This really shows the marvel of HP being able to convert physics experiments to a useful product that can be calibrated with standard equipment and by people without a Nobel prize in their pockets. Your explanation is super clear. You were able to explain enough of the details so us noobs can understand what is going on.
Excellent discussion! I was happy to see the 5334B Frequency counter in the video as I was the Service Engineer for that product and designed the self test and service strategy for it.
Awesome! I love that counter, it’s my primary instrument below 1.5 GHz. I have the high stability oven oscillator in it and calibrate it once a year with the Cesium. It stays pretty much on target.
@@CuriousMarc Hopefully the service manual for that counter is dramatically simpler than the 5061. I went to great pains to have the unit troubleshoot itself from known good kernal out to the edge circuits. Most of the testing (assuming the microprocessor is alive and the power supplies work) is just hooking it's outputs up to it's inputs and running it through it's various switching paths. It doesn't require a lot of external test equipment to test and calibrate it. This also greatly simplified the amount of production test equipment needed on the manufacturing line to test it out. I got a nice internal award for that. This was way back in 1980 IIRC so I'm glad you are getting good use out of it.
@@brianbeasley7270 Just out of interest, do you know any of the people that worked on the HP53131/2A? I've always wondered what the story behind the genuinely awful standard oscillator in those counters was - I suspect it has to be accountant related, since I can't see the engineers being exactly happy with shipping a product with a borderline unusable internal timebase.
@@TrimeshSZ Sorry, I didn't know any of them. That was after I left the division. It was most likely a low cost oscillator for the time to lower the price. Sorry it wasn't up to standards!
@@brianbeasley7270 Well, it just meant you had to use an external ref or get the (excellent) high or ultra-high stability options - it was just that a 5 part in 10^-6 oscillator was not what I expected to find in a 10/12 digit/s HP counter!
When I studied engineering the quality of the lecturer absolutely steered my appreciation and interest in a particular subject, you have that gift, I dont know what you do professionally but if you dont lecture or teach its a waste.
My electrical engineering internship was in the Time and Frequency Division at NIST, Phase Noise Measurement group, '93-97, just down the hall from the NIST-7 cesium beam standard. 25 years later, after working in RF communication systems and test equipment, I recently started working at ColdQuanta on quantum computers based on laser cooled neutral Cesium atoms. Your explanation of Zeeman splitting, and demonstration of the tuning, really helped my understanding of clocks and MOTs. I know many of these concepts as absorbed facts I can regurgitate, without much intuition. It also gave some more insight into the march from parts in 1e14, to 5e-15 of NIST-7, to 1or2e-16 of NIST-F2. And, it's one thing to see an Allen Deviation chart of an atomic clock (or a wandering OCXO tone on a SPA), but watching atomic clock drift on an o-scope made it come alive. And fun fact, the gravitational redshift at Earth’s surface corresponds to a fractional frequency gradient of -9.8(2.3)×10-20/mm (at that particular lab in Boulder). With Strontium optical lattice clocks at the 1e-21 level, geopotential uncertainty is the dominate error term. It's fascinating to see all the metrology/sensing that atomic clocks play a huge role: magnetic fields, gravity, inertial navigation, Josephson voltage standards, atomic physics, astronomy, electric fields, mass..... arxiv.org/ftp/arxiv/papers/2109/2109.12238.pdf
18:00 Actually, that was very clear. Best ever. I found myself wishing you had chosen *not* to skip some of the details e.g. how the C-field disallows certain transitions. Very, very satisfying learning. Thanks.
I had dropped the relativity course in university due to getting lost and it being an optional course of luxury. I appreciate the review and explanation!
@@johndododoe1411 No, nice instruments from the 1960’s. But good optics don’t get obsolete nearly as fast as electronics. Still very good instruments today.
At this level even having 3 clocks or (horrors) any odd number of clocks you're still not sure what time it is. You just maybe, statistically, get a better guess. {^_-}
Atomic physicist here - great explanation overall! Here's some additional information about selection rules: The 'selection rules' you mentioned are determined by the polarization of the light - the applied magnetic field matters, but only indirectly. If you (arbitrarily) choose any fixed direction in space, you can define your m_F levels to have fixed total angular momentum projection along that direction. If the polarization of the interrogation laser is aligned with this direction, then we call it 'pi-polarized' and it can only drive transitions that do not change m_F. Note that the definition of the m_F levels depends on your choice of quantization axis. The clock would still work perfectly in exactly zero B. At finite residual B, however, population will begin to be transferred between different m_F levels, unless the B-field is perfectly aligned along your preferred axis. The role of the C-field is to reduce the effect that stray fields have on the angle of the total B-field with respect to this axis. (Simple picture: moving the end of a meterstick by 1 cm changes its orientation much less than moving the end of a 30cm ruler by 1 cm.) An alternate view (equivalent in any nonzero B field) is to choose the direction of the B-field as your quantization axis. Then it's the impurity of the laser polarization projection (along the B-field axis) that causes the unwanted transitions to occur. This has the advantage of ensuring that the corresponding m_F levels are so-called 'energy eigenstates' of the full Hamiltonian, including the Zeeman interaction - but at the expense of more complex selection rules. But either way you do the computation, you get the same result - the component of the B field perpendicular to the light polarization must be zero, or you will get unwanted frequency components.
Here I am learning about NMR spectroscopy in ochem 2, deciding to take a break with an exciting new CuriousMarc video, and getting most of the lecture theory explained back to me (plus a lot more.) No complaints though. Fascinating video. Thank you all for what you do and for taking the time to document it
Back in the early 60's NMR was the latest thing never realized how that experimental lab instrument would change chemistry. I had a medical MRI a few years back and got curious how they worked, most fascinating.
It's amazing how many 'explanations' for the clock are 'it measures hyperfine transitions of cesium.' And are as long if not longer than this video. It's like telling you how a car works: 'it makes gasoline explode.' Excellent work. You've done a great job especially on elements that are hard to grasp in text. I don't think people really appreciate the scale of these measurements. The leap from theory to a practical machine is almost unreal.
I opened this channel and looked at the picture. OMG this guy found a pair of HP Cesium clocks. When I was working with HP, I sold two of them. Both went to Lockheed. After delivery I never saw them again. In those days they were accurate to within one second in 200,000 years. Better accuracy now.
The only thing better than this episode is the fact that I understood exactly what you were doing and explaining! I wish I had some of that test gear, and one of those beautiful clocks! Thank you Marc and Team for another amazing experience! I can't wait for the time dilation clock check!
That was an excellent and very good explanation of the C-field and why it is required. Thank you for another outstanding video. I've never understood why this channel sits under 150k subscribers, it's content and quality is outstanding every time.
