Wednesday, April 11, 2007

A paper and a wager

One paper on the arxiv that I need to read more closely: cond-mat/0701728, Sukhorukov et al., Conditional statistics of electron transport in interacting nanoscale conductors. This paper, a collaboration between Rochester, Geneva, and ETH Zurich, looks at the noise properties of transport through a quantum dot in the presence of a charge detector, in this case a quantum point contact (QPC). A QPC is a constriction in a 2d electron gas with a width modulated by gates. If the QPC is tweaked such that it's right on the boundary of pinching off a transverse electronic mode, its conductance can depend strongly on the local charge environment, which acts like an extra gate. By monitoring the conductance of the QPC, the authors can watch tunneling events in the capacitively coupled quantum dot. The presence of an electron on the dot reduces the conductance of the QPC. Like most of the very pretty work to come out of Enslinn's group at ETH, the quantum dot and QPC are defined through local AFM-based surface oxidation of a shallow 2d electron gas in a GaAs/AlGaAs heterostructure. What I don't understand about this paper is a statement in the introduction: "An important property of the QPC charge detector is its noninvasiveness: the system physically affects the detector, not visa-versa." Strictly speaking, this just can't be right. If the quantum dot is capacitively coupled to the QPC sufficiently to modulate the QPC current flow, there has to be back-action of the QPC on the dot charge. While that interaction may be small, it can't be nonexistent, as far as I can see.

An unrelated anecdote: some of you may remember this post, where I talked about Steorn, an Irish company that took out a full-page ad in the Economist magazine looking for scientists to act as a "jury" of some sort and evaluate their "free energy" machine. Well, it would appear that Steorn did manage to find some scientists willing to act as a "jury", whatever that means, and will release some sort of report of their findings this Friday. I actually did communicate with Steorn last fall; while they had some interest in talking to me, they did not come close to answering my questions about how their jury process was supposed to work (e.g., would scientists actually be able to play with the gadget in an off-site laboratory; did Steorn really mean that their machine produced energy, or were they trying to finesse conventional jargon by talking about "coefficients of performance greater than one" (which may mean nothing for a refrigerator, for example)). I'm willing to wager that they have not discovered a loophole in the first law of thermodynamics. It will be interesting to hear what they report, and whether any actual scientists would be willing to stand up and back Steorn's claims.

Update: Sean McCarthy of Steorn informs me that my comments above are inaccurate, and that, indeed, their evaluation will be based on tests specified by their "jury" in an independent laboratory. My apologies for any confusion. This was not clear to me last fall, and I haven't been following this in the interim. I should also point out that my interactions with them were entirely cordial and businesslike.

I reiterate, though, that I think there is zero chance that these folks have been able to circumvent conservation of energy. If they have, I will happily eat my words, as this would be the biggest science story of the century. Extraordinary claims require extraordinary evidence.

23 comments:

Aaron said...

I just can't help myself so, in the immortal words of this country's greatest mind, "Young lady, in this house we obey the laws of thermodynamics!" Leave it to the Simpson's to have a quote appropriate for any occasion.

By the way, I actually was almost on this "jury" but had to decline when the oompah-loompah's started singing while I was reviewing Steorn's data.

Anonymous said...

..."and will release some sort of report of their findings this Friday"

This is not true. The update on Friday will be a video interview with Sean (Steorn's CEO) that will have some kind of jury update. I'm sure jury findings will not be part of the information. They will also be posting some kind of technical specs on their site on Friday as well. Not expecting much, maybe some example output figures, etc...

Anonymous said...

This just sounds like sour grapes for not being good enough to be selected for the jury.

You scientists need to open your mind to new ideas a little more.

Anonymous said...

If one is interested and has time, there is a thread of quotes from Steorn's various discussions with forum members. It should give you a pretty good idea of what they are about...or at least what Sean says they are about.

Anonymous said...

Seems that Sean (CEO of Steorn) is going to check his correspondence regarding discussions with Doug. He will post tomorrow on the their forum.

Doug Natelson said...

They asked me; I declined. There isn't much correspondence - two emails from me, IIRC. Discussion was done over the phone. Believe me, I would love it if I were wrong - it'd be the biggest scientific news of the century. However, having an open mind doesn't mean believing everything people tell you uncritically.

Doug Natelson said...

I will append my two emails about this in the morning.

Anonymous said...

For clarity - are you saying you were invited? But declined? And you declining for the reason that they didn't or wouldn't answer the questions of which you gave some examples?

Anonymous said...

To aaron - are you pulling out log? Or can you produce some proof of your claim that you were almost on the jury? And how did you even get data to review before being on the jury?

Doug Natelson said...

