arXiv subjects

Emiliano Cancellieri

Publications and source records attributed to Emiliano Cancellieri.

12 recordsLinked to original sources

arXiv2019

Conservation of Quantum Correlations in Multimode Systems with $U(1)$ Symmetry

We present a theoretical investigation of the properties of quantum correlation functions in a dissipative multimode system. We define a total mth order equal-time correlation function, summed over all modes, which is shown to be conserved if the Hamiltonian possesses U(1) symmetry, provided any dissipation processes are linear in the system operators. As examples, we demonstrate this conservation using numerical simulations of a coupled cavity system and the Jaynes-Cummings model.

quant-ph↗

arXiv2018

Topological dynamics and excitations in lasers and condensates with saturable gain or loss

We classify symmetry-protected and symmetry-breaking dynamical solutions for nonlinear saturable bosonic systems that display a non-hermitian charge-conjugation symmetry, as realized in a series of recent groundbreaking experiments with lasers and exciton polaritons. In particular, we show that these systems support stable symmetry-protected modes that mirror the concept of zero-modes in topological quantum systems, as well as symmetry-protected power-oscillations with no counterpart in the linear case. In analogy to topological phases in linear systems, the number and nature of symmetry-protected solutions can change. The spectral degeneracies signalling phase transitions in linear counterparts extend to bifurcations in the nonlinear context. As bifurcations relate to qualitative changes in the linear stability against changes of the initial conditions, the symmetry-protected solutions and phase transitions can also be characterized by topological excitations, which set them apart from symmetry-breaking solutions. The stipulated symmetry appears naturally when one introduces nonlinear gain or loss into spectrally symmetric bosonic systems, as we illustrate for one-dimensional topological laser arrays with saturable gain and two-dimensional flat-band polariton condensates with density-dependent loss.

cond-mat.mes-hall↗

arXiv2018

Quantum optics of nonlinear systems in cascade

In this letter, we investigate the quantum optical properties of driven-dissipative nonlinear systems in a cascade configuration. We show that pumping a nonlinear system with a state having a noncoherent statistics, can improve the antibunching of the output state and, consequently, the nonclassicality of the whole system. Furthermore, we show that is possible to generate entanglement through dissipative coupling. These results applies to a broad category of physical systems with a Kerr-like non-linearity, from Rydberg atoms to exciton polaritons in microcavities.

quant-ph↗

arXiv2018

Coherent merging of counter-propagating exciton-polariton superfluids

We report the formation of a macroscopic coherent state emerging from colliding polariton fluids. Four lasers with random relative phases, arranged in a square, pump resonantly a planar microcavity, creating four coherent polariton fluids propagating toward each other. When the density (interactions) increases, the four fluids synchronise and the topological excitations (vortex or soliton) disappear to form a single superfluid.

cond-mat.quant-gas↗

arXiv2016

Full Stark Control of Polariton States on a Spin-Orbit Hypersphere

The orbital angular momentum and the polarisation of light are physical quantities widely investigated for classical and quantum information processing. In this work we propose to take advantage of strong light-matter coupling, circular-symmetric confinement, and transverse-electric transverse-magnetic splitting to exploit states where these two degrees of freedom are combined. To this end we develop a model based on a spin-orbit Poincaré hypersphere. Then we consider the example of semiconductor polariton systems and demonstrate full ultrafast Stark control of spin-orbit states. Moreover, by controlling states on three different spin-orbit spheres and switching from one sphere to another we demonstrate the control of different logic bits within one single physical system.

cond-mat.mes-hall↗

arXiv2016

Injection of orbital angular momentum and storage of quantized vortices in polariton superfluids

We report the experimental investigation and theoretical modeling of a rotating polariton superfluid relying on an innovative method for the injection of angular momentum. This novel, multi-pump injection method uses four coherent lasers arranged in a square, resonantly creating four polariton populations propagating inwards. The control available over the direction of propagation of the superflows allows injecting a controllable non-quantized amount of optical angular momentum. When the density at the center is low enough to neglect polariton-polariton interactions, optical singularities, associated to an interference pattern, are visible in the phase. In the superfluid regime resulting from the strong nonlinear polariton-polariton interaction, the interference pattern disappears and only vortices with the same sign are persisting in the system. Remarkably the number of vortices inside the superfluid region can be controlled by controlling the angular momentum injected by the pumps.

