April 2024 American Journal of PhysicsApril 2024 Issue,

Volume 92, No. 4

Young's double-slit interference demonstration with single photons

The interference of single photons going through a double slit is a compelling demonstration of the wave and particle nature of light in the same experiment. Single photons produced by spontaneous parametric down-conversion can be used for this purpose. However, it is particularly challenging to implement this due to coherency and resolution challenges. In this article, we present a table-top laboratory arrangement suitable for the undergraduate instruction laboratory that overcomes these challenges. The apparatus scans a single detector to produce a plot showing the interference patterns of single photons. We include experimental data obtained using this setup, demonstrating double-slit and single-slit interference as well as quantum erasing through the use of sheet polarizers.


In this issue: April 2024 by Mario Belloni; John Essick; Claire A. Marrache-Kikuchi; Raina Olsen; Beth Parks; B. Cameron Reed; Donald Salisbury; Keith Zengel. DOI: 10.1119/5.0204076


Resource Letter DM1: Dark matter: An overview of theory and experiment by James B. R. Battat. DOI: 10.1119/5.0187346
Editor's Note: One of the most interesting mysteries of physics is that of the invisible matter in the universe. This so-called dark matter makes up a large fraction of the mass of the universe, yet by its very nature, dark matter has remained difficult to detect. This Resource Letter begins by providing readers with a historical overview of the evidence for dark matter and then describes possible dark matter candidates and the techniques being used to try to find them.


Relatvistic acceleration in noninertial frames of a line of objects by Chris Dobson. DOI: 10.1119/5.0144523
Editor's Note: Proper acceleration is applied to an accelerating host spacecraft and an accompanying companion undergoing differing accelerations. The special relativistic analysis determines nine distinct scenarios with resulting differences in proper time elapsed, contraction of the companion craft from the point of view of the host, and somewhat surprising differences in the order of spacetime events from the same perspective. Several aspects could serve in instructors modern physics courses, and the linked videos could assist faculty in educating an even wider audience.

Employing an operator form of the Rodrigues formula to calculate wavefunctions without differential equations by Joseph R. Noonan; Maaz ur Rehman Shah; Luogen Xu; James K. Freericks. DOI: 10.1119/5.0177925
Editor's Note: Quantum-mechanical problems are usually solved by either a direct differential-equations approach or operator methods. In 1940, Schrödinger himself developed an extension of the operator approach known as the factorization method wherein energy eigenstates for all exactly solvable problems can be found without needing to determine the wavefunction. This paper generalizes a strategy for converting the eigenstates to wavefunctions and shows how the method applies to three classic problems: the one-dimensional harmonic oscillator, the three-dimensional isotropic oscillator, and the Coulomb potential. Appropriate for advanced quantum mechanics students.

Experimentation on stochastic trajectories: From Brownian motion to inertial confined dynamics by Azul María Brigante; Corina Révora; Gabriel Fernando Volonnino; Marcos Damián Perez; Gabriela Pasquini; María Gabriela Capeluto. DOI: 10.1119/5.0146444
Editor's Note: This paper shows how colliding beads can be used to demonstrate stochastic trajectories. While the experiment is simple, students can analyze the trajectories using techniques with a range of sophistication, making the experiment appropriate for students at a wide range of levels.

On the Brownian motion of a colloid trapped in optical tweezers: Experiments and simulations by D. Pérez-Guerrero; B. Morales-Cruzado; G. I. Guerrero-García; E. Sarmiento-Gómez. DOI: 10.1119/5.0077571
Editor's Note: Optical tweezers are fascinating tools to manipulate micrometer-size particles, such as cells or colloids, via the confining potential of a laser. This paper shows how this external potential hinders the Brownian motion of a colloid. It presents several usual theoretical approaches, including the Langevin equation, that one could use in class, as well as the Brownian dynamics simulations one can run to predict the trajectories of the confined colloid. It also details some experiments that would allow undergraduate students in a statistical physics course to measure such an effect.

Analytical expressions for the first passage time distribution and hit distribution in two and three dimensions by Alexander Clarkson; Chi-Hang Lam; Hai-Yao Deng. DOI: 10.1119/5.0121165
Editor's Note: The first passage time is a commonly calculated property of diffusive processes that defines, for example, how long it takes for a random walker to travel a given distance from its origin point. Results for one-dimensional systems are commonly presented early in textbooks, especially since they demonstrate useful derivation techniques like the use of inverse Laplace transform. Here, the two- and three-dimensional problem is studied both analytically and numerically, providing a deeper understanding of useful derivation techniques for upper level graduate students.

Young's double-slit interference demonstration with single photons by Bill J. Luo; Leia Francis; Valeria Rodríguez-Fajardo; Enrique J. Galvez; Farbod Khoshnoud. DOI: 10.1119/5.0179131
Editor's Note: This article presents a table-top experiment that acquires the interference pattern from single photons passing through a double-slit. The experiment is carried out using the heralded, single-photon experimental setup now affordable and fairly common in advanced instructional laboratories. By scanning a single-photon detector on a translation stage, this experiment is implemented without the need of an expensive gate-intensified CCD camera. The authors compare the acquired single-slit and double-slit interference patterns to predicted ones and include a quantum eraser measurement. The experiments are dramatic demonstrations of wave-particle quantum effects and are excellent additions to the collection of single-photon experiments that have been developed over the past several years for the advanced instructional laboratory curriculum.


Using a Minecraft virtual workspace for learning digital electronics by Carl Faust. DOI: 10.1119/5.0170091
Editor's Note: Looking for new ways to connect with your students or to get your students to connect with each other? If so, Minecraft may be for you! In this paper you'll learn how to use the best-selling video game in history to develop digital electronics activities that teach concepts as simple as basic logic gates or as complicated as the emulation of a whole working computer.

Erratum: “Comment on projectile motion with quadratic drag using an inverse velocity expansion” [Am. J. Phys. 90, 861 (2022)] by Antonio Corvo. DOI: 10.1119/5.0188956


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