The HP 5518A heterodyne laser Interferometer also uses Zeeman effect to split HeNe laser light into 2 opposite polarized beams, with a few MHz difference in frequency, so that the receiver can tell, if the measurement mirror is moving towards or away from receiver. Another instrument with lots of HP magic inside, can measure absolute distances in nm range or flatness of surface plate very accurately.
that's also how they found the incredible G wave. LOL talking about a 10 to the -21 signal. They found something but I don't think it has anything to do with quadrupole gravity waves
Here I am on the last steps of restoring and adjusting a french turn of the century mantel clock to + - 10 minutes PER DAY and super happy with that, and these guys adjusting to the billionth decimal a cesium clock.
I should adjust my best crystal clock, in a HP 5360A frequency counter. The manual suggests adjusting it against WWV. Only about 5 powers of ten worse then this cesium clock.
I remember when I was a kid in 70s, I saw a TV science program which was about relativity, time and speed of light. They used two atomic clocks like those here. They put one in a NASA airplane and another one on the ground. After the airplane did a couple spins the atomic clocks showed some difference about a few nanoseconds. Then the funny guy placed his twin brother in an spaceship which traveled at the speed of light. After a couple minutes, he came back to Earth and he found his brother pretty old. They said the story wasn't a science fiction at all and it was very amazing for me. Perhaps the best science program I ever saw on TV in those years.
Every time a video is posted, I am amazed at what is presented. I would have bet money that 2 HP atomic clocks were not operable at this late date. Those tubes are not replaceable anymore.
I wonder if a vector voltmeter such as the HP 8508A or 8405A might not be a better instrument for detecting minute phase drifts between clock signals. They offer phase resolution down to 0.1deg, which would be difficult to resolve with the oscilloscope. They might also be less susceptible to drift or jitter in the triggering point as compared to an oscilloscope.
What a fantastic video, Marc and the guys on top form. I love the amount of work that went into explaining the somewhat complicated (understatement of the year) quantum physics - Marc, you're a hero.
That's a very nice demonstration and explanation of the Zeeman effect and the magnetic alignment of the HP5061. I've never seen that before in such a detail. Anyhow, I suggest to do frequency comparisons (Cs vs Cs or vs GPS) by time-nuts methods. That is a phase comparison method by means of a high resolution T.I. counter, like your HP5334A. By using John Miles free TimeLab program, which might directly support your counter over GPIB, you can make comfortable stability (Allan Deviation) and uncertainty measurements down into the 10^-13 region, over many hours. That is required to overcome short / medium termed jitter especially of the GPS reference. Easy to accomplish, and maybe making a nice next video.
The main thing to demonstrate is that timekeeping is affected by gravity. If one of the clocks is elevated above the other by a few meters, it should be able to observe that it gradually gains time on the one positioned below it. Even with just one working cesium clock, the GPS reference time can play the role of the baseline clock.
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Now they just need couple of business jets to fly around the world.
Keeping one clock at sea level, and the other up a mountain, should produce a measurable difference. Of course, that means finding a way to make one of the clocks portable, but I think HP was thinking of that when they built these things.
Fascinating. I wish you’d been a lecturer whilst I was at university. You’re a natural! Very clear, and your enthusiasm for the topic is infectious. This is a wonderful example of engineering as the application of science to a problem. Kudos to the HP engineers.
I wish you had been my quantum mechanics teacher during my physics degree. You’re speaking directly to me when you express the theory intertwined with the experimentation and engineering utilization of the phenomenon. What an 18min!
me: forgets about daylight savings time and doesn't even notice for a day or two marc: my cesium clock is 0.0000000001Hz out of spec and we need to calibrate it.
Very cool!!! Avoid brain twisting explanation you ask, NEVER! Thank you so much for sharing all this with us! I grew up around engineers, listening to your explanations give me a warm feeling of being home again. Fascinating stuff. By far my favorite episode on this channel. What could be more mysterious then time? Liquid gold!
This video series really helps me appreciate 100 years of progress in the science of quantum physics. As a career EE it is also fascinating to learn how a thorough understanding of quantum physics led to the creation of a very precise frequency reference which could be manufactured in the 1960/1970’s era and (with calibration) still meet its specs many years later. I own a few vintage HP instruments myself but nothing in the “atomic clock” category. My collection includes a 412A DC VTVM and a 3456A 6.5 digit DVM which both function very well. I frequently use them. Neither required extensive restoration. I found my 412A many years ago in a junkyard/recycling center with its mains power cord and probe leads cut off. It was free for the taking. I picked it up mainly because it looked cool in a very retro way. I never expected it to be functional. But out of curiosity 2 years ago I decided to see if I could get it to work. I was rather surprised to find no faults or issues beyond needing to replace the missing cables and probes. All of its capacitors and vacuum tubes tested good. The optical chopper still worked. I love it’s 100 meg input resistance for DC voltage measurement. It also works very well for Ohms measurement. The 3456A was an eBay find which needed only the replacement of some electrolytic capacitors in its power supply. I also have an 8660C frequency generator which partially works but needs to have the bandpass filters in the 0-100 MHz plug-in rebuilt. Keep up the great videos please!
I watched this video shortly after waking up and I still managed to follow your explanation of the hyperfine energy levels and Zeeman lines. Excellent job at communicating it clearly! You've now inspired me to dig into the literature on magnetic quantum numbers and selection rules, since that's a level of detail that I've only ever heard of in passing before. It's good to have a practical application to tie the knowledge back to.
Marc, you guys should really get in touch with Tom Van Baak for your journey with cesium clocks and precision time keeping. His collection is probably second only to NIST itself.
Ha, that is why I got my second Rb oscillator. I could see a difference between my first Rb and the GPS disciplined oscillator but I didn't know which. With two Rb oscillators I could see the GPS was the issue. It needed a better antenna, small dropout on the GPS would slightly skew the PLL slightly.
Fascinating material and well explained. HP machine designers were in a class of their own. And most still operate as designed. I have several test machines from the 70’s and 80’s that still work as intended.
It's CuriousMarc lecturing on physical chemistry and quantum physics, and it's so cool! You laid out the spectral lines better than any professor at my university when I studied chemistry. Makes me wish I watched this video in 2007 or so. Zeeman's lab gear and experiments (and that stained glass too)? Definitely great and brilliant in its simplicity! Coming up with it was the hard part, doing actual experiments is straightforward, with no multi-million-yankee-bucks worth of equipment. Makes me wonder if there's still some science to be done that doesn't require very advanced and expensive technology. That HP scope is nice, but fades in comparison with Usagi's HP 150A :) So, any video on NMR, EPR or (unrelated, but close) mass spectrometry? That would be great. I was taught the theory of operation and how to interpret the spectra (and determine the structures), but never worked on a NMR or mass spectrometer myself. Nice watch too.
Wow! This was just fantastic, I finally feel like I understand what the SI unit for 1 second actually means. A concrete example with HP cukcoo clocks and everything :D
When comparing the beam current after C-field adjustment hasn't the "beam I-meter" pot been adjusted to keep the maximum on scale when adjusting the amplitude of the audio oscillator, so couldn't that explain the beam current reduction post-adjustment? Not having a 5061 to hand I seem to remember that one just adjusts this so the beam current reads 20 in operation.
