Re: [time-nuts] IEEE Spectrum - Dec 2017 - article on chip-scale atomic frequency reference
On Fri, 15 Dec 2017 17:17:31 +0100 Mike Cookwrote: > > The original paper in question is [1]. As with the nitrogen vacancy > > clocks, which also trap nitrogen within a Carbon lattice, these have the > > drawback of quite high temperature coefficients, Harding et al measured > > 89ppm/K. > > I wonder if Cs-133 can be inserted into C-60 fullerene? If it could, > then a primary reference on a chip might be possible. No, it wouldn't. It isn't the species of atom being used that defines whether it is a primary standard or not, but rather that it is possible to exactly calculate the frequency of the output given all disturbances. It is possible to achieve this with Cs, Rb, Hg, Yb, Sr, ... it just depends on how you do it. The problem with the atom-in-fullerene is that the atom is not in (a good approximation of) vacuum, as it is surrounded by a molecule in close proximity. This means the surrounding atoms disturb the electrons of the probed atom. This is what causes the large temperature dependence. Attila Kinali -- It is upon moral qualities that a society is ultimately founded. All the prosperity and technological sophistication in the world is of no use without that foundation. -- Miss Matheson, The Diamond Age, Neil Stephenson ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] IEEE Spectrum - Dec 2017 - article on chip-scale atomic frequency reference
> Le 15 déc. 2017 à 14:06, Attila Kinalia écrit : > > On Fri, 8 Dec 2017 09:40:29 -0800 > Tom McDermott wrote: > >> Researchers at Oxford U. have fabricated an atomic reference based on >> a single nitrogen molecule inside a 60-atom carbon sphere ("Fullerene"). >> The cage of carbon isolates the nitrogen from external electric fields, >> and they've developed a method to also isolate it from external magnetic >> fields. > > The original paper in question is [1]. As with the nitrogen vacancy > clocks, which also trap nitrogen within a Carbon lattice, these have the > drawback of quite high temperature coefficients, Harding et al measured > 89ppm/K. I wonder if Cs-133 can be inserted into C-60 fullerene? If it could, then a primary reference on a chip might be possible. > > Attila Kinali > > > [1] "Spin Resonance Clock Transition of the Endohedral Fullerene 15N@C60", > by Harding, Zhou, Zhou, Myers, Ardavan, Briggs, Porfyrakis, Laird, 2017 > https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.119.140801 > -- > It is upon moral qualities that a society is ultimately founded. All > the prosperity and technological sophistication in the world is of no > use without that foundation. > -- Miss Matheson, The Diamond Age, Neil Stephenson > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. "The power of accurate observation is commonly called cynicism by those who have not got it. » George Bernard Shaw ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] IEEE Spectrum - Dec 2017 - article on chip-scale atomic frequency reference
On Fri, 8 Dec 2017 09:40:29 -0800 Tom McDermottwrote: > Researchers at Oxford U. have fabricated an atomic reference based on > a single nitrogen molecule inside a 60-atom carbon sphere ("Fullerene"). > The cage of carbon isolates the nitrogen from external electric fields, > and they've developed a method to also isolate it from external magnetic > fields. The original paper in question is [1]. As with the nitrogen vacancy clocks, which also trap nitrogen within a Carbon lattice, these have the drawback of quite high temperature coefficients, Harding et al measured 89ppm/K. Attila Kinali [1] "Spin Resonance Clock Transition of the Endohedral Fullerene 15N@C60", by Harding, Zhou, Zhou, Myers, Ardavan, Briggs, Porfyrakis, Laird, 2017 https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.119.140801 -- It is upon moral qualities that a society is ultimately founded. All the prosperity and technological sophistication in the world is of no use without that foundation. -- Miss Matheson, The Diamond Age, Neil Stephenson ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] IEEE Spectrum - Dec 2017 - article on chip-scale atomic frequency reference
Citerar Mark Sims: In the standards definitions that include "at sea level", the question these days is "which sea level?". As ocean temperature changes sea level will change (except maybe in Washington DC). Will the standards be amended to include something like "at sea level in 1990" or will the value being defined drift around with the changing sea level? From the current Swedish vertical datum. (http://www.lantmateriet.se/globalassets/kartor-och-geografisk-information/gps-och-matning/geodesi/rapporter_publikationer/rapporter/lmv-rapport_2007_4.pdf) "This realisation was made using the Normaal Amsterdams Peil (NAP) as zero level in the traditional European way. [...] It has for instance been questioned whether NAP is the most suitable way to fix the zero level. Is it not better to wait for a so-called World Height System (WHS), which is fixed using GPS and a global geoid model of cm accuracy?" Has the World Height System been agreed/released? http://www.euref.eu/documentation/Tutorial2015/t-04-02-Ihde.pdf Picture showing reference origin for vertical datums in Europe. https://en.wikipedia.org/wiki/File:Vertical_references_in_Europe.svg -- Björn ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] IEEE Spectrum - Dec 2017 - article on chip-scale atomic frequency reference
