It's basically a fancy receive-only radio antenna that can be tuned to any frequency.
Normal antennas are great, but it's very difficult to make them work over more than one "octave", e.g., 1-2 Ghz or 2-4 GHz. A single Rydberg sensor can tune from 1-40 GHz no problem.
The Rydberg sensing element is a glass tube filled with gas. You use one laser to excite the gas into a state that's sensitive to radio waves. You query the sensor with a second laser, whose wavelength sets the radio carrier frequency of interest.
You can set it up as a spectrum analyzer or even coherently demodulate an IF or I/Q signal. But the fundamental advantage is tunability.
From reading "Quantum-Limited Atomic Receiver in the Electrically Small Regime" (PDF) [1], it seems there are 3 main advantages to Rydberg sensors, wide frequency rage (DC to Ghz), very small sampling volume, and non-interaction with the RF fields.
The wide frequency range means that you can use the same sensor for a wide variety of measurements, calibrating it down near (or at) DC, and later using it to make accurate measurements of RF or Microwave signals.
The small sampling volume means that you can probe at resolutions far smaller that the wavelength of the frequencies being measured, so you can measure the field strength in 3d (with appropriate mechanical scanning hardware) of antennas and other gear, something you can't do normally, because normal antennas are much larger than a wavelength.
The isolation means you can effectively probe almost any system and without disruption. Unlike measuring voltages with a voltmeter, there are literally no conductive elements that would reflect or refract RF signals, short out dc signals, or induce currents from present magnetic fields.
> How many 4 or 2 Mhz antenna/transceivers are necessary to sufficiently cover a 0 to 1 Ghz (0 to 1000 to 1000000 Mhz) band? What about to cover 1 Thz: (terahertz) band(s)?
> How should they be placed in spacetime to minimize signal loss e.g due to crosstalk and cost?
Like an antenna, a Rydberg sensor can detect incoming radio signals. Otherwise, the underlying physics are completely different. If there's a way to make it transmit, I've never heard of it.
* What is the difference between a Rydberg atom, an Ion trap, and a Quantum Dot?
These are all unrelated devices with different underlying principles.
* How many 4 or 2 Mhz antenna/transceivers are necessary to sufficiently cover a 0 to 1 Ghz band? What about to cover 1 Thz: (terahertz) band(s)?
It depends what you mean by "cover".
Rydberg sensors are tunable over a huge range, typically quoted up to 20-40 GHz. So one sensor would "cover" the whole range of you're willing to wait.
(I don't know what currently sets that upper limit, but what are you doing that needs more than 40 GHz? Electronics capable of handling such frequencies are rare, specialized, and expensive.)
That said, the instantaneous bandwidth of a Rydberg sensor is low, typically around 1 MHz. So if you want to "cover" the whole 0-1 GHz range all at once, I'd start from a different approach.
* How should they be placed in spacetime to minimize signal loss e.g due to crosstalk and cost?
No idea. Each Rydberg sensor requires a lot of expensive support equipment, including two or more precisely tuned lasers.
> Like an antenna, a Rydberg sensor can detect incoming radio signals. Otherwise, the underlying physics are completely different. If there's a way to make it transmit, I've never heard of it.
> * What is the difference between a Rydberg atom, an Ion trap, and a Quantum Dot?
> These are all unrelated devices with different underlying principles.
Ion traps as used in Trapped ion quantum computing involve particles whose wavefunctions are read and written.
Typically trapped ion QC systems are designed to minimize loss and interference. Visible photonic (and other) spectral emissions are certainly caused by changing the wave functions of particles with waveguided EM with and without an additional beam as a waveguide. Is a third beam necessary or useful for modulating particle wave state?
Quantum Dots have spectral emissions due to applied fields.
Quantum Dots are useful as sensors for photonic and other bands.
Rydberg atoms' outer electrons are measurable like Hydrogen electrons.
