Signal detection breakthrough

September 2, 2017 10:01 AM

University of Copenhagen makes low noise breakthrough They make a micro-membrane (with deposited aluminum) that is one side of a capacitor in a resonant circuit. So radio signals at that resonance are *much* larger than the noise floor. They then pick up the radio signal by bouncing a laser off the membrane => radio signal turned into optical "The numbers are impressive. The new device has a room temperature sensitivity of 5 picoVolts per (Hz)^1/2 at a frequency of 1 Mhz. In other words, it does the same job at room temperature that physicists could only dream of doing at the temperature of liquid helium."
posted by aleph (12 comments total)

Just the description reminds me wasn't there that other project that detected sound waves in a room with light, through a potato chip bag? And the system was sensitive enough to detect and extract people's voices. And this is like a shrunk/scaled version of that idea.
posted by polymodus at 10:31 AM on September 2, 2017

That 'laser bounced off a vibrating object' is a 50 year old spying technique, but it is for sound, not radio waves.

I love reading about breakthroughs like this. Then I get impatient and want to know when our cell phones will get much stronger signals in desolate areas.

Then I realize that these early breakthroughs usually end up having lots of problematic roadblocks when trying to turn them into practical applications, usually resulting in decades of delay, after which society ends up forgetting about the breakthrough in the first place.
posted by eye of newt at 11:02 AM on September 2, 2017

-180dBmV
posted by Chuckles at 11:02 AM on September 2, 2017 [3 favorites]

I wonder if this would introduce a different kind of noise once it finds its way into radios and cellphones etc. I imagine you'd start picking up more faint signals from further away and you'd have to improve techniques to sift through them and find the one you're interested in. Probably easier with digital signals than with, let's say, FM radio stations.
posted by Hairy Lobster at 11:16 AM on September 2, 2017

Today, Tolga Bagci at the University of Copenhagen in Denmark and a group of pals demonstrate a device that detects ultra-weak radio waves in an entirely new way.

"a group of pals"?
posted by jedicus at 11:17 AM on September 2, 2017 [1 favorite]

"July 22, 2013"
posted by axiom at 11:20 AM on September 2, 2017 [1 favorite]

I still need to read the details, but if the press release is correct, this sort of thing would be a massive deal for NMR spectroscopy (and MRIs).

Hm, though: the paper they cite is this (paywall), from Nature in 2014.
posted by steady-state strawberry at 11:20 AM on September 2, 2017

So, does this mean we might be able to hear from Voyager just a bit longer?
posted by Thorzdad at 1:55 PM on September 2, 2017 [3 favorites]

Excellent.
posted by Segundus at 1:56 PM on September 2, 2017 [4 favorites]

Is it bad that the first "oh shit" application I thought of was Tempest/van Eck eavesdropping?
posted by fings at 2:07 PM on September 2, 2017 [1 favorite]

This device reduces/prevents noise generated internally in the receiver circuitry. Cell phones and such are mostly limited by external noise, that is ambient noise and interference in the rf spectrum they use.

Think of it this way: a more sensitive microphone doesn't help much when you're recording in a noisy room. But this new technique will help radio telescopes because they're extremely directional, they operate in protected parts of the rf spectrum, and often they are located in "quiet" places (e.g. Green Bank, WV).
posted by ryanrs at 9:44 PM on September 2, 2017

Yes, it's impressive but there's a limited range of applications that can benefit from this one component out of many no longer being a limiting factor in one - admittedly fundamental - regard.

Information happens when you can distinguish a signal from noise - and that's as fundamental a statement as E=mc². Noise comes from everywhere, and when you're working out the limit at which a system can detect a signal you take all the noise from all the bits and add it up alongside the amplification factors. Having a low noise detector is great, because detectors tend to come before further amplification so even a little noise added by them can be a big deal. But you have other components before the detector too, which are usually the most important factor for system noise. (So it won't extend Voyager's lifetime; we'd have little trouble talking fo Voyager for much longer than we' going to, even with today's gubbins, but its going to run out of useful power long before this becomes an issue.)

It can happen that actually, making one component much better opens up new applications or methods that just weren't possible or thought of before, and that's always exciting, so I wouldn't rule that out. Mostly, it doesn't. We already have insanely good signal extraction systems - LIGO, for example - so one of the questions for any new component like this is, does it reduce cost enough to broaden the applicability of what we do already? It's another useful component for imaginative physicists, engineers and system designers, but what it means for the future... have to wait and see. Which makes for a less thrilling press release.
posted by Devonian at 5:12 AM on September 3, 2017 [2 favorites]