Fantastic. I was thinking about an experiment which would be possible in the basement without too much expense. How about verifying the speed of light in different mediums?
I knew a lot of this from studying physics, but I still watched all of it because I found the explanation from an instrument/technician’s perspective to be an interesting change from the atom’s-perspective way I was taught it. All the same components of course, just a different reference frame.
I certainly didn't skip ahead ! I find it fascinating ! Getting some sort of glimpse of what is the fine structure (difference of energy levels dependin on spin) and the hyperfine structure (when applied inside a magnetic field) - and how this applies to define a constant for time (or rather the measurement of time within a reference frame) - and then how it this all applies to the real world.. and so how it really works and how it is calibrated and how it can be done.. (I didn"t understand 10% of it, but it's fascinating nonetheless)
Fantastically clear explanation of both the underlying physics and the calibration process. I feel like I actually understand how cesium clocks work now!It’s beautiful the way you can use very pedestrian lab equipment to calibrate an instrument to deliver time accuracy on the order of 10^-13. What an absolutely brilliant device! Next up: Cesium fountain clock? 😉 BTW: What’s the lifetime of the cesium tube? Does the cesium somehow recirculate, or does it eventually get used up and the tube needs to be replaced?
As I'm watching this I realise that the c field is like the heater in a oven crystal clock, kinda, The magnetic shielding is like the insulation on a oven crystal clock as well, Block out/insulate as much as possible, and then provide your own standard/reference above what still leaks in (out in the case of oven clocks but still, I think this analogy is almost perfect)
Absolutely amazing video as always Marc! You are so lucky to have access to not one but two of those clocks! I managed to get hold of an old rubidium reference module from an aircraft but haven't done anything with it to make it into a useful reference yet. Even when I do it'll be way less accurate than those big boys hehe
@@craigs5212 I shall look into that 😁 at present I bypassed the fried power supply and verified the internal stuff was still working, but then put it on the shelf with various other projects I've not finished yet 🤣
I hope the 'maybe' at the end was not a threat ;-). Thank you Professor Marc for this wonderful Monday morning lecture. Although all of the quantum stuff goes way above my hat I could grasp the overal gist of your explanation. I also never could have surmised two of my fellow countrymen (whose names I once found in a Dutch science museum) would be mentioned in your famous lecture. Wonderful video and looking forward to your 'dual Cesium clock experiment' :o)
It would be super cool to see you repeat the Hafele and Keating time dilation experiment. Also expensive I would imagine! You need a pretty long flight to get results in the nanoseconds. It would be fascinating to try to predict the results of the experiment beforehand and see how it plays out in reality.
When Marc starts the elevator music, time to grab the popcorn and pay attention! IMHO, the best part of the videos. Now to see what @MarcoReps has cooked up.
Now you have 2 clocks you are uncertain again. You now need to get another 3, so you have a cluster of 5, so that you can use the average to get the error from the outliers, and use that average to both get the right time, and also verify all 5 are operating correctly.
While they are able to block the earth's magnetic field and carefully degauss the enclosure, there is no way to shield the apparatus from the Earth's gravity. It is now well-demonstrated that atomic clocks tick at a faster rate when elevated, just as Einstein predicts in the Theory of General Relativity. Alas, there is no place in the solar system where the gravitational field strength is precisely zero (except perhaps somewhere close to the center of the sun).
I'm curious too. Back when I worked on offshore seismic oil exploration surveys nothing was switched off in the "instrument room". Every time the long hydrophone cable was put back on its reel for whatever reason, some connections within the cable could/would be parted. Then the cable would be reeled back in to so that the fault could be found and repaired. Back and forth; in, out, shake it all about!
BTW, is there access to the 9.1GHz from the caesium tube directly? Should be easier to see sub-ns differences there, with like a 2 channel sampling scope.
If Dr. Barney M. Oliver were still around, he would love to see your workshop. So would I, if I still lived in the Bay Area! Barney would be able to tell you exactly what to do to calibrate the clock, and why -- even if he had nothing to do with the clock product. He had the kind of curious mind that never let anything go by without understanding it, in a way, similar to you, Marc! Barney Oliver was a fascinating man, and a kind mentor to this young engineer, once upon a time, many years ago.
Very interesting, thanks for the nice video. I have a couple of Symmetricom Rb oscillators I play with every now and then. To compare them I built a 10X frequency multiplier do the scope pattern at 100Mhz instead of 10Mhz, of course the noise increases but the error difference is much more pronounced. In the late 60's our USAF lab had a rack mounted instrument called a frequency error expander (could have been from HP) that did the same thing. Not sure how it worked pll, mixers, comb generator etc.
I am a bit confused. I thought that the spin of the excited electron was responsible for the fine split (D1/D2) - if the hyperfine split within D2 is further split by the interactions between electron spin and nuclear spin, what distinguishes the two hyperfine atoms? If they have different spin then they are already separated in the fine stage. Is the difference found in spin *magnitude* on the fine level and then spin *direction* in the hyperfine level?
The fine split is due to the interaction of the electron spin with the electron’s own orbital momentum. so the energy split is dependent on the alignment between the two. BTW in the lower level of the D2 (and D1) line, the one of interest to us, we are in the s subshell so there is no electron orbital momentum and the two spin levels are degenerate in energy. The split only affects the p subshell top levels, which splits in two, and gives the D1 and D2 lines. So at the bottom level, which is common to D1 and D2 lines, we actually do have the two electron spins available. The hyperfine level depends on the alignment of the spin of the nucleus with that of the electron. Two values for that in the s bottom level, if the electron is spin up or spin down. It’s more complicated on the p top level (electron orbital momentum = 1), the total of electron orbital momentum + electron spin + nucleous spin can take four orientations for a single value of the electron spin, so it splits into 4 hyperfine levels, even though this is all for the down spin electron. You need to get into quantum numbers to make sense of that, which is a whole other can of worms, which is why I did not talk about it.
@@CuriousMarc very fair enough! You explained it so well in the video you had me thinking i understood some of it! Thanks for the explanation and for the informative video - please keep making them.
@@lumotroph You did understand it! You bet I asked myself the exact same question. Took me a while to figure that one out. The short version of the long answer is that the top level is split by the spin into fine lines D1 and D2, but it does not split the bottom. Therefore the two spin states are available at the bottom, and split the lines in the two hyperfine levels. If that makes anymore sense ;-)
Watched the first part. Fascinating. Thank you. If I understand correct, one singe period of electromagnetic radiation in caesium-133 proceeds 9192.63177 picoseconds? My imagination tells me that this device inherently measures the difference in the course of processes depending on gravity, magnetic fields, electrical fields, force, motion, temperature etc. Anyway I’m starting to watch the second part.
Wow, one CuriousMarc episode about caesium clock calibration, and now I feel like I understand enough about quantum physics to make sense of quantum computing cubits. If that Zeeman calibration would also apply to cubit sensors, I cannot help but wonder why only three axis are used for quantum compute, wouldn't four axis of spin be measurable? An axis for each surface of a tetrahedron?
