{"id":2585,"date":"2008-05-09T09:35:08","date_gmt":"2008-05-09T09:35:08","guid":{"rendered":"http:\/\/scienceblogs.com\/principles\/2008\/05\/09\/whats-wrong-with-atom-laser\/"},"modified":"2008-05-09T09:35:08","modified_gmt":"2008-05-09T09:35:08","slug":"whats-wrong-with-atom-laser","status":"publish","type":"post","link":"http:\/\/chadorzel.com\/principles\/2008\/05\/09\/whats-wrong-with-atom-laser\/","title":{"rendered":"What’s Wrong with “Atom Laser”"},"content":{"rendered":"

There’s a news piece in Physics World<\/cite> this week titled “Atom laser makes its first measurement<\/a>” and you might think this would be right up my alley. Mostly, though, it serves to remind me that the term “atom laser” has always kind of pissed me off.<\/p>\n

This is somewhat ironic, as it’s a beautiful piece of “framing,” the sort of thing I’ve spoken in favor of numerous times here. I have a principled technical objection to the term, though, in that I think the analogy it draws is deliberately misleading.<\/p>\n

I should stress that there’s really nothing wrong with the analogy on the face of it. The basic idea is that there is a parallel to be drawn between a Bose-Einstein condensate (BEC) and a laser– a BEC is a macroscopic number of atoms occupying a single quantum state (at least, that’s the high school physics explanation), while a laser can be thought of as a macroscopic number of photons occupying a single quantum state (in this case, a single mode of the electromagnetic field, with a particular frequency, direction, and polarization). The process by which atoms in a vapor form a BEC is directly analogous to the stimulated emission process by which the photons end up in a single laser mode, and you can draw valid analogies between various laser components and the elements of a BEC experiment (with the important caveat that all “atom lasers” to date have been Q-switched lasers).<\/p>\n

The problem has to do with the way this analogy is deployed, and the meaning of the word “macroscopic.”<\/p>\n

<\/p>\n

“Macroscopic” in the context of atoms in a BEC means “a few million atoms.” “Macroscopic” in the context of laser physics is vastly bigger– a cheap laser pointer will put out something like 1015<\/sup> photons per second<\/strong>. That’s nine orders of magnitude difference, assuming you can make a BEC every few seconds.<\/p>\n

This is the source of the problem with “atom laser,” for me. The analogy is most often used in press materials and the like, where it’s intended to evoke the vast range of technologies that depend on optical lasers. This makes people sit up and say “Wow! Lasers are good for lots of things, so atom lasers must be great stuff.”<\/p>\n

The problem is, most of the technologies that make ordinary lasers useful rely on the laser as nothing more than a really bright source of light. The laser UPC scanner in the grocery store doesn’t depend on the coherence properties of the light in any significant way– you could do the same thing with lamps, lenses, and color filters. It’s just using the laser as a convenient way to get a bright, narrow beam of light.<\/p>\n

This is exactly the point where the “atom laser” analogy is weakest, though. An optical laser that only produced a million photons per second would be pretty much useless as a technology. The number of atoms in a typical BEC just isn’t large enough to be the basis for lithography techniques, or anything like that. You can get vastly higher throughput from a collimated atomic beam apparatus (the equivalent of using lamps, lenses, and filters for light) than you can from a BEC, and that’s still not nearly enough for, say, lithographic chip manufacture.<\/p>\n

So, as a way of publicizing BEC research, the term “atom laser” has always seemed a little more deceptive to me than the usual lies-to-children explanations we use in press releases and the like. There’s no denying that it’s effective, but the analogy breaks down exactly at the point where you would want it to be strongest.<\/p>\n

Ironically, this is exactly the sort of narrow, technical objection that leads lots of people to recoil from the notion of “framing” scientific results (those who are arguing in good faith, anyway). I tend to think that this is a more pernicious error than the usual “framing”-induced mistakes, but then, I’m sure most of the people complaining about “framing” feel the same way about whatever they’re complaining about.<\/p>\n

Then again, most of the actual experiments that have been done with BEC’s don’t use the coherence properties of the condensate any more than a supermarket scanner uses the coherence properties of optical lasers– they’re just using it as a convenient source of really cold atoms. So, maybe it’s not as bad an analogy as I’ve been thinking…<\/p>\n","protected":false},"excerpt":{"rendered":"

There’s a news piece in Physics World this week titled “Atom laser makes its first measurement” and you might think this would be right up my alley. Mostly, though, it serves to remind me that the term “atom laser” has always kind of pissed me off. This is somewhat ironic, as it’s a beautiful piece… Continue reading What’s Wrong with “Atom Laser”<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"1","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[19],"tags":[],"class_list":["post-2585","post","type-post","status-publish","format-standard","hentry","category-experiment","entry"],"_links":{"self":[{"href":"http:\/\/chadorzel.com\/principles\/wp-json\/wp\/v2\/posts\/2585","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/chadorzel.com\/principles\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/chadorzel.com\/principles\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/chadorzel.com\/principles\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"http:\/\/chadorzel.com\/principles\/wp-json\/wp\/v2\/comments?post=2585"}],"version-history":[{"count":0,"href":"http:\/\/chadorzel.com\/principles\/wp-json\/wp\/v2\/posts\/2585\/revisions"}],"wp:attachment":[{"href":"http:\/\/chadorzel.com\/principles\/wp-json\/wp\/v2\/media?parent=2585"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/chadorzel.com\/principles\/wp-json\/wp\/v2\/categories?post=2585"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/chadorzel.com\/principles\/wp-json\/wp\/v2\/tags?post=2585"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}