[Qirg] Re: New I-D: Timing Regimes in Quantum Networks and their Physical Underpinnings

[Rod Van Meter <[e-mail]>]

Doh, Oskar sent this directly to Michal and me, not to QIRG, and without 
thinking I cced QIRG on the reply. Oskar, my apologies -- hope you don't 
mind too much! Fortunately I think there are only good, general 
comments, nothing private in this.

--Rod

On 2026/03/04 13:48, Rod Van Meter wrote:
>
>
> On 2026/03/03 23:42, Deventer, M.O. (Oskar) van wrote:
>>
>> Dear Michal, (Rod),
>>
>> The document is very useful. It provides common understanding of the 
>> different timing regimes. As each of those timing regimes may involve 
>> future standards, this is good reference material for standardisation 
>> roadmaps. One of those is the European CEN-CENELEC JTC22 roadmap 
>> <https://www.cencenelec.eu/media/CEN-CENELEC/AreasOfWork/CEN-CENELEC_Topics/Quantum%20technologies/Documentation%20and%20Materials/fgqt_q06_standardizationroadmapquantumtechnologies_release1-1.pdf>, 
>> of which a new release is being developed.
>>
> Thanks!
>
> Michal and I both participated in a workshop on standardization for 
> quantum at least year's IEEE QCE (Quantum Week). I think this document 
> was mentioned there -- certainly JTC22 was. A lot of what was 
> discussed there was about computing, not networking, but I see this 
> document includes some on networks as well.
>
>> Here are some minor points that you may consider for a future version.
>>
>>   * Sections 3.3.3 and 3.4.1 use Gaussian wavepackets for
>>     illustration. Whereas they satisfy for illustration purposes, in
>>     practice (physics) wavepackets are typically exponentially
>>     decaying. This is because of the physical processes that generate
>>     them: an excitation followed by an exponential decay (e.g.
>>     NV-center, SPDC).
>>
> Thanks.
>
> Yes, we used Gaussians there, but we're actively considering a richer 
> vocabulary for how to write down the wave packet envelope shape. For 
> the pulses used to control ion traps and superconducting systems, one 
> community uses a digitally sampled shape, the other uses splines; we 
> are considering whether/how to adopt either of those approaches. 
> You'll see some of that in some of our upcoming documents over the 
> next few months.
>
> (FWIW, we believe the photons we are generating in our lab *are* 
> Gaussian, but we know that e.g. Tracy Northup's ion trap-generated 
> photons are very, very different -- they look like an Erlang function.)
>
>>  *
>>
>>
>>   * Section 4 presumes single-detector SPDs. Multiplexed SPDs have
>>     the incoming photons (passively) distributed over an array of
>>     SPDs. Subsequent photon are likely to hit a different SPD. This
>>     changes how the different time metrics should be determined or
>>     interpreted.
>>
> We aren't (or at least I'm not -- I shouldn't speak for Michal) 
> familiar with muxed SPDs, but we don't want to get too far into the 
> characteristics of specific devices here; instead, the goal here is to 
> show the characteristics can be described in a common language.
>>
>>  *
>>
>>
>>   * Section 5.2.1 highlights trapped-ion-based quantum memories, and
>>     its timing regime. Another type of quantum memory uses atomic
>>     frequency comb (AFC). It has different timing properties.
>>
> Ditto here.
>>
>>  *
>>
>>
>>   * Sections 3 and 5.3 describe photonic qubits that are dual-rail
>>     polarization encoded.
>>       o Another prominent encoding is dual-rails time-bin (already
>>         mentioned in 3.1). The math is more-or-less the same.
>>         However, there are stringent timing requirements on the
>>         unbalanced interferometer used for their measurement.
>>       o There is also single-rail (Fock-state, number-state)
>>         encoding. Same HOM-timing requirements, but likely not so
>>         relevant in the QIRG context.
>>
> Yeah, somewhere we need more on how to describe photons and photonic 
> qubits. This document is probably not the right place to do it. (We 