cond-mat.quant-gas↗

arXiv2015

Logic Gates with Bright Dissipative Polariton Solitons in Bragg-Cavity Systems

Optical solitons are an ideal platform for the implementation of communication lines, since they can be packed extremely close one to another without risking partial loss of the encoded information due to their interaction. On the other hand, soliton-soliton interactions are needed to implement computations and achieve all-optical information processing. Here we study how bright dissipative polariton solitons interact and exploit their interaction to implement AND and OR gates with state of the art technology. Moreover, we show that soliton-soliton interaction can be used to determine the sign of α2, the parameter describing the interaction between polaritons with opposite spin.

cond-mat.other↗

arXiv2015

Merging of vortices and antivortices in polariton superfluids

Quantised vortices are remarkable manifestations on a macroscopic scale of the coherent nature of quantum fluids, and the study of their properties is of fundamental importance for the understanding of this peculiar state of matter. Cavity-polaritons, due to their double light-matter nature, offer a unique controllable environment to investigate these properties. In this work we theoretically investigate the possibility to deterministically achieve the annihilation of a vortex with an antivortex through the increase of the polariton density in the region surrounding the vortices. Moreover we demonstrate that by means of this mechanism an array of vortex-antivortex pairs can be completely washed out.

cond-mat.other↗

arXiv2014

Interaction-Shaped Vortex-Antivortex Lattices in Polariton Fluids

Topological defects such as quantized vortices are one of the most striking manifestations of the superfluid nature of Bose-Einstein condensates and typical examples of quantum mechanical phenomena on a macroscopic scale. Here we demonstrate the formation of a lattice of vortex-antivortex pairs and study, for the first time, its properties in the non-linear regime at high polarion-density where polariton-polariton interactions dominate the behaviour of the system. In this work first we demonstrate that the array of vortex-antivortex pairs can be generated in a controllable way in terms of size of the array and in terms of size and shape of it fundamental unit cell. Then we demonstrate that polariton-polariton repulsion can strongly deform the lattice unit cell and determine the pattern distribution of the vortex-antivortex pairs, reaching a completely new behaviour with respect to geometrically generated vortex lattices whose shape is determined only by the geometry of the system.

cond-mat.quant-gas↗

arXiv2014

Ultra-Fast Stark-Induced Control of Polaritonic States

A laser pulse, several meV red-detuned from the excitonic line of a quantum well, has been shown to induce an almost instantaneous and rigid shift of the lower and upper polariton branches. Here we demonstrate that through this shift, ultra-fast all-optical control of the polariton population in a semiconductor microcavity should be achievable. In the proposed setup a Stark field is used to bring the lower polariton branch in or out of resonance with a quasi-resonant continuous-wave laser, thereby favoring or inhibiting the injection of polaritons into the cavity. Moreover we show that this technique allows for the implementation of optical switches with extremely high repetition rates.

cond-mat.mes-hall↗

arXiv2013

All-optical polariton transistor

While optical technology provides the best solution for the transmission of information, optical logics still calls for qualitative new concepts to be explored. Exciton-polaritons are composite particles, resulting from the strong coupling between excitons and photons, which have recently demonstrated exceptional properties like huge non-linearities, long range coherence and suppression of scattering. Here we demonstrate a switching scheme for polaritons moving in the plane of a microcavity which satisfy all the requirements for an all-optical transistor. Under resonant excitation, the power threshold for the nonlinear increase of the polariton density is varied by a weak control beam, obtaining up to 19 times amplification with switching energies in the range of attojoule per square micron. Polariton propagation in the plane of the microcavity is then used to control the switching of a second, spatially separated transistor, opening the way to the implementation of polariton integrated circuits.

cond-mat.mes-hall↗

arXiv2007

Effect of the Pauli Exclusion Principle in the Many-Electron Wigner Function

An analysis of the Wigner function for identical particles is presented. Four situations have been considered. i) A scattering process between two indistinguishable electrons described by a minimum uncertainty wave packets showing the exchange and correlation hole in Wigner phase space. ii) An equilibrium ensemble of N electrons in a one-dimensional box and in a one-dimensional harmonic potential showing that the reduced single particle Wigner function as a function of the energy defined in the Wigner phase-space tends to a Fermi distribution. iii) The reduced one-particle transport-equation for the Wigner function in the case of interacting electrons showing the need for the two-particle reduced Wigner function within the BBGKY hierarchy scheme. iv) The electron-phonon interaction in the two-particle case showing co-participation of two electrons in the interaction with the phonon bath.

cond-mat.other↗