[HN Gopher] Rydberg atoms detect clear signals from a handheld r...
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Rydberg atoms detect clear signals from a handheld radio
Author : Brajeshwar
Score : 66 points
Date : 2026-02-27 17:07 UTC (2 days ago)
(HTM) web link (phys.org)
(TXT) w3m dump (phys.org)
| boznz wrote:
| Interesting, I learnt something new today. My only comment was
| the noise floor of the simple graph was very high-25dBm which
| (without having a clue how the physics works and skimming the
| article) sounds about right for something with no proper RF
| front-end.
| Neywiny wrote:
| Where do you see -25 dBm noise floor? But chance do you mean a
| 25 dB SNR?
| boznz wrote:
| The picture here
| <https://scx1.b-cdn.net/csz/news/800a/2026/rydberg-atoms-
| dete...> though I just saw the X-axis refers to audio
| frequencies, kind of confusing on first glance.
| Neywiny wrote:
| That's dB not dBm, and the article says it's normalized to
| whatever power each of the two options received at. Nothing
| about absolute power.
| amelius wrote:
| What modulation technique?
| hausen wrote:
| Considering the mention to Family Radio Service, most likely
| they're demodulating FM.
| m3047 wrote:
| "The key here is that the radio frequencies used in handheld
| radios are far from the natural resonances of the atom, so
| while the atoms can sense the radiation, they don't respond to
| the frequency modulation on which the audio is encoded,"
| rwmj wrote:
| That raised the question, how do you make Rydberg atoms, and the
| answer is (always!) with lasers:
| https://en.wikipedia.org/wiki/Rydberg_atom
| rkagerer wrote:
| _We demonstrated simultaneous reception of neighboring channels
| with strong isolation between them. " This enabled the
| researchers to monitor numerous radio channels at once, instead
| of tuning into them individually._
|
| Can anyone elaborate on this? How does a single receiver produce
| multiple concurrent outputs, and how are they isolated in this
| context?
| amelius wrote:
| I have no clue, but I would guess that they do not have a
| single atom but rather an entire crystal of them.
| jacquesm wrote:
| Because all of the signals are superimposed. So if your
| receiver isn't selective it will show all of them at once and
| if you then demodulate selective parts of the spectrum by
| filtering you can isolate the signals individually.
|
| Think of any antenna: it is just a rod or a coil, it may have a
| specific frequency that it particularly likes because that is a
| nice fraction of its wavelength or close to its own resonance
| frequency, but that doesn't mean it isn't going to receive all
| the other signals to greater or lesser extent as well. The
| ratio between that one that it likes and the rest is called
| selectivity. The lower the selectivity the more evenly you will
| receive all signals at the same time.
|
| Usually receivers have a tuned front-end to get as much of the
| signal you want and to repress the rest as much as possible but
| that is optional, you can have a wideband front end just the
| same.
| richk449 wrote:
| Unlike conventional cars that require expensive safety systems
| such as air bags and seat belts, the mover3000's top speed of
| one mile per hour makes it intrinsically safe.
| ElProlactin wrote:
| A company called Infleqtion already has an RF sensing product
| that uses Rydberg atoms.
|
| https://infleqtion.com/quantum-rf-receiver/
| jacquesm wrote:
| Is it really a product already? There are a number of renders
| but the 'products' link does not work for me.
| ElProlactin wrote:
| Not sure if it's being "actively" used in real-world
| deployments yet, but it does exist.
|
| https://www.prnewswire.com/news-releases/infleqtions-
| quantum...
| jacquesm wrote:
| Ok, I found a video:
|
| https://www.youtube.com/watch?v=j18K7MZdyY8
|
| That looks like it is definitely real but also extremely
| fragile and there is no mention of any performance specs.
| But that's 3 years old now and no product(s) available yet.
| numpad0 wrote:
| That page uses the older versions of "SWaP-C2 Optimized[1]"
| meme, I would guess it might have not been updated in 3-5
| years.
|
| 1: Stands for "Size, Weight, and Power [and] Cost [and]
| Cooling Optimized", defense industry equivalent of self
| awarded gold medal stickers on product packaging, apparently
| jacquesm wrote:
| Oh, that's very neat, I can imagine that some future front-end to
| a SDR will have no antenna at all, just a bunch of solid state.
|
| The abstract of the paper:
|
| """Coupling a Rydberg vapour medium to both microwave and optical
| fields enables the benefits of all-optical detection, such as
| minimal disturbance of the measured field and resilience to very
| strong signals, since no conventional antenna is required.
| However, peak sensitivity typically relies on adding a microwave
| local oscillator, which compromises the all-optical nature of the
| measurement. Here we introduce an alternative, optical-bias
| detection, that maintains fully optical operation while achieving
| high sensitivity. To address laser phase noise, which is critical
| in this approach, we perform a simultaneous measurement of the
| noise using a nonlinear process and correct it in real time via
| data processing. This yields a 35 dB improvement in signal-to-
| noise ratio compared with the basic method. We demonstrate a
| sensitivity of 176 nV / cm / sqrt(f Hz) , reliable operation _up
| to 3.5 mV /cm at 13.9 GHz_, and quadrature-amplitude modulated
| data transmission, underlining the ability to detect microwave
| field quadratures while preserving the unique advantages of all-
| optical detection."""
|
| Emph. mine, at about -36 dBm that's not super sensitive yet
| though, but that formula suggests that at lower frequencies it
| should be a lot more sensitive.
|
| The paper is at:
| https://www.nature.com/articles/s41467-025-63951-9
| fsh wrote:
| The abstract is not very clearly written. The 3.5 mV/cm is the
| maximum detectable field strength before the system starts to
| saturate. I would be interested how the sensitivity compares to
| conventional (cryogenic) semiconductor detectors.
| jacquesm wrote:
| Ah, yes, you are right, I misinterpreted the part the maximum
| was aimed at, thank you for the correction.
|
| And I too am interested in a like-for-like setup with the
| best of what is currently on offer as the benchmark.
| peter_retief wrote:
| I immediately thought of the old crystal radios and a short
| search brought up this comparison. While old radios used a
| natural mineral (galena) to detect radio waves, modern Rydberg
| radio receivers use a synthetic photonic crystal (often made of
| silicon or glass) to guide and enhance the radio signal for
| improved performance.
| peter_retief wrote:
| https://www.mpg.de/9142418/magnetism-in-artificial-crystal and
| this
| jacquesm wrote:
| That's not the function of the crystal though, it is not
| optical but 100% electrical and serves to demodulate the
| signal, not to receive it.
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