A 30 cm daily vertical offset is pretty typical. I've seen over 45 cm. Horizontal offsets are usually less than +/- 75 mm per day with the longitude displacement typically twice the latitude displacement. Heather uses a standard model (see http://geodesyworld.github.io/SOFTS/solid.htm) to calculate earth tides. I converted the Fortran code to C and use a more accurate routine for calculating sun and moon positions. The gravity calculation code is from TVB's code. Actual tides experienced at a given location depend can depend upon locally unique factors like underground geology and nearby bodies of water. Compensating altitude for an optical clock would be considerably more complex. --- > You're place really moved a foot in 48 hours? Impressive and scary! ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] IEEE Spectrum - Dec 2017 - article on chip-scale atomic frequency reference
Checkhttps://en.wikipedia.org/wiki/Earth_tide According to that, a foot of motion is easily plausible. The Wiki article says that displacements around a meter in the solid crust can be seen over the right intervals. This must wreak havoc in VLBI geodesy work, except that for some in the field this would be the "signal" and most everything else the noise. Dana On Sat, Dec 9, 2017 at 7:42 PM, Tom Holmeswrote: > Mark... > You're place really moved a foot in 48 hours? Impressive and scary! > > From Tom Holmes, N8ZM > > > On Dec 9, 2017, at 8:19 PM, Mark Sims wrote: > > > > Which gets real fun with things like solid earth tides getting > involved. Lady Heather can now calculate and plot solid earth tides. > Over the last 48 hours my place moved up/down 315 mm and gravity changed > 186 microgals... and that was a rather stable period. > > > > -- > > > >> A 1 meter change in elevation corresponds to a frequency offset of > about 1e-16. So for 1e-18 levels of performance you "only" need to know g, > or your elevation to 1 cm accuracy. > > > > ___ > > time-nuts mailing list -- time-nuts@febo.com > > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > > and follow the instructions there. > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] IEEE Spectrum - Dec 2017 - article on chip-scale atomic frequency reference
Hi Just as there are Time Nuts, there are Tide Nuts (I suppose it’s capitalized …). There is a a lot of data out there on just what sort of solid tides one might see at this or that point. Bob > On Dec 10, 2017, at 7:29 AM, Azelio Borianiwrote: > > Is that a Trimble Thunderbolt? Is there a way to compute the uncertainties? > > On Sun, Dec 10, 2017 at 2:42 AM, Tom Holmes wrote: >> Mark... >> You're place really moved a foot in 48 hours? Impressive and scary! >> >> From Tom Holmes, N8ZM >> >>> On Dec 9, 2017, at 8:19 PM, Mark Sims wrote: >>> >>> Which gets real fun with things like solid earth tides getting involved. >>> Lady Heather can now calculate and plot solid earth tides. Over the last >>> 48 hours my place moved up/down 315 mm and gravity changed 186 >>> microgals... and that was a rather stable period. >>> >>> -- >>> A 1 meter change in elevation corresponds to a frequency offset of about 1e-16. So for 1e-18 levels of performance you "only" need to know g, or your elevation to 1 cm accuracy. >>> >>> ___ >>> time-nuts mailing list -- time-nuts@febo.com >>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >> >> ___ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] IEEE Spectrum - Dec 2017 - article on chip-scale atomic frequency reference
Is that a Trimble Thunderbolt? Is there a way to compute the uncertainties? On Sun, Dec 10, 2017 at 2:42 AM, Tom Holmeswrote: > Mark... > You're place really moved a foot in 48 hours? Impressive and scary! > > From Tom Holmes, N8ZM > >> On Dec 9, 2017, at 8:19 PM, Mark Sims wrote: >> >> Which gets real fun with things like solid earth tides getting involved. >> Lady Heather can now calculate and plot solid earth tides. Over the last >> 48 hours my place moved up/down 315 mm and gravity changed 186 microgals... >> and that was a rather stable period. >> >> -- >> >>> A 1 meter change in elevation corresponds to a frequency offset of about >>> 1e-16. So for 1e-18 levels of performance you "only" need to know g, or >>> your elevation to 1 cm accuracy. >> >> ___ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] IEEE Spectrum - Dec 2017 - article on chip-scale atomic frequency reference
