Single-photon nonlinear optics with Kerr-type nanostructured materials

We employ a quantum theory of the nonlinear optical response from an actual solid-state material possessing an intrinsic bulk contribution to the third-order nonlinear susceptibility (Kerr-type nonlinearity), which can be arbitrarily nanostructured to achieve diffraction-limited electromagnetic field confinement. By calculating the zero-time delay second-order correlation of the cavity field, we set the conditions for using semiconductor or insulating materials with near-infrared energy gaps as efficient means to obtain single-photon nonlinear behavior in prospective solid-state integrated devices, alternative to ideal sources of quantum radiation such as, e.g., single two-level emitters.Comment: 5 pages, three figure

Unconventional photon blockade in doubly resonant microcavities with second-order nonlinearity

It is shown that non-centrosymmetric materials with bulk second-order nonlinear susceptibility can be used to generate strongly antibunched radiation at an arbitrary wavelength, solely determined by the resonant behavior of suitably engineered coupled microcavities. The proposed scheme exploits the unconventional photon blockade of a coherent driving field at the input of a coupled cavity system, where one of the two cavities is engineered to resonate at both fundamental and second harmonic frequencies, respectively. Remarkably, the unconventional blockade mechanism occurs with reasonably low quality factors at both harmonics, and does not require a sharp doubly-resonant condition for the second cavity, thus proving its feasibility with current semiconductor technology

Topological aspects in the photonic crystal analog of single-particle transport in quantum Hall systems

We present a perturbative approach to derive the semiclassical equations of motion for the two-dimensional electron dynamics under the simultaneous presence of static electric and magnetic fields, where the quantized Hall conductance is known to be directly related to the topological properties of translationally invariant magnetic Bloch bands. In close analogy to this approach, we develop a perturbative theory of two-dimensional photonic transport in gyrotropic photonic crystals to mimic the physics of quantum Hall systems. We show that a suitable permittivity grading of a gyrotropic photonic crystal is able to simulate the simultaneous presence of analog electric and magnetic field forces for photons, and we rigorously derive the topology-related term in the equation for the electromagnetic energy velocity that is formally equivalent to the electronic case. A possible experimental configuration is proposed to observe a bulk photonic analog to the quantum Hall physics in graded gyromagnetic photonic crystals.Comment: to be published in Phys Rev

Visible quantum plasmonics from metallic nanodimers

We report theoretical evidence that bulk nonlinear materials weakly interacting with highly localized plasmonic modes in ultra-sub-wavelength metallic nanostructures can lead to nonlinear effects at the single plasmon level in the visible range. In particular, the two-plasmon interaction energy in such systems is numerically estimated to be comparable with the typical plasmon linewidths. Localized surface plasmons are thus predicted to exhibit a purely nonclassical behavior, which can be clearly identified by a sub-Poissonian second-order correlation in the signal scattered from the quantized plasmonic field under coherent electromagnetic excitation. We explicitly show that systems sensitive to single-plasmon scattering can be experimentally realized by combining electromagnetic confinement in the interstitial region of gold nanodimers with local infiltration or deposition of ordinary nonlinear materials. We also propose configurations that could allow to realistically detect such an effect with state-of-the-art technology, overcoming the limitations imposed by the short plasmonic lifetime

Optimal efficiency of the Q-cycle mechanism around physiological temperatures from an open quantum systems approach

The Q-cycle mechanism entering the electron and proton transport chain in oxygenic photosynthesis is an example of how biological processes can be efficiently investigated with elementary microscopic models. Here we address the problem of energy transport across the cellular membrane from an open quantum system theoretical perspective. We model the cytochrome $b_6f$ protein complex under cyclic electron flow conditions starting from a simplified kinetic model, which is hereby revisited in terms of a quantum master equation formulation and spin-boson Hamiltonian treatment. We apply this model to theoretically demonstrate an optimal thermodynamic efficiency of the Q-cycle around ambient and physiologically relevant temperature conditions. Furthermore, we determine the quantum yield of this complex biochemical process after setting the electrochemical potentials to values well established in the literature. The present work suggests that the theory of quantum open systems can successfully push forward our theoretical understanding of complex biological systems working close to the quantum/classical boundary.Comment: 13 pages, 6 figures. Pre-submission manuscript, see Journal Reference for the final versio

Analog Hawking radiation from an acoustic black hole in a flowing polariton superfluid