>> Within the 21st century defect centres in various solid state materials have emerged,[9] most notably diamond, silicon carbide[10][11] and boron nitride.[12] the most studied defect is the nitrogen vacancy (NV) centers in diamond that was utilised as a source of single photons.[13] These sources along with molecules can use the strong confinement of light (mirrors, microresonators, optical fibres, waveguides, etc.) to enhance the emission of the NV centres. As well as NV centres and molecules, quantum dots (QDs),[14] quantum dots trapped in optical antenna,[15] functionalized carbon nanotubes,[16][17] and two-dimensional materials[18][19][20][21][22][23][24] can also emit single photons and can be constructed from the same semiconductor materials as the light-confining structures. It is noted that the single photon sources at telecom wavelength of 1,550 nm are very important in fiber-optic communication and they are mostly indium arsenide QDs.[25] [26] However, by creating downconversion quantum interface from visible single photon sources, one still can create single photon at 1,550 nm with preserved antibunching. [27]
The above linked article describes DNA-based quantum dots.
> *How many 4 or 2 Mhz antenna/transceivers are necessary to sufficiently cover a 0 to 1 Ghz band? What about to cover 1 Thz: (terahertz) band(s)?
> It depends what you mean by "cover".
> Rydberg sensors are tunable over a huge range, typically quoted up to 20-40 GHz. So one sensor would "cover" the whole range of you're willing to wait.
> (I don't know what currently sets that upper limit, but what are you doing that needs more than 40 GHz? Electronics capable of handling such frequencies are rare, specialized, and expensive.)
DSS Digital Spread Spectrum and OFDM Orthogonal Frequency Division Multiplexing use multiple frequencies for transmission (of ~"wave packets") concurrently.
IDK, particle collider sensors that need to monitor for shift across wavelength, phase, and amplitude.
("This means that hard-to-measure optical properties such as amplitudes, phases and correlations—perhaps even these of quantum wave systems—can be deduced from something a lot easier to measure: light intensity."https://news.ycombinator.com/item?id=37226121#37226160 )
Don't e.g. radiotelescopes already cover wider ranges of frequencies than 1 Mhz? The visible colors span more than 1 Mhz.
>> Terahertz radiation is electromagnetic radiation with a frequency between 0.1 and 10 THz; it falls between radio waves and light waves on the spectrum; it encompasses portions of the millimeter waves and infrared wavelengths. Because of its high frequency and short wavelength, terahertz wave has a high signal-to-noise ratio in the time domain spectrum.[1] Tomography using terahertz radiation can image samples that are opaque in the visible and near-infrared regions of the spectrum.
> That said, the instantaneous bandwidth of a Rydberg sensor is low, typically around 1 MHz. So if you want to "cover" the whole 0-1 GHz range all at once, I'd start from a different approach.
Is there a bus that can record e.g. 10 Tbit/s of random? So, the task is to do EM ADC/DAC to/from optical fiber?
> *How should they be placed in spacetime to minimize signal loss e.g due to crosstalk and cost?*
> No idea. Each Rydberg sensor requires a lot of expensive support equipment, including two or more precisely tuned lasers.*
The linked article above describes a low cost integrated laser that would probably work for trapped ion quantum computing and also Rydberg sensors:
Get them all! (And filter out bands per legal regulations)
Is it that there need to be 1000x 1 Mhz antennae to monitor for a whole band (linear scaling), or are there potential efficiencies in addition to reducing the cost and size of the electron trap and the laser(s)?
IIUC integrated laser + this [1] is almost a QC platform and accidentally a transmitter if nonunitary in an open system.
[1] "Photonic chip transforms lightbeam into multiple beams with different properties" "Universal visible emitters in nanoscale integrated photonics" (2023) https://news.ycombinator.com/item?id=36580151
That was my first impression, but having worked on the forefront in this area a decade ago, I expect that it's real. The technology exists, and it's now been around long enough to become generally available.
I meant what little content they had on their site was Marketing BS, not the actual technology... in retrospect I should have edited my comment to be much clearer.
It's hard to understand what this is actually for. Does anyone have an ELI5 for this?
Info on a Rydberg atom is on wikipedia
https://en.wikipedia.org/wiki/Rydberg_atom