Mark... You're place really moved a foot in 48 hours? Impressive and scary! >From Tom Holmes, N8ZM > On Dec 9, 2017, at 8:19 PM, Mark Simswrote: > > Which gets real fun with things like solid earth tides getting involved. > Lady Heather can now calculate and plot solid earth tides. Over the last 48 > hours my place moved up/down 315 mm and gravity changed 186 microgals... and > that was a rather stable period. > > -- > >> A 1 meter change in elevation corresponds to a frequency offset of about >> 1e-16. So for 1e-18 levels of performance you "only" need to know g, or your >> elevation to 1 cm accuracy. > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] IEEE Spectrum - Dec 2017 - article on chip-scale atomic frequency reference
Which gets real fun with things like solid earth tides getting involved. Lady Heather can now calculate and plot solid earth tides. Over the last 48 hours my place moved up/down 315 mm and gravity changed 186 microgals... and that was a rather stable period. -- > A 1 meter change in elevation corresponds to a frequency offset of about > 1e-16. So for 1e-18 levels of performance you "only" need to know g, or your > elevation to 1 cm accuracy.___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] IEEE Spectrum - Dec 2017 - article on chip-scale atomic frequency reference
Yep, to paraphrase Bunker Hunt's "a billion dollars ain't what it used to be"... a nanosecond (or picosecond) ain't what it used to be. Things that used to be insignificant n'th order theoretical nuisances are now very real significant problems. > But it's not one-to-one as you suggest. A 1 meter change in elevation > corresponds to a frequency offset of about 1e-16. So for 1e-18 levels of > performance you "only" need to know g, or your elevation to 1 cm accuracy. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] IEEE Spectrum - Dec 2017 - article on chip-scale atomic frequency reference
Mark, > In the standards definitions that include "at sea level", the question these > days is "which sea level?". Chris, > So does that mean e.g. NIST and BIPM need to measure the acceleration at > their respective locations to within parts in 10^17 or 10^18 in order to > compare their frequency standards? Yes, all national timing labs do this to one degree or another. To operate and compare clocks at that level of precision you need to accurately know your geopotential, which is sort of like knowing the acceleration of gravity, or elevation. But it's not one-to-one as you suggest. A 1 meter change in elevation corresponds to a frequency offset of about 1e-16. So for 1e-18 levels of performance you "only" need to know g, or your elevation to 1 cm accuracy. > That seems not practical. It is practical, and necessary, and really cool! Here are some papers that will give you an idea how much work it takes to make clocks at the 1e-16 and 1e-17 level. I mean, it's not like you just throw some cesium atoms in a bottle, rub the lamp, and out comes a genie singing 9192.631770 MHz. These two examples describe the complexity of a primary cesium standard: "Accuracy evaluation of the primary frequency standard NIST-7", 2001 http://tf.nist.gov/timefreq/general/pdf/1497.pdf "Accuracy evaluation of NIST-F1", 2002 http://tf.nist.gov/timefreq/general/pdf/1823.pdf In the first paper, see especially tables 1, 3 and 4 for an idea of the corrections they must apply. You'll notice that the largest correction is gravitational. Therefore part of their job in making a primary standard is to measure gravity at the exact point where the cesium atoms operate. And yes, that gets you in the dirty world of what's underground, what mountains are nearby, where's the water table this week, what shape the earth really is, and the phase of the moon, etc. These two examples describe the complexity of precisely measuring gravity in order to calibrate an atomic clock: "The relativistic redshift with 3 × 10−17 uncertainty at NIST, Boulder, Colorado, USA", 2003 http://tf.boulder.nist.gov/general/pdf/1846.pdf "A re-evaluation of the relativistic redshift on frequency standards at NIST, Boulder, Colorado, USA", 2017 http://tf.boulder.nist.gov/general/pdf/2883.pdf Really, all four papers are worth a quick read, even if you just look at the tables and photos. /tvb ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] IEEE Spectrum - Dec 2017 - article on chip-scale atomic frequency reference