Suppose you want to know where you are on the surface of the Earth, but all you can learn is whether you are in the Northern Hemisphere or the Southern Hemisphere. You cannot learn your precise latitude, longitude or altitude. That's the problem with Qubits that are (theoretically) at antipodal locations on the so-called Bloch Sphere. You can learn one bit of information, out of three parameters. You just get the sign bit of one of the parameters and nothing more.
Marc thx for sharing tuning these clocks. From your first video on these clocks you said you had to buy a tube. Can you share how much the tube costs and how many hours are they expected to last. Seems that Microchip bought the company that used to supply these tubes. Seems these can be had from EBAY typically with bad tubes. Thx in advance. Again, thx for sharing.
No these all have old tubes, except the one in the previous video that had its tube swapped in the 1990s. Still old though.. A new tube is $30k, definitely not worth it!
Hm, is that calibration not depending on the earth angegeben field (Intensity and Orientation), or is the shielding effective enough so moving (or flying :) the clock won’t hurt?
There is one thing (well really more than one, but let's stick to this one) that I can't square: While calibrating, you have to use an external generator. I think it's safe to assume, that it doesn't run on atomic precision, so doesn't that effect the the calibration? Or am I missing something and that actually doesn't matter?
Someone may answer this more knowledgeably, but I think it's like this: the calibration freq. in this final step is good to n%, but operating on the 13th decimal place of accuracy, so the effect is of n% to the exp - 13 or so. I think🤔
In a nutshell, the calibration voltages and frequencies don't have to be anywhere near as precise as the output frequency of the cesium clock as they are just used to make the hardware of the clock close enough to the operating points to perform well. The precision of the clock comes from the stability of the atom and electron frequency changes and so as long as the clock is near the operating points of the temperature, magnetic fields, and other parameters, the atomic stability of the transitions can be measured by the unit which is where it gets its reference to generate the precise 10 Mhz output frequency.
It's a primary reference. You don't calibrate to an external generator. You're calibrating to the microwave emission of excited cesium atoms. They are by definition always exactly on frequency.
ב''ה, I'm not in best shape to get all of it, but with all these fine adjustments it amounts to knowing through theory how many emission lines will be where, so then gear that's been calibrated well enough to allow, say, relatively low frequency radio and audio circuits to work confirms you're generating and looking at the right one(s).
A co-worker related an anecdote about when he worked in a standards/calibration center of some kind. First of all, they were so accurate that measurements were noted with the operator in a specific position and even his arms positioned on the armrests exactly! Anyway, some lazy technician didn't want to lug a clock from another room on a different floor, and just ran a co-ax cable from it instead. The difference in altitude showed up easily, as compared with two clocks next to each other. This must have taken place in the 90's, so the equipment would be two decades newer in design. But I think that translates into easier to use, more onboard computer processing rather than raw analog operation; rather than tons more accuracy since this old one is already near the limits of what's possible with that design. So, I think you should be able to show the GR effects by having the two clocks placed a few tens of meters in elevation, with a long cable to connect them both to the 'scope. You just need a multi-story building, not a plane.
If you think of a conventional CRT, the electron beam can be deflected either by an electric field or a magnetic field. If you turn off the internal deflection circuits, the beam will land on some spot close to the center of the screen. If you then rotate the CRT around any of the X, Y, or Z axes, the spot will move as a result of any external EM fields (such as the Earth's magnetic field). In a color TV CRT under normal operation, just turning the CRT monitor on its side will reveal the influence of external fields. That's why CRTs have integral degaussers that typically energize when the unit is initially powered on. Many computer CRTs also included a button on the control panel to manually energize the degausser.
Yes. Goes with the alphabet most of the time but not always. First rev is A, then B, C, D, etc… Sometimes they use T to signify a serious capability upgrade, more than a simple revision, like in the HP 9825T computer, the HP 140T spectrum analyzer, or the HP 180T oscilloscope (successor of the 180C you see in the video).
This really shows the marvel of HP being able to convert physics experiments to a useful product that can be calibrated with standard equipment and by people without a Nobel prize in their pockets.
Your explanation is super clear. You were able to explain enough of the details so us noobs can understand what is going on.
standard equipment ...
I never thought that adjusting a clock could be so interesting!
Hands down the most interesting I've ever en count ered.
Excellent discussion! I was happy to see the 5334B Frequency counter in the video as I was the Service Engineer for that product and designed the self test and service strategy for it.
Awesome! I love that counter, it’s my primary instrument below 1.5 GHz. I have the high stability oven oscillator in it and calibrate it once a year with the Cesium. It stays pretty much on target.
@@CuriousMarc Hopefully the service manual for that counter is dramatically simpler than the 5061. I went to great pains to have the unit troubleshoot itself from known good kernal out to the edge circuits. Most of the testing (assuming the microprocessor is alive and the power supplies work) is just hooking it's outputs up to it's inputs and running it through it's various switching paths. It doesn't require a lot of external test equipment to test and calibrate it. This also greatly simplified the amount of production test equipment needed on the manufacturing line to test it out. I got a nice internal award for that. This was way back in 1980 IIRC so I'm glad you are getting good use out of it.
@@brianbeasley7270 Just out of interest, do you know any of the people that worked on the HP53131/2A? I've always wondered what the story behind the genuinely awful standard oscillator in those counters was - I suspect it has to be accountant related, since I can't see the engineers being exactly happy with shipping a product with a borderline unusable internal timebase.
@@TrimeshSZ Sorry, I didn't know any of them. That was after I left the division. It was most likely a low cost oscillator for the time to lower the price. Sorry it wasn't up to standards!
@@brianbeasley7270 Well, it just meant you had to use an external ref or get the (excellent) high or ultra-high stability options - it was just that a 5 part in 10^-6 oscillator was not what I expected to find in a 10/12 digit/s HP counter!
When I studied engineering the quality of the lecturer absolutely steered my appreciation and interest in a particular subject, you have that gift, I dont know what you do professionally but if you dont lecture or teach its a waste.
My electrical engineering internship was in the Time and Frequency Division at NIST, Phase Noise Measurement group, '93-97, just down the hall from the NIST-7 cesium beam standard. 25 years later, after working in RF communication systems and test equipment, I recently started working at ColdQuanta on quantum computers based on laser cooled neutral Cesium atoms.
Your explanation of Zeeman splitting, and demonstration of the tuning, really helped my understanding of clocks and MOTs. I know many of these concepts as absorbed facts I can regurgitate, without much intuition. It also gave some more insight into the march from parts in 1e14, to 5e-15 of NIST-7, to 1or2e-16 of NIST-F2. And, it's one thing to see an Allen Deviation chart of an atomic clock (or a wandering OCXO tone on a SPA), but watching atomic clock drift on an o-scope made it come alive.
