During the third reporting period (M36–M60), we successfully achieved most of the initial goals set by UltraFastNano. Below, we highlight the main accomplishments of RP3.
WP1:
- A phase stable voltage pulse generator based on a frequency comb has been realized that allows to generate very clean voltage pulses with a temporal width down to 20 picoseconds. This generator is presently used in WP3 to realize quantum interference experiments (Aluffi et al., Phys. Rev. Applied 20, 034005 (2023)).
- Single-shot detection of flying electrons using a single-triplet double quantum dot has been achieved (Thiney et al., Phys. Rev. Research 4, 043116 (2022)).
- Fabrication of lateral p-n junction has been completed and electroluminescence from the junction at low temperature has been demonstrated (publication: Semicond Sci. Technol. 38, 065001 (2023)).
- Detection of single charges in a high magnetic field: We have successfully verified the cryogenic detection of charge using a 4 Kelvin HEMT cryo-amplifier positioned just a few millimeters from the sample, achieving minimal heating of 200mK. The now ultra-small input capacitance of 0.5pF is expected to facilitate the detection of a single charge.
WP2:
- Ultrafast voltage pulses down to 2.3 picoseconds at cryogenic temperatures have been generated using opto-electronic conversion. Tunnel oscillations in a quantum device have been observed at a temperature as high as 4K.
- Electron injection from continuous hot-electron source into a p-n junction has been demonstrated. Electroluminescence from hot electrons has been observed. (Norimoto et al.)
- Light collection efficiency from a p-n junction has been improved above the dark count rate of single-photon detectors.
WP3:
- Realization of the first quantum interference with ultrashort voltage pulses (Ouacel et al.).
- Demonstration of the practical feasibility of time braiding at filling factor 2/5 using our novel two-particle dynamical interferometry, while at 2/3, hole-conjugate FQHE phases present challenges for braiding (Glattli et al.).
- Development of a new model for edge channel physics at ν=2/3 that revealed poor coherence lengths in our experiments, with both studies currently under review (Glattli et al. 2).
WP4:
- Interaction effects on the emission and propagation of quasiparticles have been reported on (Schulenborg et al. Phys. Rev. B 109, 115433 (2024)).
- Dynamics of quasiparticles in interferometers has been reported on: (1) Spånslätt et al., Phys. Rev. B 110, 075431 (2024)) ; (2) S. Varada, C. Spånslätt, M. Acciai, to be submitted (3) T. Kloss, X. Waintal, to be submitted.
WP5:
- Progress meetings led on Sept 5-6th, 2024 (Teddington, UK) and March 30th, 2023 (La Thuile, Italy, during Moriond Conférence). The RP3 (and closure) project meeting was held virtually on February 25, 2025,
- In terms of communication activities during RP3: 2 articles for public audience, presentations at 13 international conferences, 29 workshops and seminars, 8 articles submitted, 32 articles published during the entire project duration, multiple actions for scientific vulgarisation (with especially 1 animated movie broadly shared on social media and public audience events),
- In terms of exploitation, several paths have been identified and pursued, either by commercial actions, services for fees, or patents filed.