Hi If the frequency sensitivity is 1x10^-13 / G you don’t need a lot of precision in your measurement of G. The same issues apply to things like magnetic field and the rest. Bob > On Dec 9, 2017, at 4:02 PM, Chris Caudlewrote: > > On Sat, December 9, 2017 2:39 pm, Magnus Danielson wrote: >> The standard acceleration is internationally agreed at 3rd CGPM in 1901 >> to be 9.80665 m/s^2. > > So does that mean e.g. NIST and BIPM need to measure the acceleration at > their respective locations to within parts in 10^17 or 10^18 in order to > compare their frequency standards? > That seems not practical. > -- > Chris Caudle > > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] IEEE Spectrum - Dec 2017 - article on chip-scale atomic frequency reference
Hi, On 12/09/2017 10:02 PM, Chris Caudle wrote: On Sat, December 9, 2017 2:39 pm, Magnus Danielson wrote: The standard acceleration is internationally agreed at 3rd CGPM in 1901 to be 9.80665 m/s^2. So does that mean e.g. NIST and BIPM need to measure the acceleration at their respective locations to within parts in 10^17 or 10^18 in order to compare their frequency standards? That seems not practical. No, you have a large scale-factor so you really don't need that much of precision to achieve it. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] IEEE Spectrum - Dec 2017 - article on chip-scale atomic frequency reference
On Sat, December 9, 2017 2:39 pm, Magnus Danielson wrote: > The standard acceleration is internationally agreed at 3rd CGPM in 1901 > to be 9.80665 m/s^2. So does that mean e.g. NIST and BIPM need to measure the acceleration at their respective locations to within parts in 10^17 or 10^18 in order to compare their frequency standards? That seems not practical. -- Chris Caudle ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] IEEE Spectrum - Dec 2017 - article on chip-scale atomic frequency reference
Hi, On 12/09/2017 09:13 PM, Bob kb8tq wrote: Hi I suspect that at the practical level, you define standard atmospheric pressure, standard gravity, standard magnetic field ….. and on down the list. At some point “sea level” becomes a redundant expression. The standard acceleration is internationally agreed at 3rd CGPM in 1901 to be 9.80665 m/s^2. So, that is "sea level". See SI brochure, I used version 8 in english, page 143. This is also the standard value I have in my calculators and used for all my acceleration calculations. In practice labs have their contributions into EAL/TAI corrected for their deviation from "sea level" for proper frequency of TAI. Cheers, Magnus Bob On Dec 9, 2017, at 2:14 PM, Mark Simswrote: In the standards definitions that include "at sea level", the question these days is "which sea level?". As ocean temperature changes sea level will change (except maybe in Washington DC). Will the standards be amended to include something like "at sea level in 1990" or will the value being defined drift around with the changing sea level? ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] IEEE Spectrum - Dec 2017 - article on chip-scale atomic frequency reference
Hi I suspect that at the practical level, you define standard atmospheric pressure, standard gravity, standard magnetic field ….. and on down the list. At some point “sea level” becomes a redundant expression. Bob > On Dec 9, 2017, at 2:14 PM, Mark Simswrote: > > In the standards definitions that include "at sea level", the question these > days is "which sea level?". As ocean temperature changes sea level will > change (except maybe in Washington DC). Will the standards be amended to > include something like "at sea level in 1990" or will the value being defined > drift around with the changing sea level? > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] IEEE Spectrum - Dec 2017 - article on chip-scale atomic frequency reference
On 12/9/17 11:14 AM, Mark Sims wrote: In the standards definitions that include "at sea level", the question these days is "which sea level?". As ocean temperature changes sea level will change (except maybe in Washington DC). Will the standards be amended to include something like "at sea level in 1990" or will the value being defined drift around with the changing sea level? Sea Level is arbitrary anyway - what is usually meant is "zero elevation relative to some specified geoid". The Pacific and Atlantic oceans have different mean heights relative to the geoid In the United States, for a long time it was the North American Datum (NAD) that was the reference, but now, it's probably WGS84 (I'm too lazy to go look it up). WGS84 has a very precise definition in terms of the semiaxes lengths, and their orientation relative to stellar references. WGS 84 uses the IERS reference meridian for longitude. Flattening of 1/298.257,223,563 equatorial radius of 6,378,137 m so polar radius of 6,356,752.3142 m The Earth Grav Model (EGM96) defines the geoid, last revised in 2004. *that* model defines the nominal sea surface with spherical harmonics. There's something like 100,000 specific terms in that gravity model. Sourceforge has a program that will tell you geoid height for a given lat lon. https://geographiclib.sourceforge.io/cgi-bin/GeoidEval Near my house (34N, 119W), it appears that the EGM96 height is -37.17 m, relative to the ellipsoid defined above. It so happens that due to crustal movement, my house is gradually rising about 1 cm/year, but I don't know if the local sea level also rises to match, or if the beach is getting farther away. One can measure this, in theory https://www.unavco.org/education/resources/modules-and-activities/gps-california-plate-motion/gps-california-plate-motion.html ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] IEEE Spectrum - Dec 2017 - article on chip-scale atomic frequency reference
