Quantum coherence in semiconductor nanostructures. Jacqueline Bloch

Transcription

1 Quantum coherence in semiconductor nanostructures Jacqueline Bloch Laboratoire of Photonic and Nanostructures LPN/CNRS Marcoussis

2 Laboratoire de Photonique et de Nanostructures Marcoussis A CNRS Laboratory30 km southof Paris 50 permanent researchers Growth facilities Processing facilities Physical studies

3 What are semiconductor nanostructures? e - L x Confine electrons in a volume with dimensions comparable to the De Broglie wavelength (typically 1 nm) Quantum confinement : quantization of the energy levels k = pπ/l Quantum Wells Growth direction 2D Continuum Inter-band transition Intra-band transition Emission

4 What are semiconductor nanostructures? e - L x Confine electrons in a volume with dimensions comparable to the De Broglie wavelength (typically 1 nm) Quantum confinement : quantization of the energy levels k = pπ/l Quantum Dots : 3D confinement TEM G. Patriarche Emission intensity γ 1-10 µev x~ Energie (mev) Discrete quantum states «artificial atom»in a solid state system

5 Optics in microcavities Confine light in small volumes (of the order of λ 3 ) Modify the light matter coupling Interferential mirrors Miroir interférentiel GaAs/AlGaAs Miroir interférentiel Interferential mirrors AlAs n=1 micropillars microdisks Photonic crystal microcavities

6 Quantum coherence in semiconductor nanostructures Control of these quantum emitters, enhance light matter interaction, manipulate single spins - Bose condensates; new optical functionalities - Non-linear optics at the single photon level - Cavity quantum electrodynamics - Quantum information processing - Source of quantum light : quantum cryptography, teleportation

7 GaAs/AlGaAs based structures Semiconductor cavities: a model system to investigate the physics of Bose condensates θ Angle θ (º) K Top DBR Quantum Wells Bottom DBR Emission energy (ev) Microcavity polaritons : mixed exciton-photon states ~ 5meV Upper polariton Lower polariton k in-plane (µm -1 ) Photon Exciton Bosonic quasi-particule (J = +-1) Low effective mass => Large De Broglie wave length => Condensation at high temperature λ T πh = mk BT

8 Bose-Einstein condensation Macroscopic wavefunction λ T πh = mk BT BEC with atoms Cornell s and Wieman s groups: condensation of Rb atoms (1995) Low critical temperatures: < 1 µk T Nature 443, 409 (2006) T = 5 K CdTe Polariton density k y k x Kasprzak et al. Nature, 443, 409 (2006)

9 Typical experimental scheme Far field imaging: k space Near field imaging: real space -0.5 kx Density (µm-1) Far field (d) Energy Flow ky (µm-1) µm Interference with Coherence map a reference beam g(1) Phase dislocations - vortices - solitons kx (µm-1) Resonant injection of polaritons

10 THEORY GROUP at Laboratoire MPQ, Université Paris Diderot Responsable: Prof. Cristiano CIUTI Web page: Google search: Laboratoire MPQ THEORIE Main theoretical activity(semiconductors): - Polariton quantum fluids(photons) - Ultra-strongcouplingin cavityquantum electrodynamics cavité (circuit) Recent review: I. Carusotto& C. Ciuti, Reviews of Modern Physics in press;

11 Alberto Bramati Cavitypolaritons: coherence and spin dynamics Quantum fluid: superfluidity, solitons,.. Spin switch, spin Hall effect Nature Physics 2009 Vortex lattices Nature Physics 2009 Science 2011 Science 2012

12 Jacqueline Bloch Alberto Amo Manipulating Bose condensate in photonic circuits 26 pairs Laboratoire of Photonique and Nanostructures GaAs/GaAlAs microcavities λ/2 cavity 30 pairs Substrate 3x4 GaAs quantum wells Macroscopic propagation and coherence Trapping Ferrier et al. PRL 106, (2011) Galbiati et al. PRL 108, (2012) Wertzet al., Nature Physics6, 860 (2010) Taneseet al. PRL 108, (2012) Wertzet al., PRL to appear

13 Manipulating Bose condensate in photonic circuits Laboratoire of Photonique and Nanostructures What is next? Polariton interferometer Condensation in a periodic potential: Bloch oscillations: H. Flayacet al., Phys. Rev. B 84, (2011) Phys. Rev. B 83, (2011) Propagation, interaction of gap solitons I. Shelykhet al., PRL 102, (2009) Arrays of coupled condensates Bose Hubbard quantum phases Carusotto et al., PRL (2009) Fisher et al., PRB 40, (1989)

14 MPQ Université Paris Diderot Quantum Physics and Devices (QUAD) A. Vasanelli, M. Amanti, S. Barbieri, Y. Todorov, C. Sirtori Building blocks: We develop novel concepts of quantum engineering inmaterialsthatarecurrentlyatthebasisofict. Electron confinement: SemiconductorQWs, band structure engineering Fields of action Photon confinement: plasmonicmicrocavities, highly subwavelength confinement THz quantum cascade laser Electroluminescence from intersubband polaritons S. Barbieriet al. Nature Phot S. Barbieriet al. Nature Phot L. Sapienzaet al., PRL 2008 Y. Todorovet al., PRL 2009 Y. Todorovet al., PRL Integrated quantum cascade laser modulator J. Teissieret al. Opex2012