We theoretically study Hawking radiation processes from an analog acoustic black hole in a flowing superfluid of exciton-polaritons in a one-dimensional semiconductor microcavity. Polaritons are coherently injected into the microcavity by a laser pump with a suitably tailored spot profile. An event horizon with a large analog surface gravity is created by inserting a defect in the polariton flow along the cavity plane. Experimentally observable signatures of the analog Hawking radiation are identified in the scattering of phonon wavepackets off the horizon, as well as in the spatial correlation pattern of quantum fluctuations of the polariton density. The potential of these table-top optical systems as analog models of gravitational physics is quantitatively confirmed by numerical calculations using realistic parameters for state-of-the-art devices

Single-photon blockade in doubly resonant nanocavities with second-order nonlinearity

We propose the use of nanostructured photonic nanocavities made of chi((2)) nonlinear materials as prospective passive devices to generate strongly sub-Poissonian light via single-photon blockade of an input coherent field. The simplest scheme is based on the requirement that the nanocavity be doubly resonant, i.e., possess cavity modes with good spatial overlap at both the fundamental and second-harmonic frequencies. We discuss the feasibility of this scheme with state-of-the art nanofabrication technology and the possibility to use it as a passive single-photon source on demand

Cooperativity of a few quantum emitters in a single-mode cavity

We theoretically investigate the emission properties of a single-mode cavity coupled to a mesoscopic number of incoherently pumped quantum emitters. We propose an operational measure for the medium cooperativity, valid both in the bad and in the good cavity regimes. We show that the opposite regimes of subradiance and superradiance correspond to negative and positive cooperativity, respectively. The lasing regime is shown to be characterized by nonnegative cooperativity. In the bad cavity regime we show that the cooperativity defines the transitions from subradiance to superradiance. In the good cavity regime it helps to define the lasing threshold, also providing distinguishable signatures indicating the lasing regime. Increasing the quality of the cavity mode induces a crossover from the solely superradiant to the lasing regime. Furthermore, we verify that lasing is manifested in a wide range of positive cooperative behavior, showing that stimulated emission and superradiance can coexist. The robustness of the cooperativity is studied with respect to experimental imperfections, such as inhomogeneous broadening and pure dephasing

The quantum optical Josephson interferometer

The interplay between coherent tunnel coupling and on-site interactions in dissipation-free bosonic systems has lead to many spectacular observations, ranging from the demonstration of number-phase uncertainty relation to quantum phase transitions. To explore the effect of dissipation and coherent drive on tunnel coupled interacting bosonic systems, we propose a device that is the quantum optical analog of a Josephson interferometer. It consists of two coherently driven linear optical cavities connected via a central cavity with a single-photon nonlinearity. The Josephson-like oscillations in the light emitted from the central cavity as a function of the phase difference between two pumping fields can be suppressed by increasing the strength of the nonlinear coupling. Remarkably, we find that in the limit of ultra-strong interactions in the center-cavity, the coupled system maps on to an effective Jaynes-Cummings system with a nonlinearity determined by the tunnel coupling strength. In the limit of a single nonlinear cavity coupled to two linear waveguides, the degree of photon antibunching from the nonlinear cavity provides an excellent measure of the transition to the nonlinear regime where Josephson oscillations are suppressed.Comment: 9 pages, 7 figure

The quantum optical Josephson interferometer

The interplay between coherent tunnel coupling and on-site interactions in dissipation-free bosonic systems has lead to many spectacular observations, ranging from the demonstration of number-phase uncertainty relation to quantum phase transitions. To explore the effect of dissipation and coherent drive on tunnel coupled interacting bosonic systems, we propose a device that is the quantum optical analog of a Josephson interferometer. It consists of two coherently driven linear optical cavities connected via a central cavity with a single-photon nonlinearity. The Josephson-like oscillations in the light emitted from the central cavity as a function of the phase difference between two pumping fields can be suppressed by increasing the strength of the nonlinear coupling. Remarkably, we find that in the limit of ultra-strong interactions in the center-cavity, the coupled system maps on to an effective Jaynes-Cummings system with a nonlinearity determined by the tunnel coupling strength. In the limit of a single nonlinear cavity coupled to two linear waveguides, the degree of photon antibunching from the nonlinear cavity provides an excellent measure of the transition to the nonlinear regime where Josephson oscillations are suppressed.Comment: 9 pages, 7 figure