And fun fact, the gravitational redshift at Earth’s surface corresponds to a fractional frequency gradient of -9.8(2.3)×10-20/mm (at that particular lab in Boulder). With Strontium optical lattice clocks at the 1e-21 level, geopotential uncertainty is the dominate error term. It's fascinating to see all the metrology/sensing that atomic clocks play a huge role: magnetic fields, gravity, inertial navigation, Josephson voltage standards, atomic physics, astronomy, electric fields, mass.....
arxiv.org/ftp/arxiv/papers/2109/2109.12238.pdf
18:00 Actually, that was very clear. Best ever. I found myself wishing you had chosen *not* to skip some of the details e.g. how the C-field disallows certain transitions. Very, very satisfying learning. Thanks.
I would be very up for a follow up/bonus video about this too yes.
I had dropped the relativity course in university due to getting lost and it being an optional course of luxury. I appreciate the review and explanation!
Agree. Excellent explanation.
I believe the other transitions destructively interfere under the influence of the C-field’s frequency :)
@@kaitlyn__L Ahh, thank you. Make sense.
I love those clocks! Great video, and I'm really interested to see your time dialation experiment.
Ben, wanna do some Zeeman experiments? I just scored two large mid-century spectrometers. Should be able to resolve the lines (ahem, once restored).
@@CuriousMarc I'm definitely waiting for that!
@@CuriousMarc Mid 17th century? A slightly famous physicist did some ground breaking spectroscopy work that century.
@@johndododoe1411 No, nice instruments from the 1960’s. But good optics don’t get obsolete nearly as fast as electronics. Still very good instruments today.
@1:00 as Alec from Technology Connections would say, "through the magic of buying two of them!"
Waking up and finding 37 minutes of Marc discussing atomic clocks and Zeeman alignment is the best way to start the day.
My exact thought this morning as well.
Well, you just blew the old saying: A guy with one watch can tell you the time. A guy with two watches is never quite sure.. BRAVO !!
At this level even having 3 clocks or (horrors) any odd number of clocks you're still not sure what time it is. You just maybe, statistically, get a better guess.
{^_-}
Atomic physicist here - great explanation overall! Here's some additional information about selection rules:
The 'selection rules' you mentioned are determined by the polarization of the light - the applied magnetic field matters, but only indirectly. If you (arbitrarily) choose any fixed direction in space, you can define your m_F levels to have fixed total angular momentum projection along that direction. If the polarization of the interrogation laser is aligned with this direction, then we call it 'pi-polarized' and it can only drive transitions that do not change m_F. Note that the definition of the m_F levels depends on your choice of quantization axis.
The clock would still work perfectly in exactly zero B. At finite residual B, however, population will begin to be transferred between different m_F levels, unless the B-field is perfectly aligned along your preferred axis. The role of the C-field is to reduce the effect that stray fields have on the angle of the total B-field with respect to this axis. (Simple picture: moving the end of a meterstick by 1 cm changes its orientation much less than moving the end of a 30cm ruler by 1 cm.)
An alternate view (equivalent in any nonzero B field) is to choose the direction of the B-field as your quantization axis. Then it's the impurity of the laser polarization projection (along the B-field axis) that causes the unwanted transitions to occur. This has the advantage of ensuring that the corresponding m_F levels are so-called 'energy eigenstates' of the full Hamiltonian, including the Zeeman interaction - but at the expense of more complex selection rules.
But either way you do the computation, you get the same result - the component of the B field perpendicular to the light polarization must be zero, or you will get unwanted frequency components.
Here I am learning about NMR spectroscopy in ochem 2, deciding to take a break with an exciting new CuriousMarc video, and getting most of the lecture theory explained back to me (plus a lot more.) No complaints though. Fascinating video. Thank you all for what you do and for taking the time to document it
Back in the early 60's NMR was the latest thing never realized how that experimental lab instrument would change chemistry. I had a medical MRI a few years back and got curious how they worked, most fascinating.
It's amazing how many 'explanations' for the clock are 'it measures hyperfine transitions of cesium.' And are as long if not longer than this video. It's like telling you how a car works: 'it makes gasoline explode.' Excellent work. You've done a great job especially on elements that are hard to grasp in text. I don't think people really appreciate the scale of these measurements. The leap from theory to a practical machine is almost unreal.
I opened this channel and looked at the picture. OMG this guy found a pair of HP Cesium clocks. When I was working with HP, I sold two of them. Both went to Lockheed. After delivery I never saw them again. In those days they were accurate to within one second in 200,000 years. Better accuracy now.
The only thing better than this episode is the fact that I understood exactly what you were doing and explaining! I wish I had some of that test gear, and one of those beautiful clocks!
Thank you Marc and Team for another amazing experience! I can't wait for the time dilation clock check!
What a fantastic explanation, you make a wonderful teacher Marc, Thank you.
That was an excellent and very good explanation of the C-field and why it is required. Thank you for another outstanding video.
I've never understood why this channel sits under 150k subscribers, it's content and quality is outstanding every time.
It is because you have to be of a certain level to understand what's going on. The chin droolers that make up 90% of youtube can't keep up.
@@stargazer7644 Yes, and I still find it interesting in spite of drooling. Wish others could dream as I do, but you know....
The HP 5518A heterodyne laser Interferometer also uses Zeeman effect to split HeNe laser light into 2 opposite polarized beams, with a few MHz difference in frequency, so that the receiver can tell, if the measurement mirror is moving towards or away from receiver.
Another instrument with lots of HP magic inside, can measure absolute distances in nm range or flatness of surface plate very accurately.
Wow, I definitely have to look that one up!
HP engineering sure was great.
magic is the proper word...or perhaps reverse alien enginering....
that's also how they found the incredible G wave. LOL talking about a 10 to the -21 signal. They found something but I don't think it has anything to do with quadrupole gravity waves
I, for one, get excited when the elevator music starts. Great stuff! I look forward to seeing how you use your clocks.
Here I am on the last steps of restoring and adjusting a french turn of the century mantel clock to + - 10 minutes PER DAY and super happy with that, and these guys adjusting to the billionth decimal a cesium clock.
Turn of 19th century I take it!
I should adjust my best crystal clock, in a HP 5360A frequency counter. The manual suggests adjusting it against WWV. Only about 5 powers of ten worse then this cesium clock.
I remember when I was a kid in 70s, I saw a TV science program which was about relativity, time and speed of light. They used two atomic clocks like those here. They put one in a NASA airplane and another one on the ground. After the airplane did a couple spins the atomic clocks showed some difference about a few nanoseconds. Then the funny guy placed his twin brother in an spaceship which traveled at the speed of light. After a couple minutes, he came back to Earth and he found his brother pretty old. They said the story wasn't a science fiction at all and it was very amazing for me. Perhaps the best science program I ever saw on TV in those years.
I knew several of the words used in this video.
Every time a video is posted, I am amazed at what is presented. I would have bet money that 2 HP atomic clocks were not operable at this late date. Those tubes are not replaceable anymore.
