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D Tanese,
H Flayac,
D Solnyshkov,
A Amo,
A Lemaître,
E Galopin,
R Braive, P Senellart,
I Sagnes,
G Malpuech,
J Bloch
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ABSTRACT: Manipulation of nonlinear waves in artificial periodic structures leads to spectacular spatial features, such as generation of gap solitons or onset of the Mott insulator phase transition. Cavity exciton-polaritons are strongly interacting quasiparticles offering large possibilities for potential optical technologies. Here we report their condensation in a one-dimensional microcavity with a periodic modulation. The resulting mini-band structure dramatically influences the condensation process. Contrary to non-modulated cavities, where condensates expand, here, we observe spontaneous condensation in localized gap soliton states. Depending on excitation conditions, we access different dynamical regimes: we demonstrate the formation of gap solitons either moving along the ridge or bound to the potential created by the reservoir of uncondensed excitons. We also find Josephson oscillations of gap solitons triggered between the two sides of the reservoir. This system is foreseen as a building block for polaritonic circuits, where propagation and localization are optically controlled and reconfigurable.
Nature Communications 04/2013; 4:1749. · 7.40 Impact Factor
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ABSTRACT: We demonstrate unambiguous entangling operation of a photonic quantum-logic
gate driven by an ultrabright solid-state single-photon source.
Indistinguishable single photons emitted by a single semiconductor quantum dot
in a micropillar optical cavity are used as target and control qubits. For a
source brightness of 0.56 collected photons-per-pulse, the measured truth table
has an overlap with the ideal case of 68.4%, increasing to 73.0% for a source
brightness of 0.17 photons- per-pulse. The gate is entangling: at a source
brightness of 0.48, the Bell-state fidelity is above the entangling threshold
of 50%, and reaches 71.0% for a source brightness of 0.15.
03/2013;
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ABSTRACT: Bright sources of indistinguishable single photons are strongly needed for the scalability of quantum information processing. Semiconductor quantum dots are promising systems to build such sources. Several works demonstrated emission of indistinguishable photons while others proposed various approaches to efficiently collect them. Here we combine both properties and report on the fabrication of ultrabright sources of indistinguishable single photons, thanks to deterministic positioning of single quantum dots in well-designed pillar cavities. Brightness as high as 0.79±0.08 collected photon per pulse is demonstrated. The indistinguishability of the photons is investigated as a function of the source brightness and the excitation conditions. We show that a two-laser excitation scheme allows reducing the fluctuations of the quantum dot electrostatic environment under high pumping conditions. With this method, we obtain 82±10% indistinguishability for a brightness as large as 0.65±0.06 collected photon per pulse.
Nature Communications 02/2013; 4:1425. · 7.40 Impact Factor
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ABSTRACT: It has been proposed that valence-band holes can form robust spin qubits1, 2, 3, 4 owing to their weaker hyperfine coupling compared with electrons5, 6. However, it was demonstrated recently7, 8, 9, 10, 11 that the hole hyperfine interaction is not negligible, although a consistent picture of the mechanism controlling its magnitude is still lacking. Here we address this problem by measuring the hole hyperfine constant independently for each chemical element in InGaAs/GaAs, InP/GaInP and GaAs/AlGaAs quantum dots. Contrary to existing models10, 11 we find that the hole hyperfine constant has opposite signs for cations and anions and ranges from −15% to +15% relative to that for electrons. We attribute such changes to the competing positive contributions of p-symmetry atomic orbitals and the negative contributions of d-orbitals. These findings yield information on the orbital composition of the valence band12 and enable a fundamentally new approach for verification of computed Bloch wavefunctions in semiconductor nanostructures13. Furthermore, we show that the contribution of cationic d-orbitals leads to a new mechanism of hole spin decoherence.
Nature Physics 02/2013; 9(2):74. · 18.97 Impact Factor
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E Wertz,
A Amo,
D D Solnyshkov,
L Ferrier,
T C H Liew,
D Sanvitto, P Senellart,
I Sagnes,
A Lemaître,
A V Kavokin,
G Malpuech,
J Bloch
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ABSTRACT: The dynamics of propagating polariton condensates in one-dimensional microcavities is investigated through time resolved experiments. We find a strong increase in the condensate intensity when it travels through the nonresonantly excited area. This amplification is shown to come from bosonic stimulated relaxation of reservoir excitons into the polariton condensate, allowing for the repopulation of the condensate through nonresonant pumping. Thus, we experimentally demonstrate a polariton amplifier with a large band width, opening the way towards the transport of polaritons with high densities over macroscopic distances.
