Multiphotonics (2025)

The second MULTIPHOTONICS meeting will take place in Madrid, on 8–9 October (2025) with the support of ICMM—CSIC and IFF—CSIC. It follows the very successful MULTIPHOTONICS (2024) first edition. The workshop will likewise discuss the physics of multiphoton correlations.

If you liked Munich, you'll love Madrid!

Topics

Multiphoton generation: Single and $N$-photon emission.
Quantum light generation with properties such as entanglement or squeezing.
Frequency filtering, statistics, coherence and correlation measurements.
Quantum optics, cavity-QED, light-matter interaction and nanophotonics.

Venue

ICMM-CSIC on the Cantoblanco Campus:

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Hotel accommodation

External attendants will be provided with a two-nights (Tue 7 & Wed 9) hotel room with breakfast at the VP Jardín De Tres Cantos in Tres Cantos. This is a quiet, modern urban-planning city at the north of Madrid, well connected to the site of the meeting and to the Spanish capital itself.

Organizers

The event is supported by a joint ICMM‒IFF effort:

• Fabrice Laussy from ICMM‒CSIC.
• Carlos Sánchez Muñoz from IFF‒CSIC.

Contact the organizers.

Confirmed Attendants

1. Serge Reynaud^* - Laboratoire Kastler Brossel, Paris
2. Sven Höfling - University of Würzburg, Würzburg
3. Jesper Mørk - Technical University of Denmark, Copenhagen
4. Zhiliang Yuan - Academy of Quantum Information Sciences, Beijing
5. Kai Müller - Technische Universität München, München
6. Tim Thomay - University at Buffalo, New York
7. Ahsan Nazir - University of Manchester, Manchester
8. Jake Iles-Smith - University of Sheffield, Sheffield
9. Philipp Schneeweiß - Humboldt-Universität zu Berlin, Berlin
10. Vincenzo D'Ambrosio - Università di Napoli Federico II, Napoli
11. Владислав Шишков (Vladislav Shishkov) - Aalto University, Espoo
12. Juan Camilo López Carreño - University of Warsaw, Warsaw
13. Yajun Wang - Shanxi University, China
14. Alexandros Spiliotis - IESL-FORTH, Heraklion
15. Natalia Armaou - Westlake University, China
16. Moritz Meinecke - University of Würzburg, Würzburg
17. Carlos Antón Solanas - Universidad Autónoma de Madrid
18. Johannes Feist - Universidad Autónoma de Madrid
19. Antonio Isaac Fernandez Dominguez - Universidad Autónoma de Madrid
20. Alejandro González Tudela - IFF-CSIC, Madrid
21. Eduardo Zubizarreta Casalengua - Technische Universität München, München
22. Sang Kyu Kim - Technische Universität München, München
23. Joaquin Guimbao Gaspar - ICMM-CSIC, Madrid
24. Jacob Ngaha - ICMM-CSIC, Madrid
25. Lukas Hanschke - Technische Universität München, München
26. Elena del Valle - Universidad Autónoma de Madrid
27. Carlos Sánchez - IFF-CSIC, Madrid
28. Fabrice Laussy - ICMM-CSIC, Madrid

Tentative Program

Tuesday 7 October

Participants arrive.

Wednesday 8 October (Day 1)

Morning Session

Opening (by Fabrice Laussy)

8:50-9:00

Serge Reynaud

9:00-9:30

Kai Müller

Unlocking multiphoton emission from a single-photon source through mean-field engineering — 9:30-10:00

Multiphotons are generally regarded as accidental in the context of single photon sources. However, multiphoton emission can turn out to be even more fundamental and interesting than the single-photon emission, since in a coherently driven system, the multiphoton suppression arises from quantum interferences between virtual multiphoton fluctuations and the mean field in a Poisson superposition of all number states. Here, we demonstrate how one can control the multiphoton dynamics of a two-level system by disrupting these quantum interferences through a precise and independent homodyne control of the mean field. We show that, counterintuitively, quantum fluctuations always play a major qualitative role, even and in fact especially, when their quantitative contribution is vanishing as compared to that of the mean field.