I wonder if a vector voltmeter such as the HP 8508A or 8405A might not be a better instrument for detecting minute phase drifts between clock signals. They offer phase resolution down to 0.1deg, which would be difficult to resolve with the oscilloscope. They might also be less susceptible to drift or jitter in the triggering point as compared to an oscilloscope.
I learned quite a lot. One of the most entertaining classes I ever attended.
What a fantastic video, Marc and the guys on top form. I love the amount of work that went into explaining the somewhat complicated (understatement of the year) quantum physics - Marc, you're a hero.
I’ll stay tuned (hope I don’t drift too much!) 👍
That's a very nice demonstration and explanation of the Zeeman effect and the magnetic alignment of the HP5061. I've never seen that before in such a detail. Anyhow, I suggest to do frequency comparisons (Cs vs Cs or vs GPS) by time-nuts methods. That is a phase comparison method by means of a high resolution T.I. counter, like your HP5334A. By using John Miles free TimeLab program, which might directly support your counter over GPIB, you can make comfortable stability (Allan Deviation) and uncertainty measurements down into the 10^-13 region, over many hours. That is required to overcome short / medium termed jitter especially of the GPS reference. Easy to accomplish, and maybe making a nice next video.
Should you ever wonder again whether to include 18 minutes of theory, by all means, do include it. This was one of your best episodes ever.
I can't wait to see what experiments you're able to perform with two highly calibrated cesium clocks.
The main thing to demonstrate is that timekeeping is affected by gravity. If one of the clocks is elevated above the other by a few meters, it should be able to observe that it gradually gains time on the one positioned below it. Even with just one working cesium clock, the GPS reference time can play the role of the baseline clock.
Now they just need couple of business jets to fly around the world.
Or just mountain top to Death Valley gravity field.
@ Scott Manley is currently getting his pilot license. And he is living in the area.
Keeping one clock at sea level, and the other up a mountain, should produce a measurable difference.
Of course, that means finding a way to make one of the clocks portable, but I think HP was thinking of that when they built these things.
Thanks!
Fascinating. I wish you’d been a lecturer whilst I was at university. You’re a natural! Very clear, and your enthusiasm for the topic is infectious.
This is a wonderful example of engineering as the application of science to a problem. Kudos to the HP engineers.
I wish you had been my quantum mechanics teacher during my physics degree. You’re speaking directly to me when you express the theory intertwined with the experimentation and engineering utilization of the phenomenon. What an 18min!
Awesome explanation! I feel smarter for watching, and that often happens when I watch your vids
On the day of the transition from DST to normal time. What perfect timing! 😁
I hate to tell you, but you're a week early.
me: forgets about daylight savings time and doesn't even notice for a day or two
marc: my cesium clock is 0.0000000001Hz out of spec and we need to calibrate it.
Thank you for that reminder. I thought I was just having strange experiences in the kitchen over the weekend.. but my clock in there needed changing
Very cool!!! Avoid brain twisting explanation you ask, NEVER! Thank you so much for sharing all this with us! I grew up around engineers, listening to your explanations give me a warm feeling of being home again. Fascinating stuff. By far my favorite episode on this channel. What could be more mysterious then time? Liquid gold!
As a stained glass artist I highly approve of that window!!
Brilliant explanation as ever. Took me right back to Electronic Theory of Matter lectures 48 years ago.
Great explanation. I was actually able to follow you, and I'm not the brightest bulb in the electromagnetic spectrum.
These videos are pretty awesome. Love the theoretical description next to the hands on demonstration.
This atomic clock is a genuine condensate of Nobel prizes.
This video series really helps me appreciate 100 years of progress in the science of quantum physics.
As a career EE it is also fascinating to learn how a thorough understanding of quantum physics led to the creation of a very precise frequency reference which could be manufactured in the 1960/1970’s era and (with calibration) still meet its specs many years later.
I own a few vintage HP instruments myself but nothing in the “atomic clock” category.
My collection includes a 412A DC VTVM and a 3456A 6.5 digit DVM which both function very well. I frequently use them. Neither required extensive restoration. I found my 412A many years ago in a junkyard/recycling center with its mains power cord and probe leads cut off. It was free for the taking. I picked it up mainly because it looked cool in a very retro way. I never expected it to be functional. But out of curiosity 2 years ago I decided to see if I could get it to work. I was rather surprised to find no faults or issues beyond needing to replace the missing cables and probes. All of its capacitors and vacuum tubes tested good. The optical chopper still worked. I love it’s 100 meg input resistance for DC voltage measurement. It also works very well for Ohms measurement. The 3456A was an eBay find which needed only the replacement of some electrolytic capacitors in its power supply. I also have an 8660C frequency generator which partially works but needs to have the bandpass filters in the 0-100 MHz plug-in rebuilt.
Keep up the great videos please!
I don't understand anything you guys are talking about but love being subscribed watching your passion.
I watched this video shortly after waking up and I still managed to follow your explanation of the hyperfine energy levels and Zeeman lines. Excellent job at communicating it clearly! You've now inspired me to dig into the literature on magnetic quantum numbers and selection rules, since that's a level of detail that I've only ever heard of in passing before. It's good to have a practical application to tie the knowledge back to.
I didn't understand a thing, and I still enjoyed it ;)
Marc, you guys should really get in touch with Tom Van Baak for your journey with cesium clocks and precision time keeping. His collection is probably second only to NIST itself.
I wonder if Segal's Law ( "a man with a watch knows the time. A man with two does not" ) still applies when both the timepieces are Atomic?
Ha, that is why I got my second Rb oscillator. I could see a difference between my first Rb and the GPS disciplined oscillator but I didn't know which. With two Rb oscillators I could see the GPS was the issue. It needed a better antenna, small dropout on the GPS would slightly skew the PLL slightly.
Only until your accuracy reaches 5.39×10−44 s. 😜👍🏻
"... A man with two and an HP oscilloscope does not".
I think I understood more about this topic than the rest of my education in this one video. Very well done on the explanation and the restoration
This video gave me a series of those headaches with pictures. You know, “an education!” That was awesome to see!
I could listen to you lecture about this kind of stuff all day!
Fascinating material and well explained.
HP machine designers were in a class of their own. And most still operate as designed.
I have several test machines from the 70’s and 80’s that still work as intended.
Please make a detailed no hold back video about this. This is just so captivating.
It's CuriousMarc lecturing on physical chemistry and quantum physics, and it's so cool!
You laid out the spectral lines better than any professor at my university when I studied chemistry. Makes me wish I watched this video in 2007 or so.
Zeeman's lab gear and experiments (and that stained glass too)? Definitely great and brilliant in its simplicity! Coming up with it was the hard part, doing actual experiments is straightforward, with no multi-million-yankee-bucks worth of equipment. Makes me wonder if there's still some science to be done that doesn't require very advanced and expensive technology.
That HP scope is nice, but fades in comparison with Usagi's HP 150A :)
So, any video on NMR, EPR or (unrelated, but close) mass spectrometry? That would be great. I was taught the theory of operation and how to interpret the spectra (and determine the structures), but never worked on a NMR or mass spectrometer myself.