15 LPQM ENS Cachan Group: Optical propertiesof hybridnanostructures Self-organizedhybridquantum wells: Perovskites (R-NH 3 ) 2 MX 4 a) Photoluminescence Emmanuelle Deleporte (Pr) Jean-Sébastien Lauret(MdC) Strong coupling regime at room temperature Densité optique Tunability PhE-PbI 4 m = 3 m = 2 PhE-PbBr 4 2,40 ev 3,07 ev m = 3 m = 1 m = 2 PhE-PbCl 4 3,65 ev m = 1 Energie (ev) 2,0 2,2 2,4 2,6 2,8 3,0 3,2 3,4 3,6 3,8 4,0 Energie (ev) Objectives : Study of this new material(electronic properties) Polariton condensation Electrical injection M: Pb;X: I, Br, Cl R: Phényl, Cyclohexane. Publications: Superlattices and Microstructures 47, 10 (2010) Appl. Phys. Lett. 93, (2008); New Journal of Physics10, (2008) New Journal of Physics10, (2008) Appl. Phys. Lett. 90, (2007) Phys. Rev. B74, (2006) Appl. Phys. Lett. 89, (2006)

16 Quantum physicswithsingle quantum dots - Single spin in a quantum dot : a quantum bit - Source of quantum light - Cavity quantum electrodynamics using single quantum dot in a cavity

17 A spin in a Quantum dots : a quantum bit? TEM G. Patriarche electron A single spin : a well «isolated»quantum bit? Spin optical pumping : Science 312, 551 (2006), Phys. Rev. Lett. 99, (2007);Nature (2008) Quantum non demolition spin measurement: Science (2006), Nature Physics 3, 101 (2007) Spin coherence: interaction with nuclei Phys. Rev. Lett. 94, (2005), Phys. Rev. Lett. 102, (2009) Nature Physics, 5(8) 2009, Arxiv arxiv: ,

18

19

20 Quantum dots : a solids tate source of quantum light TEM G. Patriarche Luminescence intensity (a. u.) X T=4 K XX Energy (mev) Single photon emission Science 290, 2282 (2000)

21 Semiconductor quantum dots for the generation of non classical states of light Purpose: Efficient indistinguishable single photon source Entanglement of qubits Applications in quantum information ValiaVoliotis, Richard Hostein Resonant Rabi oscillations: qubit initialization Luminescence (arb. units) 0 π 2π 3π 4π 5π P 1/2 (µw 1/2 ) Coherent control of the qubit: θ ψ = cos 0 θ + sin θ: Rabi frequency Pulse area P Indistinguishable single photon sources? increase of T2/T1 HBT on-resonance δ, φ 300 < T 2 < 600 ps (< 2 T 1 ) 600 < T 1 < 900 ps 1 0 µpl Intensity (arb. units) θ =π/2 «off» «on» φ = 0 φ = π Wavelength (nm) Coincidences ,4-12,2 0,0 12,2 24,4 36,6 Retard (ns) (Collaboration: LPA, LPN) HBT on resonance g (2) (0) = 0.06

22 Quantum optics in single quantum dots Optically-gated resonant emission in single quantum dots H. S. Nguyen et al., Phys. Rev. Lett. 108, (2012) Optically-gated resonant emission Optical gate Resonant laser Intensity (10 3 counts/s) Gate ON Gate OFF δ (µev) g (2) (τ) Carole Diederichs Laboratoire Pierre Aigrain τ (ns) τ (ns) τ (ns) τ (ns) Ultra-coherent single photon source H. S. Nguyen et al., App. Phys. Lett. 99, (2011) Norm. intensity g (1) (τ) E - E L (µev) E - E L (µev) E - E L (µev)

23 A quantum dot in a cavity : A solid state system for quantum information processing Contact : Pascale Senellart and Loic Lanco Laboratoire de Photonique et de Nanostructures Marcoussis, France QD g e- cavity mode τ c Optical loss Artificial atom Single photons source Single spin memory Microcavities Controlling spontaneous emission Mixed light-matter states

24 Full control of a single dot spontaneous emission In-situ lithography PL intensity (a.u.) OFF resonance(50k) τ XX τ XX = 1.15 ns ONresonance(5 K) τ XX τ XX = 130 ps time (ns) On demand Purcell effect Light matter entangled states Dousse et al, PRL 2008 Dousse et al, APL 2009 See Dousse et al, Phys. Rev. Lett 2008, APL 2009 Suffczynskii et al, PRL 2009

25 Ultrabright sources for quantum information processing Few photon optical non-linearity Single photons, Indistinguishable photons Entangled photon pairs 0.90 Dousseet al, Nature 2010, Gazzanoet al, 2012 Pulsed excitation Reflectivity photons Incident photons per pulse 10 4 Loo et al, PRL 2012

26 Toward a solid state quantum network? Teleportation, Spin photon entanglement, entanglement distillation, remote spin entanglement, delayed photon entangler Single photon optical switch Spin based quantum memory Delayed photon entangler V Entangled photon pair source Single photon source

27 Optional course: second semestre Laboratoire Photonique et Nanostructures LPN/CNRS Marcoussis ( Laboratoire Matériaux et Phénomènes Quantiques MPQ/ Université Paris 7 Pascale Senellart Jacqueline Bloch Cristiano Ciuti Carlo Sirtori