Physical Review Letters 11/2012; 109(21):216404. · 7.37 Impact Factor
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ABSTRACT: Giant optical nonlinearity is observed under both continuous wave and pulsed excitation in a deterministically coupled quantum dot-micropillar system, in a pronounced strong-coupling regime. Using absolute reflectivity measurements we determine the critical intracavity photon number as well as the input and output coupling efficiencies of the device. Thanks to a near-unity input-coupling efficiency, we demonstrate a record nonlinearity threshold of only 8 incident photons per pulse. The output-coupling efficiency is found to strongly influence this nonlinearity threshold. We show how the fundamental limit of single-photon nonlinearity can be attained in realistic devices, which would provide an effective interaction between two coincident single-photons.
Physical Review Letters 10/2012; 109(16):166806. · 7.37 Impact Factor
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C. Belacel,
B. Habert,
F. Bigourdan,
F. Marquier,
J. -P. Hugonin,
S. Michaelis de Vasconcellos,
X. Lafosse,
L. Coolen,
C. Schwob,
C. Javaux,
B. Dubertret,
J. -J. Greffet, P. Senellart,
A. Maitre
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ABSTRACT: We experimentally demonstrate the control of the spontaneous emission rate
and the radiation pattern of colloidal quantum dots deterministically
positioned in a plasmonic patch antenna. The antenna consists of a thin gold
microdisk 30 nm above a thick gold layer. The emitters are shown to radiate
through the entire patch antenna in a highly directional and vertical radiation
pattern. Strong acceleration of spontaneous emission is observed, depending of
the antenna size. Considering the double dipole structure of the emitters, this
corresponds to a Purcell factor up to 80 for dipoles perpendicular to the disk.
09/2012;
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D Tanese,
D D Solnyshkov,
A Amo,
L Ferrier,
E Bernet-Rollande,
E Wertz,
I Sagnes,
A Lemaître, P Senellart,
G Malpuech,
J Bloch
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ABSTRACT: We investigate the effect of disorder on the propagation of one-dimensional polariton condensates in semiconductor microcavities. We observe a strong suppression of the backscattering produced by the imperfections of the structure when increasing the condensate density. This suppression occurs in the supersonic regime and is simultaneous to the onset of parametric instabilities which enable the "hopping" of the condensate through the disorder. Our results evidence a new mechanism for the strong scattering reduction of polaritons at high speeds.
Physical Review Letters 01/2012; 108(3):036405. · 7.37 Impact Factor
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ABSTRACT: We demonstrate strong confinement of the optical field by depositing a micron sized metallic disk on a planar distributed Bragg reflector. Confined Tamm plasmon modes are evidenced both experimentally and theoretically, with a lateral confinement limited to the disk area and strong coupling to TE polarized fields. Single quantum dots controllably coupled to these modes are shown to experience acceleration of their spontaneous emission when spectrally resonant with the mode. For quantum dots spectrally detuned from the confined Tamm plasmon mode, an inhibition of spontaneous emission by a factor 40±4 is observed, a record value in the optical domain.
Physical Review Letters 12/2011; 107(24):247402. · 7.37 Impact Factor
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ABSTRACT: We report on an experimental and numerical study of the spatial and spectral properties of the optical modes in coupled pillar microcavities. Highly efficient photon blockade or bright sources of entangled photon pairs can be implemented by coupling a single quantum emitter to coupled cavities. Parameters for optimal coupling with a single quantum emitter are identified. Polarization properties, which are critical for both applications, are finally discussed. We show that an extremely small polarization splitting is obtained for the first modes in a wide range of parameters.
Applied Physics Letters 09/2011; 99(10):101103-101103-3. · 3.84 Impact Factor
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ABSTRACT: Highly polarized nuclear spins within a semiconductor quantum dot induce effective magnetic (Overhauser) fields of up to several Tesla acting on the electron spin, or up to a few hundred mT for the hole spin. Recently this has been recognized as a resource for intrinsic control of quantum-dot-based spin quantum bits. However, only static long-lived Overhauser fields could be used. Here we demonstrate fast redirection on the microsecond timescale of Overhauser fields on the order of 0.5 T experienced by a single electron spin in an optically pumped GaAs quantum dot. This has been achieved using coherent control of an ensemble of 10(5) optically polarized nuclear spins by sequences of short radiofrequency pulses. These results open the way to a new class of experiments using radiofrequency techniques to achieve highly correlated nuclear spins in quantum dots, such as adiabatic demagnetization in the rotating frame leading to sub-μK nuclear spin temperatures, rapid adiabatic passage, and spin squeezing.
Nature Material 08/2011; 10(11):844-8. · 32.84 Impact Factor
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ABSTRACT: We demonstrate strong confinement of the optical field by depositing a micron
sized metallic disk on a planar interferential mirror. Zero dimensional Tamm
plasmon modes are evidenced both experimentally and theoretically, with a
lateral confinement limited to the disk area and strong coupling to TE
polarized fields. Single quantum dots deterministically coupled to these modes
are shown to experience acceleration of their spontaneous emission when
spectrally resonant with the mode. For quantum dots spectrally detuned from the
confined Tamm Plasmon mode, an inhibition of spontaneous emission by a factor
40 is observed, a record value in the optical domain.
