At ACSME2019, we presented early work on Virtual Reality (VR) software for correcting student misconceptions related to Newton’s laws. This software now runs on the next generation headsets, which has enabled us to scale the experience to entire classes. Since 2019, we have collected data from 109 students who have used VR as part of their physics coursework at ANU. Inspired by questions from Force Concept Inventory (FCI; Hestenes, Wells, & Swackhamer, 1992), our VR experience asks students to play with a basketball and decide which forces act on the ball. They are presented with the world that represents their choices, and therefore manifests their misconceptions. A narrator guides them with feedback to reconsider and reflect on their choices until they choose the correct answer. When compared with 350 students who did not use VR but have undertaken the same course at ANU over several years, there is a statistically significant improvement in FCI metrics. Both overall score and questions relating to relevant misconceptions show improvements. The non-VR and VR groups both have equivalent baselines in their pre-course FCI test. We also present recent work on a multiplayer, electromagnetism sandbox to allow for VR-based tutorials targeting EM visualisation and concepts. REFERENCE Hestenes, D., Wells, M., & Swackhamer, G., (1992) Force Concept Inventory, The Physics Teacher, 30, 141-151.

This activity is the basis of a ‘lab’ session run with first year students at ANU, who are learning about the Lorentz Force and electromagnetism more generally. Using just 4 simple objects, the goal is to build the world’s simplest electric train, and then explain its operation using a physics model. The fantastic aspect of this system is that it can be understood using everything from very simple conceptual models introduced in high school as early as year 9-10, through to a full analysis using Maxwell’s Equations (2nd/3rd year university). The opportunity to use this system as a way to revisit concepts and build a progressively deeper understanding of electromagnetism over several years is profound. It also incorporates an understanding of mechanics, friction, and is quite frankly, very cool and a lot of fun. The session will first give everyone the chance to undertake the challenge themselves (no Google!). Afterwards we’ll explain its operation using several models and share how the theoretical description can be anything from conceptual, to back of envelope, and finally a full analytic calculation.

Virtual reality (VR) has reached a point of development where its accessibility and immersion is sufficient to give realistic and memorable experiences. One of the most exciting possibilities is the ability to visualise invisible or impossible worlds. For example, electricity and magnetism are frequently challenging concepts to teach, in particular because students need to build a mental model of what a ‘field’ is. VR gives us the ability to give people a realistic representation of vector fields, of far higher complexity than that possible on a traditional computer screen. Furthermore, it can allow dynamic manipulation, simulation, and testing – effectively offering students a sandbox in which to experiment with these systems. Another exciting application is the use of VR to allow students to experience worlds that manifest their misconceptions. Led by misconceptions well studied and measured using the Force Concept Inventory (Hestenes, Wells, & Swackhamer, 1992), students can be asked to predict what forces exist in a given situation. They are then given a world in which those forces are present, and thus if incorrect, experience a situation that behaves counter-intuitively, thereby triggering cognitive dissonance. They can then be guided via narration, or an instructor to reassess their views and ideally correct their misconception. At ANU, we have been developing both of these apps over the last two years. We will share some positive preliminary results with small groups of student, both qualitative and quantitative.

This corrects the article DOI: 10.1103/PhysRevLett.113.013002.

A Bose-Einstein condensate is used as an atomic source for a high precision sensor. A 5×10^{6}  atom F=1 spinor condensate of ^{87}Rb is released into free fall for up to 750 ms and probed with a T=130  ms Mach-Zehnder atom interferometer based on Bragg transitions. The Bragg interferometer simultaneously addresses the three magnetic states |m_{f}=1,0,-1⟩, facilitating a simultaneous measurement of the acceleration due to gravity with a 1000 run precision of Δg/g=1.45×10^{-9} and the magnetic field gradient to a precision of 120  pT/m.

