We report observation of optical binding between two dielectric particles with dimensions less than the wavelength of the interacting light. The observed dependence of the separation of optically bound Rayleigh particles on the polarization of the trapping beam is in agreement with earlier theoretical predictions.

Using two optical pulses of different frequencies, we demonstrate entanglement and disentanglement of the electronic states in Stranski-Krastanov quantum dots. Resonant two-photon excitation of the biexciton creates an entangled Bell-like state. The second pulse, being resonant to the excitonbiexciton transition, stimulates the emission from the biexciton and fully disentangles the two-bit system. By setting the polarization of the stimulation pulse, we control the recombination path of the biexciton and, by this, the state of the photons emitted in the decay cascade.PACS numbers: 42.50. Md, 78.67.Hc, 78.55.Et Entangled states and their manipulation play an important role in quantum information processing [1]. A state of a pair of quantum systems is said to be entangled if it cannot be factored into the states of the individual subsystems. When aiming at practical devices, implementations in solid state are of particular interest. Here, a critical issue is decoherence that destroys the non-classical quantum correlations.Semiconductor quantum dots (QDs) with electronic excitations localized on a nanometer length scale have recently attracted much attention as building blocks for quantum logic [2,3]. The two-exciton subspace of a QD is spanned by the ground-state |g (no exciton), the singleexciton states, and the biexciton state |b . The optically active exciton is split by anisotropy in two linearly crosspolarized components |x and |y [4]. Thus, identifying |00 = |g , |10 = |x , |01 = |y , and |11 = |b , a twobit system is built. The optical couplings between those states form the V − Λ transition scheme of Fig. 1a, where the exciton-biexciton resonances are low-energy shifted from that of the single excitons by the exciton-exciton interaction energy ∆E XX in the biexciton.Coherent optical coupling of the ground-state and the biexciton creates an entangled state of the type a 00 |00 + a 11 |11 [5,6]. A Bell state of maximum entanglement is achieved if |a ii | = 1 √ 2

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