88Sr+ ion-clock live stream
Tom,
On 2019-12-09 02:30, Tom Van Baak wrote:
Magnus,
The mf values of +3, +2, +1, -1, -2, -3 transitions have a relatively
strong sensitivity to magnetic field, with a strong linear term on the
magnetic field strength, where as the 0 transition has a much weaker
quadratic sensitivity, assuming weak magnetic field which is fair
assumption.
You can see this dramatically by turning the cfield adjustment from
min to max:
A good illustration of it, it does not show the fine-grained movement of
the 0 transition, because of the scale, but it is there.
This is true for any atomic transition, so it is not unique
to Cesium. Cesium has however the second weakest (of classical neutral
atom microwave frequency, only Thallium being better) magnetic
sensitivity for it's hyper-fine transition.
Some late night reading about Thallium:
1957, Kusch
"Precision Atomic Beam Techniques"
https://ieeexplore.ieee.org/document/1536252
kusch1957.pdf
1960, Mockler, Beehler, Snider
"Atomic Beam Frequency Standards"
http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.846.7115&rep=rep1&type=pdf
1963, Beehler, Glaze
"Experimental Evaluation of a Thallium Beam Frequency Standard"
https://tf.nist.gov/general/pdf/211.pdf
1966, Beehler, Glaze
"Evaluation of a Thallium Atomic Beam Frequency Standard at the
National Bureau of Standards"
https://tf.nist.gov/general/pdf/9.pdf
1983, Ramsey
"History of Atomic Clocks"
https://tf.nist.gov/general/pdf/1916.pdf
https://nvlpubs.nist.gov/nistpubs/jres/088/jresv88n5p301_A1b.pdf
Thanks for those links, I have read some of these, as one might have
guessed. With todays technology, we would have been more inclined to
Thallium of the two, as the two technological drawbacks of Thallium at
the time, the higher
Even with cesium, you can
tweak the frequency of transition with the change of the magnetic field
(B-field in the lingo). All such cesium clocks is really secondary
standards, even if marketing have been boasting their contribution a
lot.
Not sure what make/model cesium clock you're talking about here. Just
because there are knobs to tweak doesn't demote them to secondary.
Just because you use the right atom and isotope does not give you a
primary standard. The clock build of analog cesiums (HP 5060A, 5061A/B
and 5062A to name a few) does not on their own balance their synthesis
chain to the shift that their open-loop magnetic field causes on the
cesium transition. This is comparable to the shift of the wall being
balanced by the buffert gases in a gas-cell such as rubidium (but lately
also cesium). Only the large laboratory cesium clocks was able to
self-calibrate the shift caused by magnetic field. Modern standards such
as FTS 4040, FTS 4065 and HP 5071A is able to servo the magnetic field
to balance it. The improved stability and accuracy is significant, but
for TAI purposes, that is not sufficient either, they are only used for
stability but not accurate observation of the SI transition.
So, we have some pretty darn cool toys, but primary references, well not
so much IMHO.
Cheers,
Magnus
Today (a mere 4-and-a-half months since my post below) we managed to lock
the ultra-stable laser to 3 pairs of Zeeman-components of the ion.
As previously, this is a complex experiment so it may fail at any time,
enjoy it while it lasts: https://www.youtube.com/watch?v=hZQtlHXECQ4
The servo that steers the clock-laser onto the clock-transition of the ion
measures quantum jumps on the red and blue side of each Zeeman-peak, and
strives for the same amount of jumps on both sides.
The overlay image cycles between a few different images:
- The clock-transition line-center estimates, based on the mid-point
between a Zeeman pair. Unfortunately this is still in units of the final
double-pass AOM that shifts the clock-laser frequency before the ion. I'll
try to improve this so it relates to the actual optical frequency at 445
THz in the future. - an estimate of the magnetic field (1.2 uT or so), again three separate
estimates based on the Zeeman-pairs. - The 'quantum-jumps' observed on the red and blue side of each transition.
