Özgür E. Müstecaplıoğlu

Electromagnetically induced left-handedness in a dense gas of three-level atoms

We discuss how a three-level system can be used to change the frequency-dependent magnetic permeability of an atomic gas to be significantly different from 1. We derive the conditions for such a scheme to be successful and briefly discuss the resulting macroscopic electrodynamics. We find that it may be possible to obtain left-handed electrodynamics for an atomic gas using three atomic levels.

Single-mode approximation in a spinor-1 atomic condensate

We investigate the validity conditions of the single-mode approximation (SMA) in a spinor-1 atomic condensate when effects due to residual magnetic fields are negligible. For atomic interactions of the ferromagnetic type, the SMA is shown to be exact, with a mode function different from what is commonly used. However, the quantitative deviation is small under current experimental conditions (for (87)Rb atoms). For antiferromagnetic interactions, we find that the SMA becomes invalid in general. The differences among the mean-field mode functions for the three spin components are shown to depend strongly on the system magnetization. Our results can be important for studies of beyond mean-field quantum correlations, such as fragmentation, spin squeezing, and multipartite entanglement.

Indistinguishable photons from a single molecule.

We report the results of coincidence counting experiments at the output, of a Michelson interferometer using the zero-phonon-line emission of a single molecule at 1.4 K. Under continuous wave excitation, we observe the absence of coincidence counts as an indication of two-photon interference. This corresponds to the observation of Hong-Ou-Mandel correlations and proves the suitability of the zero-phonon-line emission of single molecules for applications in linear optics quantum computation.

Superradiant light scattering from trapped Bose-Einstein condensates

We propose an alternative formulation for atomic side mode dynamics from superradiant light scattering of trapped atoms. A detailed analysis of the recently observed superradiant light scattering from trapped Bose gases [S. Inouye et al., Science 285, 571 (1999)] is presented. We find that scattered light intensity can exhibit both oscillatory and exponential growth behaviors depending on densities, pump pulse characteristics, temperatures, and geometric shapes of trapped gas samples. The total photon scattering rate as well as the accompanying matter wave amplification depend explicitly on atom number fluctuations in the condensate. Our formulation allows for natural and transparent interpretations of subtle features in the experimental data, and provides numerical simulations in good agreement with most important aspects of the experimental observations.

Field-effect active plasmonics for ultracompact electro-optic switching

Merging of electronics and photonics at subwavelength dimensions could potentially allow development of ultracompact electro-optic modulators and active optical interconnects. Here, we introduce a field-effect active plasmonic modulator where the metallic ring serves as both a photonic resonator and a field electrode. By exploiting the simultaneous electronic and photonic functionalities of our plasmonic device, we show devices offering significantly improved modulation depths (as high as ∼10.85 dB) compared to active dielectric micro-ring resonators. Device concepts introduced in this work are applicable in realization of various integrated components and could play an important role in development of active plasmonic circuits.

Spin squeezing and entanglement in spinor condensates

We analyze quantum correlation properties of a spinor-1 (f=1) Bose Einstein condensate using the Gell-Mann realization of SU(3) symmetry. We show that previously discussed phenomena of condensate fragmentation and spin-mixing can be explained in terms of the hypercharge symmetry. The ground state of a spinor-1 condensate is found to be fragmented for ferromagnetic interactions. The notion of two bosonic mode squeezing is generalized to the two spin (U-V) squeezing within the SU(3) formalism. Spin squeezing in the isospin subspace (T) is found and numerically investigated. We also provide new results for the stationary states of spinor-1 condensates.

Superradiant Quantum Heat Engine.

Quantum physics revolutionized classical disciplines of mechanics, statistical physics, and electrodynamics. One branch of scientific knowledge however seems untouched: thermodynamics. Major motivation behind thermodynamics is to develop efficient heat engines. Technology has a trend to miniaturize engines, reaching to quantum regimes. Development of quantum heat engines (QHEs) requires emerging field of quantum thermodynamics. Studies of QHEs debate whether quantum coherence can be used as a resource. We explore an alternative where it can function as an effective catalyst. We propose a QHE which consists of a photon gas inside an optical cavity as the working fluid and quantum coherent atomic clusters as the fuel. Utilizing the superradiance, where a cluster can radiate quadratically faster than a single atom, we show that the work output becomes proportional to the square of the number of the atoms. In addition to practical value of cranking up QHE, our result is a fundamental difference of a quantum fuel from its classical counterpart.

Excitations of optically driven atomic condensate in a cavity: theory of photodetection measurements

Recent experiments have demonstrated an open system realization of the Dicke quantum phase transition in the motional degrees of freedom of an optically driven Bose–Einstein condensate in a cavity. Relevant collective excitations of this light–matter system are polaritonic in nature, allowing access to the quantum critical behavior of the Dicke model through light leaking out of the cavity. This opens the path to using photodetection-based quantum optical techniques to study the dynamics and excitations of this elementary quantum critical system. We first discuss the photon flux observed at the cavity face and find that it displays a different scaling law near criticality than that obtained from the mean-field theory for the equivalent closed system. Next, we study the second-order correlation measurements of photons leaking out of the cavity. Finally, we discuss a modulation technique that directly captures the softening of polaritonic excitations. Our analysis takes into account the effect of the finite size of the system, which may result in an effective symmetry-breaking term.

Spin squeezing, entanglement, and coherence in two driven, dissipative, nonlinear cavities coupled with single- and two-photon exchange

We investigate spin squeezing, quantum entanglement, and second-order coherence in two coupled, driven, dissipative, nonlinear cavities. We compare these quantum statistical properties for the cavities coupled with either single- or two-photon exchange. Solving the quantum optical master equation of the system numerically in the steady state, we calculate the zero-time delay second-order correlation function for the coherent, genuine two-mode entanglement parameters, an optimal spin squeezing inequality associated with particle entanglement, concurrence, quantum entropy, and logarithmic negativity. We identify regimes of distinct quantum statistical character depending on the relative strength of photon exchange and nonlinearity. Moreover, we examine the effects of weak and strong drives on these quantum statistical regimes.

Active control of focal length and beam deflection in a metallic nanoslit array lens with multiple sources

We propose an all-optical method to actively control the transmission of nanoslit arrays for scanning and lensing applications. We show that by utilizing two lateral control slits, the transmitted beam can be actively steered.