Large momentum transfer( LM T) beamsplitting in atom interferometry is review ed,focusing on the use of Bloch Oscillations to achieve high momentum separation w ithout loss of visibility. Phase sensitivity w ith a fringe visibility of 7% is observed in a horizontally guided,acceleration-sensitive atom interferometer w ith a momentum separation of 80k betw een its arms.In addition,a 510 k beamsplitter is demonstrated.更多还原

In weakly nonlinear dispersive systems, solitons are spatially localized solutions which propagate without changing shape through a delicate balance between dispersion and self-focusing nonlinear effects. These states have been extensively studied in Bose-Einstein condensates, where interatomic interactions give rise to such nonlinearities. Previous experimental work with matter wave solitons has been limited to static intensity profiles. The creation of matter wave breathers--dispersionless soliton-like states with collective oscillation frequencies driven by attractive mean-field interactions--have been of theoretical interest due to the exotic behaviour of interacting matter wave systems. Here, using an attractively interacting Bose-Einstein condensate, we present the first observation of matter wave breathers. A comparison between experimental data and a cubic-quintic Gross-Pitaevskii equation suggests that previously unobserved three-body interactions may play an important role in this system. The observation of long lived stable breathers in an attractively interacting matter wave system indicates that there is a wide range of previously unobserved, but theoretically predicted, effects that are now experimentally accessible.

Since their development in the late 1980s, cheap, reliable external cavity diode lasers (ECDLs) have replaced complex and expensive traditional dye and Titanium Sapphire lasers as the workhorse laser of atomic physics labs(1,2). Their versatility and prolific use throughout atomic physics in applications such as absorption spectroscopy and laser cooling(1,2) makes it imperative for incoming students to gain a firm practical understanding of these lasers. This publication builds upon the seminal work by Wieman(3), updating components, and providing a video tutorial. The setup, frequency locking and performance characterization of an ECDL will be described. Discussion of component selection and proper mounting of both diodes and gratings, the factors affecting mode selection within the cavity, proper alignment for optimal external feedback, optics setup for coarse and fine frequency sensitive measurements, a brief overview of laser locking techniques, and laser linewidth measurements are included.

Atom interferometers have been used to measure acceleration with at best a T2 scaling in sensitivity as the interferometer time T is increased. This limits the sensitivity to acceleration which is theoretically achievable by these configurations for a given frequency of acceleration. We predict and experimentally measure the acceleration-sensitive phase shift of a large-momentum-transfer atom interferometer based upon Bloch oscillations. Using this novel interferometric scheme we demonstrate an improved scaling of sensitivity which will scale as T3. This enhanced scaling will allow an increase in achievable sensitivity for any given frequency of an oscillatory acceleration signal, which will be of particular use for inertial and navigational sensors, and proposed gravitational wave detectors. A straightforward extension should allow a T4 scaling in acceleration sensitivity.

The role of source cloud spatial coherence in a Mach-Zehnder-type atom interferometer is experimentally investigated. The visibility and contrast of a Bose-Einstein condensate (BEC) and three thermal sources with varying spatial coherence are compared as a function of interferometer time. At short times, the fringe visibility of a BEC source approaches 100% nearly independent of pi pulse efficiency, while thermal sources have fringe visibilities limited to the pi pulse efficiency. More importantly for precision measurement systems, the BEC source maintains interference at interferometer times significantly beyond the thermal source.

Two simple external cavity diode laser designs using fibre pigtailed gain chips are tested and their properties compared with a high end DBR fibre laser. These ECDLs demonstrate a FWHM linewidth as low as 5.2kHz with a fitted Lorentzian FWHM linewidth as low as 1.6kHz. Tuning ranges of 200nm covering 1420nm to 1620nm were demonstrated. To the best of our knowledge these are the narrowest linewidth and most broadly tunable external cavity diode lasers reported to date. The improvement in linewidth is attributed to greatly enhanced acoustic isolation allowed by using fiber coupled gain chips and by replacing kinematic mounts with a pair of rotatable wedges for cavity alignment which eliminates acoustic resonances. A detailed description and discussion of techniques used to characterize the frequency noise and linewidths of these lasers is provided.

This paper presents the first realisation of a simultaneous $^{87}$Rb -$^{85}$Rb Mach-Zehnder atom interferometer with Bose-condensed atoms. A number of ambitious proposals for precise terrestrial and space based tests of the Weak Equivalence Principle rely on such a system. This implementation utilises hybrid magnetic-optical trapping to produce spatially overlapped condensates with a duty cycle of 20s. A horizontal optical waveguide with co-linear Bragg beamsplitters and mirrors is used to simultaneously address both isotopes in the interferometer. We observe a non-linear phase shift on a non-interacting $^{85}$Rb interferometer as a function of interferometer time, $T$, which we show arises from inter-isotope scattering with the co-incident $^{87}$Rb interferometer. A discussion of implications for future experiments is given.

