Two papers in one post this time out. One of these was brought to my attention by Joerg Heber, the other I was reminded of when checking some information for last week’s mathematical post on photons. They fit extremely well together though, and both relate to the photon correlation stuff I was talking about last… Continue reading Bunches and Antibunches of Atoms: Hanbury Brown and Twiss Effects in Ultracold Atoms
Category: Physics
High Excitement in Review: “Quantum information with Rydberg atoms”
I’m a big fan of review articles. For those not in academic science, “review article” means a long (tens of pages) paper collecting together the important results of some field of science, and presenting an overview of the whole thing. These vary somewhat in just how specific they are– some deal with both experiment and… Continue reading High Excitement in Review: “Quantum information with Rydberg atoms”
How Many Physics Professors Does It Take?
Johan Larson emails a suggestion for a post topic: How many profs would it take to offer a good, but not necessarily excellent, undergraduate physics degree? I can give you an empirical answer to this: Six. I say that because in the course of my undergraduate physics degree at Williams, I took classes from only… Continue reading How Many Physics Professors Does It Take?
The Science Mindset List
It’s nearly time for classes to resume, which means it’s time for a zillion stories about Beloit College’s annual Kids These Days List, listing off a bunch of things that this year’s entering college class, who were mostly born in 1992, have always taken for granted. A sample: 1. Few in the class know how… Continue reading The Science Mindset List
Why Antibunching Equals Photons
In my post about how we know photons exist, I make reference to the famous Kimble, Dagenais, and Mandel experiment showing “anti-bunching” of photons emitted from an excited atom. They observed that the probability of recording a second detector “click” a very short time after the first was small. This is conclusive evidence that photons… Continue reading Why Antibunching Equals Photons
Waves: Moving Without Going Anywhere
At the tail end of Tuesday’s post about wind and temperature, I asked a “vaguely related fun bonus question:” If the air molecules that surround us are moving at 500 m/s anyway, why isn’t the speed of sound more like 500 m/s than 300 m/s? This is another one that people are sometimes surprised by.… Continue reading Waves: Moving Without Going Anywhere
Quantum Optics from the Opposite Direction: QED Limits on Laser Intensities
Most of the time, when we talk about seeing quantum effects from light, we talk about extremely weak beams– looking at intensities where one photon more or less represents a significant change in the intensity of the light. Last week, though, Physics Buzz wrote up a paper that goes in the other direction: they suggest… Continue reading Quantum Optics from the Opposite Direction: QED Limits on Laser Intensities
Wind and Temperature: Why Doesn’t Windy Equal Hot?
I got forwarded a physics question last night asking about the connection between wind and temperature, which I’ll paraphrase as: Temperature is related to the motion of the atoms and molecules making a substance up, with faster motion corresponding to higher temperature. So why does it feel warmer when the air is still and why… Continue reading Wind and Temperature: Why Doesn’t Windy Equal Hot?
What Do You Need to Make Cold Atoms? Appendix: “No-Laser” Methods
Last week’s series of posts on the hardware needed for laser cooling and trapping experiments dealt specifically with laser-cooling type experiments. It’s possible, though, to make cold atoms without using laser cooling, using a number of techniques I described in two posts back in January. Those didn’t go into the hardware required, though, so what’s… Continue reading What Do You Need to Make Cold Atoms? Appendix: “No-Laser” Methods
New Physics Blogs
A couple of new-to-me but good physics blogs to point out this week: All That Matters by Joerg Heber. This looks like it will be updated weekly-ish, and has a couple of good entries, including a nice write-up of an ultrafast laser experiment that I had flagged to write about before I got distracted by… Continue reading New Physics Blogs