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UID:0-1159@lptms.universite-paris-saclay.fr
DTSTART;TZID=Europe/Paris:20261006T110000
DTEND;TZID=Europe/Paris:20261006T120000
DTSTAMP:20261005T075952Z
URL:http://www.lptms.universite-paris-saclay.fr/seminars/lptms-seminar-tbc
 /
SUMMARY:LPTMS Seminar: Hugo Girin - Salle des séminaires du FAST et du LPT
 MS\, bâtiment Pascal n°530 - 6 Oct 26 11:00
DESCRIPTION:Graphs on Chip\nHugo Girin (C2N\, Palaiseau)\n&nbsp\;\n\nA wave
  graph is a network of one-dimensional bonds—optical waveguides\, microw
 ave cables\, quantum wires—connected at vertices where waves scatter [1]
 . Despite this simple structure\, wave graphs are one of the cleanest play
 grounds for quantum chaos: every eigenmode and scattering property can be 
 computed exactly\, while the underlying classical dynamics can be tuned fr
 om regular to fully chaotic by the topology alone. In the chaotic regime\,
  the spectrum follows the universal statistics of random-matrix theory\, a
 nd eigenfunctions spread uniformly across the graph [2]. Yet decades after
  these predictions\, their experimental test has remained confined to micr
 owave networks [3\, 4].\n\nWe implement wave graphs on a silicon photonic 
 chip [5]\, operating at telecom wavelength and room temperature (Fig. 1(a)
 ): graph bonds are silicon waveguides\, connected by 2:2 directional coupl
 ers. Injecting laser light through a lensed fiber\, we exploit high-Q reso
 nances (up to 2 × 105) to resolve ∼ 850 modes (Fig. 1(b)): a chaotic gr
 aph reproduces the predicted universal statistics\, while a non-chaotic on
 e does not—the first on-chip verification of this cornerstone of quantum
  chaos.\n\nSpectral statistics\, however\, only probe the spectrum as a wh
 ole—they say nothing about what a single wavefunction actually looks lik
 e. To see chaos directly\, we exploit silicon’s optical nonlinearity to 
 image the intracavity field itself: near-field third-harmonic generation m
 aps its intensity across the graph with sub-wavelength resolution (Fig. 1(
 c\,c’)). Resonances less than a nanometer apart display starkly differen
 t intensity landscapes across the same network—a direct\, real-space vie
 w of the mode-to-mode fluctuations that random-matrix theory predicts only
  on average.\n\nThis integrated\, room-temperature platform turns wave gra
 phs into a versatile\, scalable tool. In this talk\, I will discuss how it
  opens the door to engineering topology and disorder at will\, and to cont
 rolling chaotic light transport with nonlinearity.\n\nReferences\n[1] T. K
 ottos and U. Smilansky. Quantum Chaos on Graphs. Phys. Rev. Lett. 79(24).\
 n[2] Z. Pluhař and H. A. Weidenmüller. Universal Quantum Graphs. Phys. R
 ev. Lett. 112(144102).\n[3] O. Hul\, S. Bauch\, P. Pakoński\, N. Savytsky
 y\, K. Życzkowski\, and L. Sirko. Experimental Simulation of Quantum Grap
 hs by Microwave Networks. Phys. Rev. E 69(056205).\n[4] B. Dietz\, T. Klau
 s\, M. Masi\, M. Miski-Oglu\, A. Richter\, T. Skipa\, and M. Wunderle. Clo
 sed and Open Superconducting Microwave Waveguide Networks as a Model for Q
 uantum Graphs. Phys. Rev. E 109(034201).\n[5] H. Girin\, X. Chécoury\, B.
  Odouard\, S. Bittner\, J.-R. Coudevylle\, B. Dietz\, C. Lafargue\, and M.
  Lebental. “Graphs on Chip: A Silicon Photonics Platform”. arXiv:2605.
 12538. 2026. arXiv: 2605.12538\n\n&nbsp\;\n\nAbstract
CATEGORIES:seminars
LOCATION:Salle des séminaires du FAST et du LPTMS\, bâtiment Pascal n°53
 0\, rue André Riviere\, Orsay\, 91405\, France
X-APPLE-STRUCTURED-LOCATION;VALUE=URI;X-ADDRESS=rue André Riviere\, Orsay\
 , 91405\, France;X-APPLE-RADIUS=100;X-TITLE=Salle des séminaires du FAST 
 et du LPTMS\, bâtiment Pascal n°530:geo:0,0
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