclusively demonstrates the wave properties of particles. We construct a quantum mechanical double-slit interferometer by rovibrationally exciting molecular deuterium (D2) in a biaxial (v = 2, j = 2) state using Stark-induced adiabatic Raman passage, where v and j represent the vibrational and rotational quantum numbers, respectively. In D2 (v = 2, j = 2) → D2 (v = 2, j′ = 0) rotational relaxation via a cold collision with ground state helium, the two coherently coupled bond axis orientations in the biaxial state act as two slits that generate two indistinguishable quantum mechanical pathways connecting initial and final states of the colliding system. The interference disappears when we decouple the two orientations of the bond axis by separately constructing the uniaxial states of D2, unequivocally establishing the double-slit action of the biaxial state. This double slit opens new possibilities in the coherent control of molecular collisions.