Nice watch too.
Wow! This was just fantastic, I finally feel like I understand what the SI unit for 1 second actually means. A concrete example with HP cukcoo clocks and everything :D
excellent video MARC and TEAM!
When comparing the beam current after C-field adjustment hasn't the "beam I-meter" pot been adjusted to keep the maximum on scale when adjusting the amplitude of the audio oscillator, so couldn't that explain the beam current reduction post-adjustment? Not having a 5061 to hand I seem to remember that one just adjusts this so the beam current reads 20 in operation.
best physic video of my life u are great as hp designer of those clocks
Fantastic. I was thinking about an experiment which would be possible in the basement without too much expense. How about verifying the speed of light in different mediums?
Patience:) Good alignment and calibration!
I can't wait for the seemingly inevitable episode about the Ramsey effect!
I knew a lot of this from studying physics, but I still watched all of it because I found the explanation from an instrument/technician’s perspective to be an interesting change from the atom’s-perspective way I was taught it. All the same components of course, just a different reference frame.
This video gave me enough confidence to finally try adjusting the kitchen scale clock back to "normal" aka winter time
Thank you , this was excellent theoretics and lab work.
I certainly didn't skip ahead ! I find it fascinating ! Getting some sort of glimpse of what is the fine structure (difference of energy levels dependin on spin) and the hyperfine structure (when applied inside a magnetic field) - and how this applies to define a constant for time (or rather the measurement of time within a reference frame) - and then how it this all applies to the real world.. and so how it really works and how it is calibrated and how it can be done.. (I didn"t understand 10% of it, but it's fascinating nonetheless)
Fascinating stuff! ^^) That is mind-blowing, having such equipment at hand in your basement!
Fantastically clear explanation of both the underlying physics and the calibration process. I feel like I actually understand how cesium clocks work now!It’s beautiful the way you can use very pedestrian lab equipment to calibrate an instrument to deliver time accuracy on the order of 10^-13. What an absolutely brilliant device!
Next up: Cesium fountain clock? 😉
BTW: What’s the lifetime of the cesium tube? Does the cesium somehow recirculate, or does it eventually get used up and the tube needs to be replaced?
As I'm watching this I realise that the c field is like the heater in a oven crystal clock, kinda,
The magnetic shielding is like the insulation on a oven crystal clock as well,
Block out/insulate as much as possible, and then provide your own standard/reference above what still leaks in (out in the case of oven clocks but still, I think this analogy is almost perfect)
Absolutely amazing video as always Marc! You are so lucky to have access to not one but two of those clocks!
I managed to get hold of an old rubidium reference module from an aircraft but haven't done anything with it to make it into a useful reference yet. Even when I do it'll be way less accurate than those big boys hehe
Not by much, just set it up as a PLL with a GPS as the long term reference and Bob's your uncle
@@craigs5212 I shall look into that 😁 at present I bypassed the fried power supply and verified the internal stuff was still working, but then put it on the shelf with various other projects I've not finished yet 🤣
I hope the 'maybe' at the end was not a threat ;-). Thank you Professor Marc for this wonderful Monday morning lecture. Although all of the quantum stuff goes way above my hat I could grasp the overal gist of your explanation. I also never could have surmised two of my fellow countrymen (whose names I once found in a Dutch science museum) would be mentioned in your famous lecture. Wonderful video and looking forward to your 'dual Cesium clock experiment' :o)
It would be super cool to see you repeat the Hafele and Keating time dilation experiment. Also expensive I would imagine! You need a pretty long flight to get results in the nanoseconds.
It would be fascinating to try to predict the results of the experiment beforehand and see how it plays out in reality.
When Marc starts the elevator music, time to grab the popcorn and pay attention! IMHO, the best part of the videos. Now to see what @MarcoReps has cooked up.
23bit Encoder 😮
Marco Reps rocks!
Now you have 2 clocks you are uncertain again. You now need to get another 3, so you have a cluster of 5, so that you can use the average to get the error from the outliers, and use that average to both get the right time, and also verify all 5 are operating correctly.
While they are able to block the earth's magnetic field and carefully degauss the enclosure, there is no way to shield the apparatus from the Earth's gravity. It is now well-demonstrated that atomic clocks tick at a faster rate when elevated, just as Einstein predicts in the Theory of General Relativity. Alas, there is no place in the solar system where the gravitational field strength is precisely zero (except perhaps somewhere close to the center of the sun).
Ebay?
Love the video. I'm curious do you have to "calibrate" the clock every time you power them up ?
I'm curious too. Back when I worked on offshore seismic oil exploration surveys nothing was switched off in the "instrument room". Every time the long hydrophone cable was put back on its reel for whatever reason, some connections within the cable could/would be parted. Then the cable would be reeled back in to so that the fault could be found and repaired. Back and forth; in, out, shake it all about!
after watching this tutorial I think I might be ready to set the clock on my VCR
BTW, is there access to the 9.1GHz from the caesium tube directly?
Should be easier to see sub-ns differences there, with like a 2 channel sampling scope.
maybe you will see the 9.1 GHZ....but not down to the 9.1 xx xxx xxx Hz
That was very well explained, I was actually able to follow it !
Just the kind of video I need at 7am after I’ve just woken up
Wake up juice!
@Jaut-76 Lol, me too, and even before the morning coffee!
I wonder what the current equivalent is and how it is calibrated.
If Dr. Barney M. Oliver were still around, he would love to see your workshop. So would I, if I still lived in the Bay Area!
Barney would be able to tell you exactly what to do to calibrate the clock, and why -- even if he had nothing to do with the clock product. He had the kind of curious mind that never let anything go by without understanding it, in a way, similar to you, Marc! Barney Oliver was a fascinating man, and a kind mentor to this young engineer, once upon a time, many years ago.
Barney Oliver was an amazing genius!
Very interesting, thanks for the nice video. I have a couple of Symmetricom Rb oscillators I play with every now and then. To compare them I built a 10X frequency multiplier do the scope pattern at 100Mhz instead of 10Mhz, of course the noise increases but the error difference is much more pronounced. In the late 60's our USAF lab had a rack mounted instrument called a frequency error expander (could have been from HP) that did the same thing. Not sure how it worked pll, mixers, comb generator etc.
Wow, my grandfather co-invented the color spectrophotometer in the 1920s at MIT - I had no idea it was used to tell time too!
Excellent experiment.
I am a bit confused. I thought that the spin of the excited electron was responsible for the fine split (D1/D2) - if the hyperfine split within D2 is further split by the interactions between electron spin and nuclear spin, what distinguishes the two hyperfine atoms? If they have different spin then they are already separated in the fine stage. Is the difference found in spin *magnitude* on the fine level and then spin *direction* in the hyperfine level?
Also: this was just such a brilliant video and explanation - thank you!