We present the first realization of a solitonic atom interferometer. A Bose-Einstein condensate of 1×10(4) atoms of rubidium-85 is loaded into a horizontal optical waveguide. Through the use of a Feshbach resonance, the s-wave scattering length of the 85Rb atoms is tuned to a small negative value. This attractive atomic interaction then balances the inherent matter-wave dispersion, creating a bright solitonic matter wave. A Mach-Zehnder interferometer is constructed by driving Bragg transitions with the use of an optical lattice colinear with the waveguide. Matter-wave propagation and interferometric fringe visibility are compared across a range of s-wave scattering values including repulsive, attractive and noninteracting values. The solitonic matter wave is found to significantly increase fringe visibility even compared with a noninteracting cloud.

An atom interferometer and an optical frequency comb measure the Compton frequency of a cesium atom, creating a "clock" that weighs atoms. [Also see Report by Lan et al. ]

We present a precision gravimeter based on coherent Bragg diffraction of freely falling cold atoms. Traditionally, atomic gravimeters have used stimulated Raman transitions to separate clouds in momentum space by driving transitions between two internal atomic states. Bragg interferometers utilize only a single internal state, and can therefore be less susceptible to environmental perturbations. Here we show that atoms extracted from a magneto-optical trap using an accelerating optical lattice are a suitable source for a Bragg atom interferometer, allowing efficient beamsplitting and subsequent separation of momentum states for detection. Despite the inherently multi-state nature of atom diffraction, we are able to build a Mach-Zehnder interferometer using Bragg scattering which achieves a sensitivity to the gravitational acceleration of Delta g/g = 2.7 x 10(-9) with an integration time of 1000s. The device can also be converted to a gravity gradiometer by a simple modification of the light pulse sequence.

We demonstrate phase sensitivity in a horizontally guided, acceleration-sensitive atom interferometer with a momentum separation of $80\ensuremath{\hbar}k$ between its arms. A fringe visibility of 7% is observed. Our coherent pulse sequence accelerates the cold cloud in an optical waveguide, an inherently scalable route to large momentum separation and high sensitivity. We maintain coherence at high momentum separation due to both the transverse confinement provided by the guide and our use of optical $\ensuremath{\delta}$-kick cooling on our cold-atom cloud. We also construct a horizontal interferometric gradiometer to measure the longitudinal curvature of our optical waveguide.

We demonstrate a horizontal, linearly guided Mach Zehnder atom interferometer in an optical waveguide. Intended as a proof-of-principle experiment, the interferometer utilises a Bose-Einstein condensate in the magnetically insensitive |F=1,mF=0> state of Rubidium-87 as an acceleration sensitive test mass. We achieve a modest sensitivity to acceleration of da = 7x10^-4 m/s^2. Our fringe visibility is as high as 38% in this optically guided atom interferometer. We observe a time-of-flight in the waveguide of over half a second, demonstrating the utility of our optical guide for future sensors.

Over 250 years ago Sir Isaac Newton, inspired by an apple falling from a tree in his orchard (Stuckeley 1752), made the mental leap to conjecture that the same force that caused this apple to fall also held the Moon to the Earth. This stimulated him to develop his Law of Gravitation, and led to the principle that all objects fall with the same acceleration irrespective of their mass, as observed by Galileo Galilei. Over 250 years ago, these scientists understood gravity as well as many people do today. In reality, we still measure gravity by dropping a proverbial apple – a falling test mass whose trajectory we measure through space–time. However, developments over the past two centuries have led to a vast improvement in our measurement precision. With the advent of the optical laser and atom interferometers over the past 50 years, we have far superior rulers, and far superior clocks with which to make such a measurement.

We present a narrow linewidth continuous laser source with over 11 W output power at 780 nm, based on single-pass frequency doubling of an amplified 1560 nm fibre laser with 36% efficiency. This source offers a combination of high power, simplicity, mode quality and stability. Without any active stabilization, the linewidth is measured to be below 10 kHz. The fibre seed is tunable over 60 GHz, which allows access to the D₂ transitions in ⁸⁷Rb and ⁸⁵Rb, providing a viable high-power source for laser cooling as well as for large-momentum-transfer beamsplitters in atom interferometry. Sources of this type will pave the way for a new generation of high flux, high duty-cycle degenerate quantum gas experiments.