Réunion erc. Gwendal Fève. Panel PE3 12 mn presentation 12 mn questions

Transcription

1 Réunion erc Gwendal Fève Panel PE3 12 mn presentation 12 mn questions

2 Electron quantum optics in quantum Hall edge channels Gwendal Fève Laboratoire Pierre Aigrain, Ecole Normale Supérieure-CNRS Professor at University Pierre et Marie Curie 36 years, 36 publications, 1000 citations /2001: 1 year internship at Stanford University (theory) /2006 : PHD Ecole Normale Supérieure (exp.) /2007 : Postdoc LPN Marcoussis (nanofabrication) : Team-leader at Laboratoire Pierre Aigrain: electron quantum optics

3 Motivation, electron optics ballistic and coherent conductors on a few microns length! Quantum electronics: propagation of coherent electron beams mirror mirror I1( t) I2( t') Source 1 : Detector : Detector 1 : beam splitter I(t) Source 1 : I 2 ( t') Source 2 : Detector 2 : Source 2 : Mach-Zehnder interferometer coherence and statistical properties of light sources Hanbury-Brown and Twiss interferometer wave-like/ corpuscular-like descriptions

4 A starter: the electronic Mach-Zehnder interferometer Chirality matters! Quantum Hall edge channels are a model system Gaz 2D B V Y. Ji et al., Nature 422, 415 (2003) 1m V G V G(mV) V G(mV)

5 Single particle or many-body? V Gaz 2D B Contrast 60% 1m V G Contrast of interferences depends on the size of the interferometer! P. Roulleau et al., Phys. Rev. Lett. 101, (2008) Major difference with optics : Coulomb interaction + Fermi sea Emergence of collective eigenmodes (several electron/ hole pairs): charge density waves Interferences are understood in a single particle description Competition between single particle and many-body physics

6 A new resource : the single electron emitter V G ev exc(t ) V G Ideal tool to test the limits of single particle description Source initializes a well defined single particle state n Emitted state G. Fève et al., Science 316, 1169 (2007) Interaction leads to quasiparticle destruction D. Ferraro,.., G. Fève,.., PRL 113, (2014) n After interaction e/h pairs relaxation 0 0

7 The project Test the limit of the single particle description Picture the wavefunction of a single electron Observe the life and death of a single electron Control and limit decoherence effects Probe the coherence of few (two) particle states Post-selection of entangled electron pairs in a Franson interferometer Probe the regime of strong interactions: the fractional quantum Hall effect Can we emit a single quasiparticle of fractional charge? And probe fractional statistics in electron quantum optics setups?

8 The electronic Hong-Ou-Mandel interferometer 3 S34( t, t') * * S34( t, t') 1 ( t') 1( t) 2( t') 2 ( t) Source 1 4 S 1 0) dtdt' S ( t, ') T 34( 34 t meas Source Undistinguishable photons Undistinguishable fermions C. Hong et al., PRL 59, 20 (1987) E. Bocquillon,, G. Fève, Science 339, 1054 (2013)

9 HOM interferometry, a swiss army knife for EQO HOM interferometer probes the coherence of input states Can we picture single particle wavefunction (tomography)? Engineer single particle states? Observe and control decoherence? C. Grenier,.., G. Fève,.. New J. Phys. 13, (2011) T. Jullien et al., Nature 514, (2014) Source 1 I ( t 3 ) 3 4 I 4 ( t') Interaction medium Integer edge channels Source 2 V ac (t) +V dc

10 HOM interferometry, a swiss army knife for EQO HOM interferometer probes the coherence of input states HOM interferometer probes the indistinguishability of states Can we generate indistinguishable states? Can we use it to postselect entangled electron states? Which degree of entanglement can we reach? J. Splettstoesser et al., Phys. Rev. Lett. 103, (2009) Source f X S T s Source P 34 Time-bin entanglement f,3 s,4 s,3 f,4 ( 1 ) cos( 1 2 )

11 HOM interferometry, a swiss army knife for EQO HOM interferometer probes the coherence of input states HOM interferometer probes the indistinguishability of states Random partitioning probes the charge of excitations HOM interferometry is sensitive to the statistics: Can we generate on demand single quasiparticles of fractional charge? Fermions Bosons What about anyons? Source 1 dot or antidot I ( t 3 ) 3 4 I 4 ( t') Interaction medium Fractional edge channel Source 2

12 Conclusion / Experimental techniques Test the limit of the single particle description Picture single electron wavefunction, control of decoherence Probe the coherence of two-particle states On-demand emission of entangled electron pairs Probe the regime of strong interactions: the fractional quantum Hall effect Emission of fractional excitation, probe anyonic statistics AC current measurements (GHz), ~100 pa Noise measurements (MHz), ~10-31 A 2.Hz -1 Characterization of emitters G. Fève et al., Science 316, 1169 (2007) Measurement of interaction parameters E. Bocquillon,.., G. Fève, Nat. Comm. 4, 1839 (2013) Two-particle interferences E. Bocquillon,, G. Fève, Science 339, 1054 (2013) Determination of quasiparticle charge E. Bocquillon,..., G. Fève, PRL 108, (2012) (integer case)

13 Conclusion / Environment Test the limit of the single particle description Picture single electron wavefunction, control of decoherence Probe the coherence of two-particle states On-demand emission of entangled electron pairs Probe the regime of strong interactions: the fractional quantum Hall effect Emission of fractional excitation, probe anyonic statistics Location Physics department of Ecole Normale Supérieure Team 4 PHDs in 5 years (experiments) Environment Electronic transport: J.M. Berroir, B. Plaçais, T. Kontos Quantum optics: LPA (C. Diederichs), LKB (C. Fabre, N. Treps) Theory: LPA (C. Mora, N. Regnault), ENS Lyon (P. Degiovanni), CPT Marseille (T. Martin) 1 postdoc, 2 years (theory) Samples LPN Marcoussis (U. Genser, Y. Jin, A. Cavanna)

14 Franson interferometer Source 1 1 f 3 X S T s Source P 34 Time-bin entanglement f,3 s,4 s,3 f,4 ( 1 ) cos( 1 2 )