In the standards definitions that include "at sea level", the question these days is "which sea level?". As ocean temperature changes sea level will change (except maybe in Washington DC). Will the standards be amended to include something like "at sea level in 1990" or will the value being defined drift around with the changing sea level? ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] IEEE Spectrum - Dec 2017 - article on chip-scale atomic frequency reference
Hi If you dig back into the various papers on the subject (and the proceedings that log the post paper questions) the issue of “can we trust the implementation?” does indeed come up. It’s come up for at least the last 50 years that I’m aware of. The basic argument runs that for fundamental standards, you need to approach the process in different ways. You then compare the results from those different methods. Only after you have done that, do you build confidence in the accuracy of the various processes. Indeed once you have built confidence in a single approach, you may decide to all go with that one approach or implementation. Bob > On Dec 9, 2017, at 12:54 PM, Chris Caudlewrote: > > There is a piece missing for me in the articles I have found on new atomic > standards. > > This is what I (think I) do understand: > Quantum properties of the atoms can be interrogated using various RF or > optical means to servo the frequency of an oscillator (which could be a > laser based optical oscillator). > > The international standard for frequency (based on time) is defined in > terms of a theoretical condition of cesium atoms which cannot be perfectly > achieved in practice, needing absolute zero temperature, > gravity/acceleration equivalent exactly to mean sea level of earth, no > magnetic perturbation, no interaction such as bouncing off of cavity > walls, etc. > > New optical standards can achieve "accuracies" of parts in 10^16, verified > by comparing multiple instances of the standards with each other, and if > the standards are built correctly and the theory of operation is correct, > the multiple separate pieces of equipment should agree in frequency output > to within some parts in 10^x, where x has historically been around 15, but > is now reaching toward 17. > > So far so good, but here is where I have a gap: > I put "accuracies" in quotations above because as far as I understand you > can actually compare consistency of center frequency or stability over > periods of time between two instances of a particular type of atomic > oscillator, but accuracy in the sense of comparing how closely the the > output frequency matches the calculated theoretical output frequency > (assuming that the operating mechanism is fully understood) is going to > depend on having a reference for comparison that is as good or better than > the new standard to be measured. That implies that the reference has > systematic offset that is known to better than parts in 10^17, but that > would require knowing the quantum properties of the atoms in use to that > level, knowing the gravitational potential at your location to that level, > knowing that the temperature dependence of the equipment was below that > level, etc. > > How can anyone ever talk about accuracy in the terms of SI second > definition for these new oscillators? Are they really using layman's > shorthand, and they mean stability and consistency? Or are they really > able to measure all the other factors well enough that they can actually > mean accuracy in the sense of how the SI second definition calls out > absolute zero, gravitational potential, etc.? > > -- > Chris Caudle > > > > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] IEEE Spectrum - Dec 2017 - article on chip-scale atomic frequency reference