The servo strives for equal amount of jumps on the blue and red side - then
we know we are centered on the peak. You can note how noisy the data is
(with Poisson statistics) when we only have one atom to work with! (Compare
to a Ceasium clock with a SNR of 1e6 (or so I hear))
We roughly checked the observed line-center against the drift-model for one
of our active Hydrogen-masers and so far they agree to about 3e-15. The
BIPM SRS recommended frequency is given with an (conservative?) uncertainty
of 1.5e-15 [1]
regards,
Anders
[1] https://www.bipm.org/utils/common/pdf/mep/88Sr+_445THz_2017.pdf
On Fri, Dec 6, 2019 at 5:39 PM Anders Wallin anders.e.e.wallin@gmail.com
wrote:
Hi all, you may find our live-stream from the lab amusing:
https://www.youtube.com/watch?v=z9VFbs4FogY
The central bright dot is fluorescence at 422nm from laser cooling a
single trapped 88Sr+ ion. The ion emits about 1e7 photons/s at most and we
currently detect about 500 of those in a 20ms detection window (using a
Hamamatsu PMT module).
The bar-chart shows the clock-transition spectrum at 445 THz (674nm). The
X-axis is a drive-frequency to the last AOM that shifts the clock-laser
frequency to coincide with the ion frequency. The frequency around 75.9MHz
should be doubled to get the real optical frequency-shift (double-pass AOM).
We 'shoot' 100 pulses at each clock-laser frequency towards the ion, and
detect how many times we are able to drive the ion into the 'dark'
clock-state. The clock state is long-lived (400ms or so), and detection is
by turning on the cooling and noticing that the ion is dark. In theory the
ion should blink in the camera-view also, but the exposure-time is now long
enough that there is not much visible blinking.
The height of the bars show that we are able to excite the
clock-transition with about 20-30% probability at the moment.
The clock-transition splits into five symmetric Zeeman pairs, four of
which are observed in this scan range. We have two magnetic shields and
compensating electromagnets to reduce the DC magnetic field to 0.4 uT or
so. This splits the outermost components by about 20kHz (10kHz AOM-range in
the figure, doubled). The line-center is around 75.945 MHz on the AOM. This
corresponds to the clock-transition center, 444 779 044 095 486.5 Hz. Maybe
we should make this more obvious, an AOM number like 75 MHz is not so
impressive...
The peaks are now around 500Hz wide. This is about 1e-12 fractional. There
is room for improvement as the 88Sr+ clock-state natural lifetime of 400ms
only limits linewidth to 4Hz or so... Line-center (the middle of all zeeman
peaks) can be determined more precisely than linewidth.
The control system (ARTIQ) is now just repeating the same scan over and
over, takes around 1h per scan (12kHz range with 25Hz resolution IIRC), and
each new spectrum is plotted with a new color.
Enjoy it while it lasts - this is a live stream and anything may happen
(cooling laser unlocks from Rb-cell, clock-laser unlocks from ULE-cavity,
ion disappears, whatever....). Ion storage times have been in the ~4 days
range previously - so I am hoping it will run nice now for 24h or so.
Final clock-operation will not scan this thoroughly over all the peaks,
just three of them, and just one frequency on the left/right side of each
peak - and then a numerical servo locks on to the center of each peak.
If you run an optical clock I hereby challenge you to live-stream it and
post here!
cheerio,
Anders
Hi
Very cool !!!
Sort of sounds like we will not be doing this in a basement lab any time soon :(
Bob
On Apr 23, 2020, at 11:27 AM, Anders Wallin anders.e.e.wallin@gmail.com wrote:
Today (a mere 4-and-a-half months since my post below) we managed to lock
the ultra-stable laser to 3 pairs of Zeeman-components of the ion.
As previously, this is a complex experiment so it may fail at any time,
enjoy it while it lasts: https://www.youtube.com/watch?v=hZQtlHXECQ4
The servo that steers the clock-laser onto the clock-transition of the ion
measures quantum jumps on the red and blue side of each Zeeman-peak, and
strives for the same amount of jumps on both sides.
The overlay image cycles between a few different images:
- The clock-transition line-center estimates, based on the mid-point
between a Zeeman pair. Unfortunately this is still in units of the final
double-pass AOM that shifts the clock-laser frequency before the ion. I'll
try to improve this so it relates to the actual optical frequency at 445
THz in the future. - an estimate of the magnetic field (1.2 uT or so), again three separate
estimates based on the Zeeman-pairs. - The 'quantum-jumps' observed on the red and blue side of each transition.
