[time-nuts] Thinking outside the box a super reference

Bruce Griffiths bruce.griffiths at xtra.co.nz
Fri Nov 4 19:30:17 EDT 2016

The N resonance discussedd in:http://walsworth.physics.harvard.edu/publications/2005_Smallwood_HUBAThesis.pdf

May be a better bet than traditional CPT.

    On Saturday, 5 November 2016 12:17 PM, Magnus Danielson <magnus at rubidium.dyndns.org> wrote:


On 11/05/2016 12:04 AM, Poul-Henning Kamp wrote:
> --------
> In message <59dc074a-3a09-6315-29d4-6877c3bf7510 at rubidium.dyndns.org>, Magnus Danielson write
> s:
>>> With respect to precision machining, that space has changed a lot
>>> over the last five years, with precision CNC machines, factory
>>> or home-built, dropping dramatically in price.
>> You need to tune it regardless.
> First:  Yes, but if you pick a sensible vibration mode for your
> microwave resonance, that can be done with an screw-in endcap.


> Second:  No, I would actually not need to tune it.
> Historically resonance cavities were used so that step/avalance
> diode multipliers had enough power to excite them.  Today we have
> semiconductors which work at those frequencies.
> Later people kept the resonance, because it works well with low
> power budgets in telecoms/milspec applications.
> But the resonanance leads to all sorts of trouble, including frequency
> pulling, temperature sensitivities etc.
> We're neither space nor power constrained, we'd probably be
> perfectly happy if the end result is 4U and 100W, so resonance
> is not mandatory.

Sure, but if you do have a cavity, as you was hinting at, tuning it is 
still needed for the cavity pull effect.

> Third:  A lot of the "everybody knows" about which atoms can be
> used for active vs. passive atomic standards comes from the
> state of the art electronics about 30 years ago.

Sure, but some behaviors just remains there when still using such setups.

> Using laser-pumping and modern semiconductors, it might actually
> be possible to detect the 6.8GHz photons from the Rb.
> They won't be coherent photons, like in a Hydrogen maser, but we
> don't need them to be, in fact that just causes the same exact
> problems as the tuned cavity anyway, as long as we can measure
> the frequency well enough.

You can avoid the cavity using sidebands of the pumping laser and all 
that, yes I know.

Active maser like the hydrogen would be possible naturally, but would 
require the resonator.

A passive direct observation would also possible, but detection will be 
harder and then you would run into S/N issues.

> (No, I havn't done the math on this, my wife has banned me from
> starting any new projects until our house is finished.)

Probably a wise thing.

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