The fine split is due to the interaction of the electron spin with the electron’s own orbital momentum. so the energy split is dependent on the alignment between the two. BTW in the lower level of the D2 (and D1) line, the one of interest to us, we are in the s subshell so there is no electron orbital momentum and the two spin levels are degenerate in energy. The split only affects the p subshell top levels, which splits in two, and gives the D1 and D2 lines. So at the bottom level, which is common to D1 and D2 lines, we actually do have the two electron spins available. The hyperfine level depends on the alignment of the spin of the nucleus with that of the electron. Two values for that in the s bottom level, if the electron is spin up or spin down. It’s more complicated on the p top level (electron orbital momentum = 1), the total of electron orbital momentum + electron spin + nucleous spin can take four orientations for a single value of the electron spin, so it splits into 4 hyperfine levels, even though this is all for the down spin electron. You need to get into quantum numbers to make sense of that, which is a whole other can of worms, which is why I did not talk about it.
@@CuriousMarc very fair enough! You explained it so well in the video you had me thinking i understood some of it! Thanks for the explanation and for the informative video - please keep making them.
@@lumotroph You did understand it! You bet I asked myself the exact same question. Took me a while to figure that one out. The short version of the long answer is that the top level is split by the spin into fine lines D1 and D2, but it does not split the bottom. Therefore the two spin states are available at the bottom, and split the lines in the two hyperfine levels. If that makes anymore sense ;-)
Remember to redo the procedure every time something changes in or around the lab. Like a truck parking in the driveway. 🙂
Ow wow, the original notes from professor Zeeman. Zeeman means Sailor by the way :) I'm Dutch, I can read those notes!
Nice, I got it, well bits of it but more than when I started !...cheers.
That is going to need one hell of a watch strap 🤖
Fantastic, awesome episode guys. I vote for more tests. 😊
Watched the first part. Fascinating. Thank you. If I understand correct, one singe period of electromagnetic radiation in caesium-133 proceeds 9192.63177 picoseconds? My imagination tells me that this device inherently measures the difference in the course of processes depending on gravity, magnetic fields, electrical fields, force, motion, temperature etc. Anyway I’m starting to watch the second part.
Wow, one CuriousMarc episode about caesium clock calibration, and now I feel like I understand enough about quantum physics to make sense of quantum computing cubits. If that Zeeman calibration would also apply to cubit sensors, I cannot help but wonder why only three axis are used for quantum compute, wouldn't four axis of spin be measurable? An axis for each surface of a tetrahedron?
Suppose you want to know where you are on the surface of the Earth, but all you can learn is whether you are in the Northern Hemisphere or the Southern Hemisphere. You cannot learn your precise latitude, longitude or altitude. That's the problem with Qubits that are (theoretically) at antipodal locations on the so-called Bloch Sphere. You can learn one bit of information, out of three parameters. You just get the sign bit of one of the parameters and nothing more.
Amazing Sir! Thank You!
Marc thx for sharing tuning these clocks. From your first video on these clocks you said you had to buy a tube. Can you share how much the tube costs and how many hours are they expected to last. Seems that Microchip bought the company that used to supply these tubes.
Seems these can be had from EBAY typically with bad tubes.
Thx in advance.
Again, thx for sharing.
No these all have old tubes, except the one in the previous video that had its tube swapped in the 1990s. Still old though.. A new tube is $30k, definitely not worth it!
Hm, is that calibration not depending on the earth angegeben field (Intensity and Orientation), or is the shielding effective enough so moving (or flying :) the clock won’t hurt?
It is. If you change the orientation you’re supposed to repeat the procedure. Also avoid change in surroundings.
There is one thing (well really more than one, but let's stick to this one) that I can't square:
While calibrating, you have to use an external generator. I think it's safe to assume, that it doesn't run on atomic precision, so doesn't that effect the the calibration? Or am I missing something and that actually doesn't matter?
Someone may answer this more knowledgeably, but I think it's like this: the calibration freq. in this final step is good to n%, but operating on the 13th decimal place of accuracy, so the effect is of n% to the exp - 13 or so. I think🤔
In a nutshell, the calibration voltages and frequencies don't have to be anywhere near as precise as the output frequency of the cesium clock as they are just used to make the hardware of the clock close enough to the operating points to perform well. The precision of the clock comes from the stability of the atom and electron frequency changes and so as long as the clock is near the operating points of the temperature, magnetic fields, and other parameters, the atomic stability of the transitions can be measured by the unit which is where it gets its reference to generate the precise 10 Mhz output frequency.
It's a primary reference. You don't calibrate to an external generator. You're calibrating to the microwave emission of excited cesium atoms. They are by definition always exactly on frequency.
ב''ה, I'm not in best shape to get all of it, but with all these fine adjustments it amounts to knowing through theory how many emission lines will be where, so then gear that's been calibrated well enough to allow, say, relatively low frequency radio and audio circuits to work confirms you're generating and looking at the right one(s).
When quoting timing accuracy times as 1e-10 for example, what exactly does this mean? 1e-10 seconds of drift in X amount of time?
Yes there is always a time period associated with that. Per year, per month, etc…
A co-worker related an anecdote about when he worked in a standards/calibration center of some kind. First of all, they were so accurate that measurements were noted with the operator in a specific position and even his arms positioned on the armrests exactly!
Anyway, some lazy technician didn't want to lug a clock from another room on a different floor, and just ran a co-ax cable from it instead. The difference in altitude showed up easily, as compared with two clocks next to each other.
This must have taken place in the 90's, so the equipment would be two decades newer in design. But I think that translates into easier to use, more onboard computer processing rather than raw analog operation; rather than tons more accuracy since this old one is already near the limits of what's possible with that design.
So, I think you should be able to show the GR effects by having the two clocks placed a few tens of meters in elevation, with a long cable to connect them both to the 'scope. You just need a multi-story building, not a plane.
How is the "zero field standard" implemented then? 15:37
If you think of a conventional CRT, the electron beam can be deflected either by an electric field or a magnetic field. If you turn off the internal deflection circuits, the beam will land on some spot close to the center of the screen. If you then rotate the CRT around any of the X, Y, or Z axes, the spot will move as a result of any external EM fields (such as the Earth's magnetic field). In a color TV CRT under normal operation, just turning the CRT monitor on its side will reveal the influence of external fields. That's why CRTs have integral degaussers that typically energize when the unit is initially powered on. Many computer CRTs also included a button on the control panel to manually energize the degausser.
@@BarryKort I think you misunderstood my question. At 15:37, the author mentions a "zero field standard". My question pertains to this..
I wonder if 74 Gear and/or Mentour Pilot might be able to assist with a future episode.
All I can tell from this video. Is that Hollywood really nailed the characterisation of a 21st century scientist.
Is the A in HP part numbers a revision?
Yes. Goes with the alphabet most of the time but not always. First rev is A, then B, C, D, etc… Sometimes they use T to signify a serious capability upgrade, more than a simple revision, like in the HP 9825T computer, the HP 140T spectrum analyzer, or the HP 180T oscilloscope (successor of the 180C you see in the video).