As part of developing a Bell’s Inequality Test of Quantum Mechanics laboratory at CWU we have investigated classical interference using a Fabry-Perot and a Mach-Zehnder interferometer. The classical interference investigation was done using several HeNe lasers of different wavelengths. Optimization of data collection for the classical systems was accomplished by fabricating several pieces: a motorized micrometer platform, building a mount for a piezo electric tube, and building a fringe counting circuit. To investigate quantum interference the same Mach-Zhender interferometer was used but the HeNe laser beam was attenuated. We investigated alternative methods for attenuating the HeNe laser beam. An SBIG ST-7 CCD camera was evaluated for use as a single photon detector and used to collect data from the Mach-Zehnder interferometer. The results were compared with results using a single photon counting module. The results were consistent with the predictions of single photon interference in the Mach-Zehnder interferometer.
As part of developing a Bell’s Inequality Test of Quantum Mechanics laboratory at CWU we have investigated classical interference using a Fabry-Perot and a Mach-Zehnder interferometer. The classical interference investigation was done using several HeNe lasers of different wavelengths. Optimization of data collection for the classical systems was accomplished by fabricating several pieces: a motorized micrometer platform, building a mount for a piezo electric tube, and building a fringe counting circuit. To investigate quantum interference the same Mach-Zhender interferometer was used but the HeNe laser beam was attenuated. We investigated alternative methods for attenuating the HeNe laser beam. An SBIG ST-7 CCD camera was evaluated for use as a single photon detector and used to collect data from the Mach-Zehnder interferometer. The results were compared with results using a single photon counting module. The results were consistent with the predictions of single photon interference in the Mach-Zehnder interferometer.
This project represents the initial phase of developing a Bell’s Inequality Test of Quantum Mechanics laboratory at Central Washington University. We set up and performed an investigation of the interference of light using a double slit apparatus. For the experiment, a 632.8 HeNe laser beam was passed through an optical system consisting of mirrors, neutral density filters, linear polarizers, irises, multiple lenses and a pinhole. The light was spatially filtered, producing a clean profile, and collimated by the placement of the irises, lenses, and pinhole within the path of the light. The beam intensity was varied using the neutral density filters and polarizers to obtain interference patterns consistent with single photon events. A SBIG ST-7 CCD camera was used as detector and the interference fringes measured using pixel specifications of the CCD chip. The camera was evaluated for effectiveness as a single photon detector by attenuating the beam until its irradiance was consistent with single photon events in the camera pixels for one exposure and examining the signal. These attenuation procedures were then employed using single photon counting modules to detect the interference pattern. The single photon counting modules provided a TTL signal corresponding with single photon detection. A statistical analysis of two detector’s counts is consistent with detection of the phenomenon of single photon interference.
In this two-part experiment, we studied the interference pattern of a laser pointer interfering with itself through a Mach-Zehnder interferometer as well as tested Bell’s Inequality for entangled particles via parametric down conversion. The predicted results were a fringe pattern that was purely circular with distinct fringes, however, the results of the laser pointer interference were inconclusive due to significant error in the alignment of the interferometer. In reference to the second part of our lab, due to COVID-19 restrictions, time ran out for us to complete data collection of the coincidence counts between the down converted beams of our Gallium Nitride laser. We attributed the lack of coincidence counts to error in the precision of the alignment of the optical apparatus. Thus, we used reference data instead to calculate the statistic, S=2.31 ± 0.04, to compare with Bell’s Inequality of |S| ≤ 2. Our result using the reference data did exceed Bell’s Inequality, as was expected of quantum mechanics, being non-local.
Abstract The superposition states, allowed by quantum theory, are dramatically diverse with respect to classical states and represent the true quantum states. By using a Mach-Zehnder interferometer we experimentally show how a single photon in a polarization superposition state can produce interference. The experimental setup includes a strongly attenuated laser source, polarizing beam splitters, half-waveplates, polarizers and single-photon detectors. The experimental activity has been performed with high-school students and teachers in several different contexts.
Quantum superposition is the heart of quantum mechanics as mentioned by Dirac and Feynman. In an interferometric system, single photon self-interference has been intensively studied over the last several decades in both quantum and classical regimes. In Born rule tests, the Sorkin parameter indicates the maximum number of possible quantum superposition allowed to the input photons entering an interferometer, where multi-photon interference fringe is equivalent to that of a classical version by a laser. Here, an attenuated laser light in a quantum regime is investigated for self-interference in a Mach-Zehnder interferometer, and the results are compared with its classical version. The equivalent result supports the Born rule tests, where the classical interference originates in the superposition of individual single-photon self-interferences. This understanding sheds light on the fundamental physics of quantum features between bipartite systems.
Quantum superposition is the heart of quantum mechanics as mentioned by Dirac and Feynman. In an interferometric system, single photon self-interference has been intensively studied over the last several decades in both quantum and classical regimes. In Born rule tests, the Sorkin parameter indicates the maximum number of possible quantum superposition allowed to the input photons entering an interferometer, where multi-photon interference fringe is equivalent to that of a classical version by a laser. Here, an attenuated laser light in a quantum regime is investigated for self-interference in a Mach-Zehnder interferometer, and the results are compared with its classical version. The resulting equivalent results support the Born rule tests, where the classical interference originates in the superposition of individual single-photon self-interferences. This understanding sheds light on the fundamental physics of quantum features between bipartite systems.
A new fourth-order interference experiment based on detecting photon pairs in coincidence has been carried out. A Mach-Zehnder type of interferometer is used, with the two photons generated simultaneously in the process of down-conversion as inputs and two photon counting detectors at the two outputs. The optical path difference can be varied piezoelectrically. It is found that the coincidence counting rate, after subtraction of accidentals, exhibits a sinusoidal variation with the optical path difference as predicted by quantum mechanics, but in violation of the laws of classical optics. This is another non-classical interference effeet. By contrast, two light beams derived from a He:Ne laser used as inputs to the interferometer, do not produce any fourth order interference.