[Qirg] Re: Qirg Digest, Vol 94, Issue 3

[Wenji Wu <[e-mail]>]

I took a quick look at "Timing Regimes in Quantum Networks and their
Physical Underpinnings", i would suggest adding a session to discuss
different types of wavepackets. For photons emitted from cavity-based
trapped ions, the wave packet duration can be dozens of microseconds. On
the other hand, the wavepacket duration of photons from SPDC can be at the
picosecond level. The timing and control requirements for different types
of photons are quite different. For the cavity-based trapped ions case, the
timing requirement is not demanding while there is a strict real-time
control requirement for the SPDC case.

On Wed, Mar 4, 2026 at 1:09 AM <[e-mail]> wrote:

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>    1. Re: New I-D: Timing Regimes in Quantum Networks and their Physical
> Underpinnings
>       (Rod Van Meter)
>
>
>
> ---------- Forwarded message ----------
> From: Rod Van Meter <[e-mail]>
> To: Rod Van Meter <rdv=[e-mail]>, "Deventer, M.O.
> (Oskar) van" <[e-mail]>, "Hajdušek, Michal" <
> [e-mail]>
> Cc: "[e-mail]" <[e-mail]>
> Bcc:
> Date: Wed, 4 Mar 2026 16:09:19 +0900
> Subject: [Qirg] Re: New I-D: Timing Regimes in Quantum Networks and their
> Physical Underpinnings
>
> 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.
>       - 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.
>       - 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.)
>
>
>    -
>       - 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
>
>
>
>
>    -
>
>
>
> Best regards,
>
>
>
> Oskar
>
>
>
>
>
> Dr. ir. M.O. (Oskar) van Deventer
> Chair CEN-CENELEC JTC22 on
> Quantum Technologies
>
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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]>
> <michal=[e-mail]>
> *Sent:* dinsdag 3 maart 2026 03:30
> *To:* [e-mail]
> *Cc:* Rodney Van Meter <[e-mail]> <[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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