> have another document in progress, but still only in very early 
> stages, on this; QIRG/IRTF might not be the right place for that, but 
> we're not sure where is.)
>>
>>      o
>>
>>
>>       o The description of the slowly rotating motor-controlled
>>         HWP/QWP is instructive. Other polarization controllers
>>         (squeezer-based, integrated optical) operate much faster.
>>
> Would love to talk to you about these differences for our own 
> research/implementation purposes, but don't want to get too far into 
> the hardware details here.
>
>
> Thanks,
>
>
> --Rod
>
>
>
>>      o
>>
>>
>>
>>
>> Best regards,
>>
>> Oskar
>>
>> Dr. ir. M.O. (Oskar) van Deventer
>> Chair CEN-CENELEC JTC22 on
>> Quantum Technologies
>>
>> 	
>>
>> T [phone]
>> M [phone]
>> E [e-mail] <mailto:[e-mail]>
>>
>> 	
>>
>> Location <http://www.tno.nl/locaties/DHA>
>>
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>>
>> Read release 1.1 of the CEN-CENELEC Standardisation Roadmap on 
>> Quantum Technologies 
>> <https://www.cencenelec.eu/media/CEN-CENELEC/AreasOfWork/CEN-CENELEC_Topics/Quantum%20technologies/Documentation%20and%20Materials/fgqt_q06_standardizationroadmapquantumtechnologies_release1-1.pdf>.
>>
>> *From:*Michal Hajdušek <michal=[e-mail]>
>> *Sent:* dinsdag 3 maart 2026 03:30
>> *To:* [e-mail]
>> *Cc:* Rodney Van Meter <[e-mail]>
>> *Subject:* [Qirg] New I-D: Timing Regimes in Quantum Networks and 
>> their Physical Underpinnings
>>
>> Dear QIRG members,
>>
>> It is with great pleasure that we would like to introduce our new 
>> Internet Draft called "Timing Regimes in Quantum Networks and their 
>> Physical Underpinnings". The I-D can be found here:
>> https://datatracker.ietf.org/doc/draft-hajdusek-qirg-timing-physics/
>>
>> This is not a typical I-D, both in terms of content and format so we 
>> would like to make a few disclaimers that will hopefully clarify any 
>> potential confusion.
>>
>> Goal:
>> This draft is intended to be a first in a sequence of drafts. Its 
>> purpose is to discuss relevant physical phenomena related to timing 
>> regimes in quantum networks. Therefore, there are quite a number of 
>> equations but there are no engineering decisions. Those will be 
>> presented in upcoming drafts that we are working on. The purpose of 
>> this draft is to serve as a bridge between the more abstract 
>> discussion of RFC9340 and concrete design choices of these planned 
>> drafts.
>>
>> Format:
>> Given that we have used more than a typical number of equations, the 
>> plain txt and pdf versions may be difficult to read in some places. 
>> We are working on making the mathematical expressions more 
>> reader-friendly. The HTML version is in our opinion the most readable 
>> at the moment.
>>
>> Future:
>> Current draft at
>> https://github.com/moonshot-nagayama-pj/draft-hajdusek-qirg-timing-physics
>> does not contain any figures. However, a figure is worth a thousand 
>> equations, or something like that. Our plan is to include figures in 
>> the next version. If you would like to see the planned figures, you 
>> can visit an older version that the current draft builds on:
>> https://github.com/moonshot-nagayama-pj/public-documents/tree/main/timing-regimes
>> We also intend to expand the discussion on how to read the equations 
>> and how to turn them into physical-layer specifications, protocol 
>> messages, timing constraints and code.
>>
>> What we would like:
>> Your frank opinions. This draft is an ambitious undertaking, and we 
>> are certain there are topics that are either underdeveloped, 
>> misleading or outright missing. We would also like your help in 
>> making the text accessible to IETF/IRTF audience. We are also happy 
>> to expand the author list if people make contributions to the draft.
>>
>> We look forward to hearing your opinions, either via the mailing list 
>> or in Shenzhen.
>>
>> Best regards,
>> Michal and Rod
>>
>
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