I generally think of the Economist as having excellent science reporting, but I have to admit that I only read it sporadically these days, so maybe my information is out of date. This article on some recent experiments in the foundations of quantum mechanics is way, way below the standard I’d expect from them.
The article claims that
Now two groups of physicists, working independently, have demonstrated that nature is indeed real when unobserved.
Your skepticism level should spike whenever you read an article claiming that experimental results have confirmed some deep-sounding-yet-vague philosophical idea.
When the article gets down to details, it says a bunch of things that are just wrong:
In the 1990s a physicist called Lucien Hardy proposed a thought experiment that makes nonsense of the famous interaction between matter and antimatter€”that when a particle meets its antiparticle, the pair always annihilate one another in a burst of energy. Dr Hardy's scheme left open the possibility that in some cases when their interaction is not observed a particle and an antiparticle could interact with one another and survive.
This makes no sense. It’s quite common for a particle and its antiparticle to interact without annihilating each other. There’s nothing paradoxical about that.
Later on, we have
The stunning result, though, was that in some places the number of photons was actually less than zero. Fewer than zero particles being present usually means that you have antiparticles instead. But there is no such thing as an antiphoton (photons are their own antiparticles, and are pure energy in any case), so that cannot apply here.
Where to begin? First, I don’t believe the statement that the researchers measured “less than zero” (or even “fewer than zero”) photons. Did they have a photomultiplier tube that clicked -17 times? The actual articles by the two experimental groups contain no claims of anything that could be described in this way.
Second, the idea that fewer than zero particles means antiparticles isn’t really true. There was a theory due to Dirac a long time ago in which positrons (the antiparticles of electrons) were regarded as “holes” that were sort of like negative numbers of electrons, but that theory doesn’t really fit into modern particle physics in any nice way as far as I know.
Finally, can we please ban the phrase “photons are pure energy”? There’s no meaningful sense in which that’s true.
Now I know that science journalists have a tough job, particularly when reporting on very abstract things such as quantum physics. I have no objection at all to their simplifying things to make them clearer. But the above statements aren’t simplifications; they’re just wrong.
These experimental results seem to be a confirmation of a “paradox” in which joint probabilities of two quantities don’t obey the rules that you’d expect classically. Like other similar paradoxes, it’s a nice example of the ways in which quantum mechanics is “spooky,” but I don’t see how the results say anything new about whether reality exists when you’re not looking (whatever that even means).
There’s a common problem in journalism about the foundations of quantum mechanics. As my friend John Baez said a long time ago,
Newspapers tend to report the results of these fundamentals-of-QM experiments as if they were shocking and inexplicable threats to known physics. It’s gotten to the point where whenever I read the introduction to one of these articles, I close my eyes and predict what the reported results will be, and I’m always right. The results are always consistent with simply taking quantum mechanics at face value.
The Economist article goes pretty far (if not all the way) down this route. It takes a clever and interesting experimental result and blows it up into something much spookier than it is. The result does follow precisely the pattern Baez describes: it’s exactly what standard quantum mechanics predicted all along.
Please note that I’m not criticizing the experimenters here: as far as I can tell, they’ve done a difficult and very interesting experiment and described their results accurately. I don’t see anything in their papers that would justify the silly interpretation placed on it by the Economist.
By the way, I got the Baez quote above from a web page by Matt McIrvin which quotes Baez. I can’t find this quote on Baez’s own web site, not that I looked all that hard. Matt has great things to say about the interpretation of quantum mechanics, by the way. If you’re at all interested in this subject, please read this page in addion to — or better yet instead of — the many silly things that have been written on the subject. John Baez has said a bunch of really smart things on the subject in various newsgroup posts over the years as well. He collected some of them here, but as far as I know he hasn’t written up anything more polished.
