Condensed matter systems are potential candidates to realize the integration of quantum information circuits. Surface phonon polariton (SPhP) is a special propagation mode in condensed matter systems. We present an investigation on the entanglement of SPhP modes. The entangled pairs are generated from entangled photons injected to the system. Quantum performances of entangled SPhPs are investigated by using the interaction Hamiltonian and the perturbation theory. The wave mechanics approach is taken to describe the coupling process as a comparison. Finally, the correlation of system is examined. A whole set of descriptions of SPhP entanglement thus are presented.
Condensed matter systems are potential candidates to realize the integration of quantum information circuits. Surface phonon polariton (SPhP) is a special propagation mode in condensed matter systems. We present an investigation on the entanglement of SPhP modes. The entangled pairs are generated from entangled photons injected to the system. Quantum performances of entangled SPhPs are investigated by using the interaction Hamiltonian and the perturbation theory. The wave mechanics approach is taken to describe the coupling process as a comparison. Finally, the correlation of system is examined. A whole set of descriptions of SPhP entanglement thus are presented.
As a result of study on surface acoustic waves (SAWs), we propose protocols for generating the quantum entanglement on phonons. In the protocol of phonon–photon entanglement generation, the hybrid system is composed of a surface acoustic wave resonator (SAWR), a superconducting resonator (SR) and a nitrogen-vacancy-center ensemble (NVE). For the generation of three phonon modes entanglement, the SAWRs are coupled to the corresponding NVEs, while the NVEs interact with the same SR. Both protocols exploit the resonant interaction and the dispersive coupling. By considering the decoherence of the corresponding systems, the fidelities of the phonon–photon entanglement and three phonon modes entanglement reach 99.35% and 91.01%, respectively. Generalizing the approaches, we also present the protocol of multiple phonon modes entanglement.
Attempting to implement quantum information related applications utilizing atoms and photons, as they naturally form quantum systems supporting superposition states, hybrid quantum plasmonic systems emerged in the past as a platform to study and engineer light-matter interaction. This platform combines the unrivaled electromagnetic field localization of surface plasmon polaritons, boosting the light-matter coupling rate, with the tremendous integration potential of truly nanoscale structures, and both the significant emission rates of nanoantennas and photonic transmission velocities. In this work, a classical description of surface plasmon polaritons is combined with a light-matter interaction model based on a cavity quantum electrodynamical formalism. The resulting composite semi-classical method, introduced and described in this thesis, provides efficient and versatile means to simulate the dynamical behavior of radiative atomic transitions coupled to plasmonic cavity modes in the weak incoherent coupling regime. Both the emission into the far field and various dissipation mechanisms are included by expanding the model to an open quantum system. The variety of light-matter interaction applications that can be modeled with the outlined method is indicated by the four different exemplary scenarios detailed in the application chapter of this thesis. The classical description of localized surface plasmon polaritons is benchmarked by reproducing the experimental measurements of the molecular fluorescence manipulation through optical nanoantennas in a collaborative effort with experimental partners. Furthermore, in the weak light-matter coupling regime, the potential of achieving a higher nanoantenna functionality and simultaneously realizing more elaborate quantum dynamics is revealed by the three remaining applications. Each pivotally involving a bimodal nanoantenna and demonstrating different quantum optical phenomena, the implementation of cavity radiation mode conversion, non-classical cavity emission statistics, and non-classical cavity emission properties is shown and described in the application chapter.
Surface plasmon polaritons (SPPs) are collective excitations of free electrons propagating along a metal-dielectric interface. Although some basic quantum properties of SPPs, such as the preservation of entanglement, the wave-particle duality of a single plasmon, the quantum interference of two plasmons, and the verification of entanglement generation, have been shown, more advanced quantum information protocols have yet to be demonstrated with SPPs. Here, we experimentally realize quantum state teleportation between single photons and SPPs. To achieve this, we use polarization-entangled photon pairs, coherent photon-plasmon-photon conversion on a metallic subwavelength hole array, complete Bell-state measurements and an active feed-forward technique. The results of both quantum state and quantum process tomography confirm the quantum nature of the SPP mediated teleportation. An average state fidelity of [Formula: see text] and a process fidelity of [Formula: see text], which are well above the classical limit, are achieved. Our work shows that SPPs may be useful for realizing complex quantum protocols in a photonic-plasmonic hybrid quantum network.
Polaritons are quasi-particles originating from the coupling of light with matter and that demonstrated quantum phenomena at the many-particle mesoscopic level, such as BEC and superuidity. A highly sought and long-time missing feature of polaritons is a genuine quantum manifestation of their dynamics at the single-particle level. Although they are conceptually perceived as entangled states and theoretical proposals abound for an explicit manifestation of their single-particle properties, so far their behaviour remained fully accountable for by classical and mean-field theories. In this Article, we report the first experimental demonstration of a genuinely-quantum manifestation of microcavity polaritons, by swapping the entanglement between a polariton and an external photon from a photon pair generated by parametric down-conversion. Moreover we demonstrate how interactions manifest at a single polariton level by perturbing the entangled state with a rarefied polariton condensate. Our results open the page of quantum polaritonics and implement the first application of quantum spectroscopy.
The ultrastrong coupling between the elementary excitations of matter and microcavity modes is studied in a fully analytical quantum-mechanical theoretical framework. The elementary excitation could be phonons, excitons, plasmons, etc. From the diagonalization of the Hamiltonian, we obtain the ground state of the polariton Hamiltonian. The ground state belongs to the Gaussian class. Using the Gaussian property, we calculate the quantum entanglement in the ground state. We use two different measures for quantum entanglement---entanglement entropy and the logarithmic negativity parameter---and obtain rather simple analytical expressions for the entanglement measures. Our findings show that the amount of quantum entanglement in the ground state is quite significant in the ultrastrong-coupling regime. It can be obtained from the measurement of the polariton frequencies.
We develop a microscopic quantum theory of surface plasmon polaritons valid for arbitrary metal-dielectric geometries. Our framework is based on the Power-Zienau-Woolley representation of quantum electrodynamics, which provides an optimal separation between electronic and photonic degrees of freedom and is therefore particularly well suited for constructing quantum descriptions of polaritonic excitations in strongly dispersive media. Within this formulation, the fundamental electronic oscillator is identified as the bulk plasmon mode, which is nonperturbatively coupled to the radiative continuum of free photon modes. This coupling induces a geometry-dependent renormalization of the bulk plasma frequency, giving rise to confined plasmonic resonances. As specific applications, we recover the localized surface plasmon modes of metallic nanoparticles, including radiative frequency shifts and decay, as well as the exact dispersion relation of propagating surface plasmon polaritons at planar interfaces. Our quantum treatment further reveals that light-matter interactions at metal-dielectric interfaces are inherently in the ultrastrong coupling regime. As a result, in the quasistatic limit, the system exhibits unconventional ground-state quantum fluctuations that can be controlled through the refractive index. These results open new intriguing perspectives in the field of quantum plasmonics.