Anonymous - Aaron is kidding around. Yes, they contacted me to invite me, both by email and by telephone. The main reason I declined had nothing to do with them - between when I'd emailed them (the day after their big ad in the Economist last August) and when the contacted me, I was appointed to head a faculty search committee that was going to be interviewing job candidates throughout January. There was no way I could make it to Ireland without neglecting my job, so I said "no thanks." At the same time, I did ask several questions of the kind I mentioned, more than once, and they didn't answer them. To give them the benefit of the doubt, it's possible that they just didn't want to talk about anything at all technical until I'd signed an NDA or something.

However, I still think that their plan is a bit odd. They talk about having their jury review their data, not actually do any testing themselves. That would never satisfy me - my grad students can attest that I like to actually see the data being taken. You only really know what's going on if you do the test yourself, soup to nuts.
That's not being close-minded, it's being careful.

Anonymous said...

"...They talk about having their jury review their data, not actually do any testing themselves. That would never satisfy me - my grad students can attest that I like to actually see the data being taken. You only really know what's going on if you do the test yourself, soup to nuts.
That's not being close-minded, it's being careful."

I'm not sure where you got that idea. From what I understand the jury are given everything they need to completely reproduce the effect, on their own time and in their own environment. I mean, come on, the whole point of the jury is to prove to the scientific world that what they have is true. I'm not saying that is what the jury will find, but that is certainly the whole point of the excercise.

Doug Natelson said...

Well, the original challenge page, to which I'd linked in my post last August (though the link is now dead), had said that the jury was to examine Steorn's data and tests - not that they would be able to make tests themselves. I asked this explicitly and did not get an answer.

If I'm wrong, then great - the less restrictions on the process the better.

Anonymous said...

Hi doug,

while i fully believe this a scam i'm impressed that someone with your pedigree still took the time to consider looking into this...

Doug Natelson said...

Thanks for the kind words. Mostly I'm a sucker for provocation, as my regular readers can attest (kidding!). I hope someone with credibility is involved - endorsement by unqualified people would only muddy the waters.

If it's a scam, I don't see the motivation, unless it's a crude way to drum up publicity and venture capital. Self-deception seems more likely to me. Heck, if they really have discovered a free energy machine, drinks are on me.

Anonymous said...

"...I asked this explicitly and did not get an answer."

I'll take your word for it. I can certainly understand not wanting to invest too much time and effort chasing down a 'free energy/pmm' company at that point in time.

I've been paying attention for a while and I have come to the conclusion that Steorn are a genuine company and that they really believe they have what they say. Of course the jury may find differently, but Steorn thinks they are right. We'll just have to wait for the jury.

Well, I won't take any more of your time. I'm sure you weren't planning on having Steorn forumites invading your blog!

Anonymous said...

@Doug

There are many theories abounding as to the possible scam that could be going on in the comments of multiple blog postings at
http://freeenergytracker.blogspot.com/

Would certainly like to have someone with a bit more technical background involved there and on the official steorn forums.

Kent

Doug Natelson said...

Here are my brief emails exchanged with Steorn. I didn't save the attachments from them, but it was nothing particularly interesting.

Anonymous said...

Doug,

I have just sent you a mail outlining the fact that your question relating to independent labs is answered very clearly. I trust that you will indeed reflect this fact in this blog.

Regards,

Sean McCarthy
Steorn Ltd.

Anonymous said...

Doug,

Thanks for the following update:

Update: Sean McCarthy of Steorn informs me that my comments above are inaccurate, and that, indeed, their evaluation will be based on tests specified by their "jury" in an independent laboratory. My apologies for any confusion. This was not clear to me last fall, and I haven't been following this in the interim.



And just so that there is no further confusion on this matter the jury selection of independent labs and test methods was documented and made clear during the process of application, i.e. this was always the way that it was going to be and applicants were made aware of this fact.

Sean McCarthy
Steorn Ltd.

Anonymous said...

..If Steorns device works, it will be found as a novel way of converting matter to energy. After all, matter is electromagnetic energy in another form,, E=MC2 remember??. There is no violation of COE in that...
Sonoboy

Anonymous said...

Why does everyone (even scientists) forget that free energy does not mean a violation of CoE necessarily.

For example Solar energy is free. That means, no investment is required in terms of energy once a solar cell is built.

There is always a possibility of new untapped energy sources.

Anonymous said...

Doug

Regardless of the outcome of the steorn machine, i think what you are not admitting to is that the steorn challenge failed the "gut check" most scientists use to pursue a subject.
i am a biased observer,But the sense I get is that Steorn flunked the gut check. No one would pass up a world changing Event if they believed it was one.
Right or Wrong?

Doug Natelson said...

Right.