06/2011;
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[show abstract]
[hide abstract]
ABSTRACT: Highly polarized nuclear spins within a semiconductor quantum dot (QD) induce
effective magnetic (Overhauser) fields of up to several Tesla acting on the
electron spin or up to a few hundred mT for the hole spin. Recently this has
been recognized as a resource for intrinsic control of QD-based spin quantum
bits. However, only static long-lived Overhauser fields could be used. Here we
demonstrate fast redirection on the microsecond time-scale of Overhauser fields
of the order of 0.5 T experienced by a single electron spin in an optically
pumped GaAs quantum dot. This has been achieved using full coherent control of
an ensemble of 10^3-10^4 optically polarized nuclear spins by sequences of
short radio-frequency (rf) pulses. These results open the way to a new class of
experiments using rf techniques to achieve highly-correlated nuclear spins in
quantum dots, such as adiabatic demagnetization in the rotating frame leading
to sub-micro K nuclear spin temperatures, rapid adiabatic passage, and spin
squeezing.
02/2011;
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ABSTRACT: The exciton and biexciton lines of a single quantum dot are deterministically coupled to the optical modes of a photonic molecule. The resonance between the quantum dot emission lines and the molecule cavity modes is reached at 53 K. The device operates as a very bright source of entangled photon pairs, with an extraction efficiency of 40% for each photon of the pair. Our measurements show that the use of Purcell effect allows to quench the exciton spin relaxation during the radiative cascade, at 53 K and at high excitation power.
Applied Physics Letters 08/2010; 97(8):081104-081104-3. · 3.84 Impact Factor
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ABSTRACT: We report optically detected nuclear magnetic resonance (ODNMR) measurements
on small ensembles of nuclear spins in single GaAs quantum dots. Using ODNMR we
make direct measurements of the inhomogeneous Knight field from a photo-excited
electron which acts on the nuclei in the dot. The resulting shifts of the NMR
peak can be optically controlled by varying the electron occupancy and its spin
orientation, and lead to strongly asymmetric lineshapes at high optical
excitation. The all-optical control of the NMR lineshape will enable
position-selective control of small groups of nuclear spins in a dot. Our
calculations also show that the asymmetric NMR peak lineshapes can provide
information on the volume of the electron wave-function, and may be used for
measurements of non-uniform distributions of atoms in nano-structures.
02/2010;
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ABSTRACT: We observe spontaneously driven nonground state polariton condensation in GaAs pillar microcavities under nonresonant optical excitation. We identify a regime where the interplay of exciton-exciton and pair polariton scattering can lead to mode switching from nonground state to ground state polariton condensation. A simple kinematic model satisfactorily describes the observed mode switching as each of the above scattering mechanisms becomes prevalent at different carrier densities.
Physical Review B. 02/2010; 81:081307.
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ABSTRACT: The origin of the emission within the optical mode of a coupled quantum dot-micropillar system is investigated. Time-resolved photoluminescence is performed on a large number of deterministically coupled devices in a wide range of temperature and detuning. The emission within the cavity mode is found to exhibit the same dynamics as the spectrally closest quantum dot state. Our observations indicate that fast dephasing of the quantum dot state is responsible for the emission within the cavity mode. An explanation for recent photon correlation measurements reported on similar systems is proposed.
Physical Review Letters 08/2009; 103(2):027401. · 7.37 Impact Factor
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ABSTRACT: We observe spontaneously driven non-ground state polariton condensation in GaAs pillar microcavities under non-resonant optical excitation. We identify a regime where the interplay of exciton-exciton and pair polariton scattering can lead to mode switching from non-ground state to ground state polariton condensation. A simple kinematic model satisfactorily describes the observed mode switching as each of the above scattering mechanisms becomes prevalent at different carrier densities. Comment: 4 pages, 3 figures
07/2009;
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ABSTRACT: The origin of the emission within the optical mode of a coupled quantum dot-micropillar system is investigated. Time-resolved photoluminescence is performed on a large number of deterministically coupled devices in a wide range of temperature and detuning. The emission within the cavity mode is found to exhibit the same dynamics as the spectrally closest quantum dot state. Our observations indicate that fast dephasing of the quantum dot state is responsible for the emission within the cavity mode. An explanation for recent photon correlation measurements reported on similar systems is proposed. Comment: 4 pages, 4 figures
04/2009;
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ABSTRACT: Nuclear spin polarization dynamics are measured in optically pumped
individual GaAs/AlGaAs interface quantum dots by detecting the time-dependence
of the Overhauser shift in photoluminescence (PL) spectra. Long nuclear
polarization decay times of ~ 1 minute have been found indicating inefficient
nuclear spin diffusion from the GaAs dot into the surrounding AlGaAs matrix in
externally applied magnetic field. A spin diffusion coefficient two orders
lower than that previously found in bulk GaAs is deduced.
01/2009;