So we leave the scientific considerations and delve into the philosophical basis. Somewhere down the line, a standard has to be established, to which all others can be compared. How good this standard is doesn't matter, as long as it's stable. But how does one measure stability? Against what? The fundamental standard is, I think, the revolution of the earth about the sun. Even that is subject to significant perturbations. If one takes, instead, the resonant frequency of a vibrating atom, as you say it is subject to some variation due to its environment. So this elusive number will always remain elusive because of its very nature. Yes, one can refine the measurements, but still some uncertainty will remain. And who was the one who said that all cesium atoms are the same? I suspect each atom is unique, that its mass and charge and natural frequency and so on are different for every atom, even though very close. One could then talk about an average of all cesium atoms but statistically that will only narrow the uncertainty about one order of magnitude. So the answer to your question is, I believe, that there is no answer to your question. Like slaves we are bound to refine our measurements even though we know we can never reach the absolute. I ponder a moment and think, well it's probably about 10 o'clock. I look at the clock and find that I am a few minutes off. I think that's close enough for most of my life. I bought a watch that is about a second a day in error so I find myself resetting it often. I am the only one who cares. Just a few thoughts in passing. Go to the group called Volt Nuts and they go through similar agonies. Bob On Saturday, December 9, 2017, 9:55:00 AM PST, Chris Caudlewrote: There is a piece missing for me in the articles I have found on new atomic standards. This is what I (think I) do understand: Quantum properties of the atoms can be interrogated using various RF or optical means to servo the frequency of an oscillator (which could be a laser based optical oscillator). The international standard for frequency (based on time) is defined in terms of a theoretical condition of cesium atoms which cannot be perfectly achieved in practice, needing absolute zero temperature, gravity/acceleration equivalent exactly to mean sea level of earth, no magnetic perturbation, no interaction such as bouncing off of cavity walls, etc. New optical standards can achieve "accuracies" of parts in 10^16, verified by comparing multiple instances of the standards with each other, and if the standards are built correctly and the theory of operation is correct, the multiple separate pieces of equipment should agree in frequency output to within some parts in 10^x, where x has historically been around 15, but is now reaching toward 17. So far so good, but here is where I have a gap: I put "accuracies" in quotations above because as far as I understand you can actually compare consistency of center frequency or stability over periods of time between two instances of a particular type of atomic oscillator, but accuracy in the sense of comparing how closely the the output frequency matches the calculated theoretical output frequency (assuming that the operating mechanism is fully understood) is going to depend on having a reference for comparison that is as good or better than the new standard to be measured. That implies that the reference has systematic offset that is known to better than parts in 10^17, but that would require knowing the quantum properties of the atoms in use to that level, knowing the gravitational potential at your location to that level, knowing that the temperature dependence of the equipment was below that level, etc. How can anyone ever talk about accuracy in the terms of SI second definition for these new oscillators? Are they really using layman's shorthand, and they mean stability and consistency? Or are they really able to measure all the other factors well enough that they can actually mean accuracy in the sense of how the SI second definition calls out absolute zero, gravitational potential, etc.? -- Chris Caudle ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] IEEE Spectrum - Dec 2017 - article on chip-scale atomic frequency reference
There is a piece missing for me in the articles I have found on new atomic standards. This is what I (think I) do understand: Quantum properties of the atoms can be interrogated using various RF or optical means to servo the frequency of an oscillator (which could be a laser based optical oscillator). The international standard for frequency (based on time) is defined in terms of a theoretical condition of cesium atoms which cannot be perfectly achieved in practice, needing absolute zero temperature, gravity/acceleration equivalent exactly to mean sea level of earth, no magnetic perturbation, no interaction such as bouncing off of cavity walls, etc. New optical standards can achieve "accuracies" of parts in 10^16, verified by comparing multiple instances of the standards with each other, and if the standards are built correctly and the theory of operation is correct, the multiple separate pieces of equipment should agree in frequency output to within some parts in 10^x, where x has historically been around 15, but is now reaching toward 17. So far so good, but here is where I have a gap: I put "accuracies" in quotations above because as far as I understand you can actually compare consistency