The servo strives for equal amount of jumps on the blue and red side - then
we know we are centered on the peak. You can note how noisy the data is
(with Poisson statistics) when we only have one atom to work with! (Compare
to a Ceasium clock with a SNR of 1e6 (or so I hear))
We roughly checked the observed line-center against the drift-model for one
of our active Hydrogen-masers and so far they agree to about 3e-15. The
BIPM SRS recommended frequency is given with an (conservative?) uncertainty
of 1.5e-15 [1]
regards,
Anders
[1] https://www.bipm.org/utils/common/pdf/mep/88Sr+_445THz_2017.pdf
On Fri, Dec 6, 2019 at 5:39 PM Anders Wallin anders.e.e.wallin@gmail.com
wrote:
Hi all, you may find our live-stream from the lab amusing:
https://www.youtube.com/watch?v=z9VFbs4FogY
The central bright dot is fluorescence at 422nm from laser cooling a
single trapped 88Sr+ ion. The ion emits about 1e7 photons/s at most and we
currently detect about 500 of those in a 20ms detection window (using a
Hamamatsu PMT module).
The bar-chart shows the clock-transition spectrum at 445 THz (674nm). The
X-axis is a drive-frequency to the last AOM that shifts the clock-laser
frequency to coincide with the ion frequency. The frequency around 75.9MHz
should be doubled to get the real optical frequency-shift (double-pass AOM).
We 'shoot' 100 pulses at each clock-laser frequency towards the ion, and
detect how many times we are able to drive the ion into the 'dark'
clock-state. The clock state is long-lived (400ms or so), and detection is
by turning on the cooling and noticing that the ion is dark. In theory the
ion should blink in the camera-view also, but the exposure-time is now long
enough that there is not much visible blinking.
The height of the bars show that we are able to excite the
clock-transition with about 20-30% probability at the moment.
The clock-transition splits into five symmetric Zeeman pairs, four of
which are observed in this scan range. We have two magnetic shields and
compensating electromagnets to reduce the DC magnetic field to 0.4 uT or
so. This splits the outermost components by about 20kHz (10kHz AOM-range in
the figure, doubled). The line-center is around 75.945 MHz on the AOM. This
corresponds to the clock-transition center, 444 779 044 095 486.5 Hz. Maybe
we should make this more obvious, an AOM number like 75 MHz is not so
impressive...
The peaks are now around 500Hz wide. This is about 1e-12 fractional. There
is room for improvement as the 88Sr+ clock-state natural lifetime of 400ms
only limits linewidth to 4Hz or so... Line-center (the middle of all zeeman
peaks) can be determined more precisely than linewidth.
The control system (ARTIQ) is now just repeating the same scan over and
over, takes around 1h per scan (12kHz range with 25Hz resolution IIRC), and
each new spectrum is plotted with a new color.
Enjoy it while it lasts - this is a live stream and anything may happen
(cooling laser unlocks from Rb-cell, clock-laser unlocks from ULE-cavity,
ion disappears, whatever....). Ion storage times have been in the ~4 days
range previously - so I am hoping it will run nice now for 24h or so.
Final clock-operation will not scan this thoroughly over all the peaks,
just three of them, and just one frequency on the left/right side of each
peak - and then a numerical servo locks on to the center of each peak.
If you run an optical clock I hereby challenge you to live-stream it and
post here!
cheerio,
Anders
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On 4/23/20 8:36 AM, Bob kb8tq wrote:
Hi
Very cool !!!
Sort of sounds like we will not be doing this in a basement lab any time soon :(
Bob
Not in a home basement lab, anyway. I'm sure there's some facilities
around the world with clocks in a basement (for temperature stability,
etc.) <grin>
On Apr 23, 2020, at 11:27 AM, Anders Wallin anders.e.e.wallin@gmail.com wrote:
Today (a mere 4-and-a-half months since my post below) we managed to lock
the ultra-stable laser to 3 pairs of Zeeman-components of the ion.
As previously, this is a complex experiment so it may fail at any time,
enjoy it while it lasts: https://www.youtube.com/watch?v=hZQtlHXECQ4