1. Photon Supression of the shot noise in a quantum point contact Eva Zakka Bajjani Julien Ségala Joseph Dufouleur Fabien Portier Patrice Roche Christian Glattli Yong Jin Antonella Cavanna Nano-electronic group SPEC, CEA Saclay LPN, CNRS, Marcoussis

2. Introduction t (Bandwidth  Quantum Conductor 1. 2.Frequency dependence? 3.Interplay with quantification of electromagnetic energy?

3. Outline 1.Introduction 2.Conductance and zero frequency shot noise of a single mode conductor 3.Finite frequency shot noise 4.From an experimentalist’s point of view 5.Experimental Set up 6.Results 7.Perspectives

4. The wave packet approach Martin and Landauer (1992) Observation time : Emission time : Number of events : Incoming current : 1 channel conductor D Reservoir V I ( i )( t ) ( r )

5. The wave packet approach Martin and Landauer (1992) Observation time : Time scale : Number of events : 1 channel conductor D Reservoir V I ( i )( t ) ( r ) Due to Fermi statistics the incoming current (I 0 ) is noiseless And due to transmission uncertainty :

6. Central limit obey Gaussian statistic New physic for... Probing shorter time scales

7. Finite frequency spectrum Gate Emission of a ‘photon’ V

8. Finite frequency spectrum Gate Emission of a ‘photon’ V

9. Experimental requirements Thermal population of photons negligible  Gate Corresponding wavelength ~ 10 cm  propagation effect have to be taken into account V

10. Coupling to a transmission line Transmitted power: Z s ≈25 kΩ Z o =50Ω   Maximum for

11. First solution: adapt the source impedance to the detection impedance R. J. Schoelkopf et al. Phys. Rev. Lett. 78, 3370 (1997). (Diffusive Conductor R≈50Ω) Advantage: good coupling and sensitivity Disadvantage: many modes, impossibility to tune their transmission. Feedback of amplifier? Quantitative agreement with theoretical predictions, with T e =100 mK (T fridge =40 mK)

12. Second solution: on chip detection E. Onac et al. Phys. Rev. Lett. 96, 176601 (2006). Advantage: good coupling to a high impedance (single mode) source Disadvantage: coupling constant and bandwidth unknown Photocurrent Q D(1-D) Onset current 4 times higher than expected

13. Third solution: adapt the detection impedance Quarter wavelength impedance adapatation

14. Implementation Bias T k≈1.4, Z eff ≈200Ω DC Bias

15. Experimental Set-up V 60 mK 800 mK 4 K 300 K Accordable Filters 4-8 GHz VgVg Shot Noise Shot Noise DC Bias

16. Transmission of the Quantum Point Contact  D 1,D 2,D 3 … (V G )

17. Excess Noise Power at D=1/2

19. Threshold versus frequency

21. Dependence with transmission

22. CONCLUSION We have measured the quantum partition noise of a Quantum Point Contact at finite frequency. Quantitative agreement of the observed shot-noise power dependence with bias voltage and frequency. Our method opens the way to cross-correlation measurements probing the statistical properties of the photons emitted by a phase coherent conductor.

23. Fit with no free paramater, exept coupling

24. Z CZ C R Load = Z C (detector + filter) quantum conductor ( G ) Photon noise = noise of electrical noise power  Can the sub-Poissonian (fermionic) statistics of electrons be imprinted on photons? Yes, provided that only one or two mode are transmitted, and excitation voltage is not too high (Beenaker Schomerus 2004)

25. Room temperature Part

26. Chaîne de détection Generateur de creneaux 60 mK 800 mK 4 K 300 K Lock-in Filtres Accordables 4-8 GHz VgVg

27. Plasmons bidimensionnels Plus concrètement Modèle

28. Experimental requirements Thermal population of photons negligible  Amplifier noise temperature / frequency as small as possible Conductance of the sample independent of bias voltage up to

29. Quarter wavelength impedance adapatation → Reflected wave → Perfect transmission  perfect matching for given frequency  compromise between bandwidth and compensated mismatch

30. Effet de Chauffage? Ordre de grandeur: Pour R mesa =200Ω//200Ω, D=1, eV=100μeV, on obtient T elec =100 mK Le facteur thermique est alors de l’ordre de 0.5, et on obtient

31. Signal attendu Mesa: -3 dB (estimation à partir des courbes G(vG)) Couplage ligne 140Ω/70Ω/50Ω : -2dB (mesure sur une boîte ‘vide’) Attenuation dûe aux câbles: -2 dB (mesures à 4.2K) Circulateurs: 2 X -0.3 dB (idem) I inox:- 0.2 dB (idem)

32. Variation du seuil avec la frequence

33. Est ce bien du bruit de grenaille quantique?

34. Effet de Chauffage?

35. Mesure a differentes frequences