Joaquin Guimbao Gaspar

10:00-10:30

Juan Camilo López Carreño

10:30-11:00

Coffee break

Post-coffee

Jesper Mørk

Quantum noise and squeezing in nanolasers. — 11:30-12:00

We present a recently developed method for simulating quantum noise in nanolasers. Based on a simple stochastic interpretation of rate equations, the approach accurately reproduces quantum master equation results for few-emitter lasers and aligns with Langevin equations in macroscopic regimes. Notably, it bridges the intermediate mesoscopic regime previously inaccessible to existing models. We apply this method to analyze amplitude squeezing in nanolasers using novel cavities with extreme light confinement, which strongly enhance light-matter interaction.

Elena del Valle

12:00-12:30

Ahsan Nazir

12:30-13:00

Владислав Шишков

Spectral theory and statistical properties of integrated single-photon sources. — 13:00-13:30

Lunch at El Goloso — 13:30-15:00

Group photo

Afternoon Session

Philipp Schneeweiß

Tailoring photon statistics with an atom-based two-photon interferometer — 15:00-15:30

Based on Ref. .

Johannes Feist

15:30-16:00

Lukas Hanschke

16:00-16:30

Jacob Ngaha

16:30-17:00

Coffee break

Evening Session

Jake Iles-Smith

17:30-18:00

Antonio Isaac Fernandez Dominguez

18:00-18:30

Yajun Wang

18:30-19:00

Carlos Sánchez

19:00-19:30

20:30 Dinner

Thursday 9 October (Day 2)

Morning Session

Sven Höfling

9:00-9:30

Moritz Meinecke 

9:30-9:50

Tim Thomay

Higher-order Fock states for sensing applications. — 9:50-10:20

See Ref. .

Eduardo Zubizarreta Casalengua

10:20-10:50

Coffee break

Post-Coffee Session

Zhiliang Yuan

11:15-11:45

Carlos Antón Solanas

11:45-12:15

Sang Kyu Kim  

12:15-12:35

Alejandro González Tudela

12:35-13:05

Lunch

Afternoon Session

Vincenzo D'Ambrosio

Tailoring spatial correlations with structured light — 14:00-14:30

Alexandros Spilioti

14:30-15:00

Natalia Armaou 

Spatial correlations of opposite OAM states of light — 15:00-15:20

Fabrice Laussy

Liquid time and time liquids — 15:20-15:50

The basic quantum-optical emitter—the two-level system—is already much more complicated than one could reasonably expect, and to this day, its thorough characterization remains to be completed. Here, I will jump to the case of the $N$-level system, and survey the amazing phenomenology that immediately shouts out from this simplest extension of the brick of quantum optics. A first surprise is that the $N$-level system, not the two-level one, is the most suitable to implement perfect single-photon sources. Furthemore, a good single-photon source acquires features that differ considerably from those usually wanted for that purpose. For instance, instead of merely suppressing two-photon coincidences at $\tau=0$, a good single-photon emitter is one that develops long-time oscillations as a result of self-organizing its photon streams to all orders in photon counting, differing from the basic case in a way similar to how a liquid differs from a gas. This calls for revisiting our understanding of single-photon sources, and raise fascinating questions on how they relate, in time, to exotic phase of matters. I will also describe how such a picture extends into multiphotonics, and how one could observe such effects experimentally.

Closing (by Carlos Sánchez)

Goodbye coffee & Merienda

Participants depart

Q&A(bstracts)

At this occasion, we shall try to revive an old format of archiving Scientific debates: instead of publishing proceedings, we will publish the abstract and the (edited) Questions & Answers sessions, which contains information nowhere else to be found.

One picture is worth a thousand words

For the Multiphotonics (2024), each participant contributed a formula, meaningful and/or inspiring for them, characteristic of their contribution to the field or merely illustrating their talk. Interestingly, there was no degeneracy: Rempe provided the Jaynes-Cummings Hamiltonian, someone went for the mere harmonic oscillator (but wasn't Dirac saying it was enough to understand this?), I (Fabrice) offered the dissipative Jaynes-Cumming ladder formula, which I still haven't found in any publication earlier to mine, Eduardo provided the two-photon spectrum of resonance fluorescence, which produces the logo of the meeting. It was a nice way to make a logo.

For this edition, we'd like to try the same thing but with a figure instead of a formula. This could be a graph, a density plot, the sketch of a concept (artistic or scientific), a diagram, the setup of an experiment, etc., with the same intent of providing a picture—call that a vision if you like—to illustrate the participants' understanding of the topic, ideally with a connection to their talk, even if a remote one. Out of this medley of visual cues to what light-matter interactions is about, we will build the logo of the 2025 meeting.