of center frequency or stability over periods of time between two instances of a particular type of atomic oscillator, but accuracy in the sense of comparing how closely the the output frequency matches the calculated theoretical output frequency (assuming that the operating mechanism is fully understood) is going to depend on having a reference for comparison that is as good or better than the new standard to be measured. That implies that the reference has systematic offset that is known to better than parts in 10^17, but that would require knowing the quantum properties of the atoms in use to that level, knowing the gravitational potential at your location to that level, knowing that the temperature dependence of the equipment was below that level, etc. How can anyone ever talk about accuracy in the terms of SI second definition for these new oscillators? Are they really using layman's shorthand, and they mean stability and consistency? Or are they really able to measure all the other factors well enough that they can actually mean accuracy in the sense of how the SI second definition calls out absolute zero, gravitational potential, etc.? -- Chris Caudle ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] IEEE Spectrum - Dec 2017 - article on chip-scale atomic frequency reference
I saw that about the N atom trapped inside a C60 molecule, but also took note of the present cost of the material. I wonder how much is going to be required to make a good standard. Dana On Fri, Dec 8, 2017 at 11:40 AM, Tom McDermottwrote: > There's an interesting article in the December 2017 issue of IEEE Spectrum. > > Researchers at Oxford U. have fabricated an atomic reference based on > a single nitrogen molecule inside a 60-atom carbon sphere ("Fullerene"). > The cage of carbon isolates the nitrogen from external electric fields, > and they've developed a method to also isolate it from external magnetic > fields. > > They have not incorporated the material into a working standard, but have > licensed the chemical fabrication technology to at least one manufacturer. > The idea is to make a chip-scale atomic frequency reference. > > -- Tom, N5EG > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] IEEE Spectrum - Dec 2017 - article on chip-scale atomic frequency reference
https://www.google.com/amp/s/spectrum.ieee.org/semiconductors/materials/to-build-the-worlds-smallest-atomic-clock-trap-a-nitrogen-atom-in-a-carbon-cage.amp.html > On Dec 8, 2017, at 10:38 AM, Ulrich Rohde via time-nuts> wrote: > > Impressive, Ulrich > > In a message dated 12/8/2017 12:41:23 PM Eastern Standard Time, > tom.n...@gmail.com writes: > > > There's an interesting article in the December 2017 issue of IEEE Spectrum. > > Researchers at Oxford U. have fabricated an atomic reference based on > a single nitrogen molecule inside a 60-atom carbon sphere ("Fullerene"). > The cage of carbon isolates the nitrogen from external electric fields, > and they've developed a method to also isolate it from external magnetic > fields. > > They have not incorporated the material into a working standard, but have > licensed the chemical fabrication technology to at least one manufacturer. > The idea is to make a chip-scale atomic frequency reference. > > -- Tom, N5EG > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] IEEE Spectrum - Dec 2017 - article on chip-scale atomic frequency reference
Impressive, Ulrich In a message dated 12/8/2017 12:41:23 PM Eastern Standard Time, tom.n...@gmail.com writes: There's an interesting article in the December 2017 issue of IEEE Spectrum. Researchers at Oxford U. have fabricated an atomic reference based on a single nitrogen molecule inside a 60-atom carbon sphere ("Fullerene"). The cage of carbon isolates the nitrogen from external electric fields, and they've developed a method to also isolate it from external magnetic fields. They have not incorporated the material into a working standard, but have licensed the chemical fabrication technology to at least one manufacturer. The idea is to make a chip-scale atomic frequency reference. -- Tom, N5EG ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] IEEE Spectrum - Dec 2017 - article on chip-scale atomic frequency reference
There's an interesting article in the December 2017 issue of IEEE Spectrum. Researchers at Oxford U. have fabricated an atomic reference based on a single nitrogen molecule inside a 60-atom carbon sphere ("Fullerene"). The cage of carbon isolates the nitrogen from external electric fields, and they've developed a method to also isolate it from external magnetic fields. They have not incorporated the material into a working standard, but have licensed the chemical fabrication technology to at least one manufacturer. The idea is to make a chip-scale atomic frequency reference. -- Tom, N5EG ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.