[time-nuts] 8th Symposium on Frequency Standards and Metrology

Magnus Danielson magnus at rubidium.dyndns.org
Mon Oct 19 00:19:43 UTC 2015


Hi,

Yes, it was, so I wanted to convey it.

PTB trendline from 1E-19 downto 1E-21 as memory recalls it. Messed that 
up and I don't remember the details properly. Damn stable anyways.

Also forgot to mention that Prof. Enrico Rubiola was there too, and we 
had lots of fun discussions through the week.

Cheers,
Magnus

On 10/19/2015 01:04 AM, Bob Camp wrote:
> Hi
>
> Very interesting
>
> Thanks!!
>
> Bob
>
>> On Oct 18, 2015, at 5:50 PM, Magnus Danielson <magnus at rubidium.se> wrote:
>>
>> Hi,
>>
>> I thought a small report might be appreciated.
>>
>> It's been a very intensive week. Fellow time-nuts Attila Kinali and Marek Peca attended. Attila and I hanged out with Florian Teply on Friday after the sessions.
>>
>> Anyway, in a sense of impeccable humor, the host of the conferance, Fritz Riehle of PTB, had mounted a Black Forrest Coo-Coo clock on the wall of the seminar room. This interrupted the nice overlook that David Wineland (who got his Nobel price 2012) with amusement as result. I ended up using the Coo-Coo clock as alternative time reference during the seminar.
>>
>> Among the interesting things said was that a group have now been formed to look at the redefinition of the SI second in terms of the optical clocks. The motivation is that since the last symposium, the optical clocks have now with margin surpassed the microwave clocks. By the look at the trend-curves, by the next symposium the distance should be significant. Regardless, if a redefinition is to be done, there is a lot of homework to be done before it can be settled and then we should expect performance to have improved significantly.
>>
>> Looking at the presentations, several contenders was presented, and it is a wide range of approaches being done. Interesting is also how comparison between both different implementation of a particular transition but also between different transitions is done. Optical combs has become a valuable tool in wide use and optical resonators of various forms is used in combination to the various form of traps.
>> We see Sr, Yb, Al, Mg and Ca clocks being attempted and compared.
>>
>> Numerous approaches to compare on distance was also presented, where PTB is mighty proud of their new link which has a trend-line for 1E-19 downto 1E-19 in the modified Allan deviation plot. I naturally spotted some systematics there, but they have good margin for the current clocks, so it is impressive as it is. They have changed the laser amplification method from EDFA to fiber-based, and their pump-lasers is being locked too. The amplifier is a bit narrow-band, but does not look to dominate the properties, so they are fine for now.
>>
>> PTB and SYRTE have now a link between them to allow for comparison of their clocks, and the NPL - SYRTE link will soon be completed. More links in France is on-going as well as the link to INRIM. The SP - MIKES link was listed also.
>>
>> Several improvements in satellite two-way methods was also shown, and people have already done test to compare optical clocks over existing methods (which is limited by todays standard) but the new links coming looks really promising for international comparison.
>>
>> It was also interesting to see the presentation on cryogenic sapphire whispering gallery oscillators.
>>
>> One interesting project is what they call "NIST on a chip" which attempts to provide not only frequency but several other units in form of a chip-scale device. So, they are looking wider on how frequency can be used in small form-factor, which will be of interest for length, current, voltage etc.
>>
>> Several groups have been looking at modified Ramsey interrogation by applying a modified pulse-mechanism that helps to reduce the first degree light shift. This new scheme is called hyper Ramsey interrogation scheme. Another interesting technique being discussed was the spin-squeezing, which promised an improvement in 20 dB.
>>
>> Several presentations where on the topic of optical line measuring which may not be of interest for clock transitions, but oh did the methods being used share similarities!
>>
>> One presentation was on the use of GPS satellites on detecting Dark Matter. That guy ended up sharing lunch with us, and I think Marek and me answered some of the questions he had about satellites and their signals that he needed for his research. That we just "happen" to know this, is another thing. :)
>>
>> The breakfast, coffee breaks, lunches, poster sessions and dinners as well as late night sessions all had lovely discussions. Phase noise, cross-correlation issues and delta-counters effect on ADEV was among the issues that came up regularly. Great fun with old and new friends.
>>
>> I concluded that I have at least 3 papers to write as a consequence of this trip.
>>
>> NIST presented the work on chip scale clocks they are working on, and one of their uses is in magnetic sensors. This had led them to test it in PTBs lab for biosignals. PTB has built a room which is very very quiet in terms of magnetic fields, so quiet in fact that it is the magnetically quietest place in the solar system. Attila and me naturally took the opportunity to visit this lab, as it was located relatively central in Berlin. The building starts of with an EMC shield, and then have large coils that not only cancels the earths magnetic field, but also the fluctuations. Then they had built a room which has 7 layers of mu-metal, really built as a box-in-a-box-in-a... and the door is an interesting object in itself, as it slide sideways and connect all 7 layers at the same time. It took them 4 years to master the demagnetization of the mu-metal, and it has been operational for 10 years now. Proud by friendly techs showed us what it can do and how it reacts. Very cool indeed. Th
 e

>   y should be proud, it's an achievement. I made the comparison to the things we do in atomic clocks.
>> They now have funding for an 8th layer of mu-metal to make the field even more homogenic. Oh, the lights in there where optical bent pipes. :)
>>
>> In all, quite an experience.
>>
>> So, the field is moving, things are happening, it is quite interesting future.
>>
>> When I woke up at the hotel Saturday, all but one was gone. Strange feeling, but I then got to meet a friend who now lives in Berlin, and that warmed me up again. :)
>>
>> Cheers,
>> Magnus
>>
>> On 10/09/2015 08:54 PM, Magnus Danielson wrote:
>>> Fellow time-nuts,
>>>
>>> Next week is filled with interesting stuff as we gather in Potsdam for
>>> this:
>>>
>>> https://www.ptb.de/8fsm2015/about-the-symposium/
>>>
>>> I and Attila will be there, so who will join us?
>>>
>>> PS. For the moment I actually don't know how many Cs-clocks I have...
>>> it's complicated.
>>>
>>> Cheers,
>>> Magnus
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