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Gor Nikoghosyan

Publications and source records attributed to Gor Nikoghosyan.

10 recordsLinked to original sources
arXiv2026

Polar optical scattering in ellipsoidal nanoclusters

The influence of the specific geometry of three-dimensional confinement on electron- vibrational coupling in InAs/GaAs nanoclusters shaped as highly oblate ellipsoids of revolution is considered. Optical phonon relaxation processes are analyzed taking into account the law of conservation of angular momentum projection and the spatial symmetry of the dimensional confinement. The conditions for the emission of chiral optical phonons carrying orbital angular momentum along the structure's growth axis are analyzed. Intraband relaxation transitions with the emission of LO phonons with zero angular momentum, with characteristic anisotropy of the emission direction, leading to nonmonotonic size dependences for the e-ph coupling coefficient, are considered.

cond-mat.mes-hall↗
arXiv2025

Quantum Aberrations: Entangling Photons with Zernike Polynomials

We introduce Zernike polynomials as a novel degree of freedom for encoding quantum information in the spatial structure of photons. Building on their orthogonality and completeness over the unit disc, we develop a framework for generating, manipulating, and detecting photons in Zernike modes, and propose methods for realizing single-photon and two-photon Zernike wave packets. We demonstrate analytically that two-photon states generated via spontaneous parametric down- conversion exhibit mode entanglement in the Zernike basis, with correlations arising from selection rules enforced by Clebsch-Gordan coefficients. Our results open a new pathway for structured spatial entanglement, complementary to schemes based on Laguerre-Gaussian or Hermite-Gaussian modes, and suggest practical experimental implementations based on holographic modulation and optical Fourier techniques.

quant-ph↗
arXiv2012

Generation of mesoscopic entangled states in a cavity coupled to an atomic ensemble

We propose a novel scheme for the efficient production of "NOON states" based on the resonant interaction of a pair of quantized cavity modes with an ensemble of atoms. We show that in the strong-coupling regime the adiabatic evolution of the system tends to a limiting state that describes mesoscopic entanglement between photons and atoms which can easily be converted to a purely photonic or atomic NOON state. We also demonstrate the remarkable property that the efficiency of this scheme increases exponentially with the cavity cooperativity factor, which gives efficient access to high number NOON states. The experimental feasibility of the scheme is discussed and its efficiency is demonstrated numerically.

quant-ph↗
arXiv2011

Dipolar Bose-Einstein condensate of Stationary-Light Dark-state Polaritons

We put forward and discuss in detail a scheme to achieve Bose-Einstein condensation of stationary-light dark-state polaritons with dipolar interaction. To this end we have introduced a diamond-like coupling scheme in a vapor of Rydberg atoms under the frozen gas approximation. To determine the system's dynamics we employ normal modes and identify the dark-state polariton corresponding to one of the modes. We show that in contrast to atomic dipolar ultra-cold vapors dark-state polariton Bose-Einstein condensates proposed here can be stable for a negative dipolar interaction constant.

quant-ph↗
arXiv2010

Photon-number selective group delay in cavity induced transparency

We show that the group velocity of a probe pulse in an ensemble of $Λ$-type atoms driven by a quantized cavity mode depends on the quantum state of the input probe pulse. In the strong-coupling regime of the atom-cavity system the probe group delay is photon number selective. This can be used to spatially separate the single photon from higher photon-number components of a few-photon probe pulse and thus to create a deterministic single-photon source.

quant-ph↗
arXiv2009

Frequency matching in light storage spectroscopy of atomic Raman transitions

We investigate the storage of light in an atomic sample with a lambda-type coupling scheme driven by optical fields at variable two-photon detuning. In the presence of electromagnetically induced transparency (EIT), light is stored and retrieved from the sample by dynamically varying the group velocity. It is found that for any two-photon detuning of the input light pulse within the EIT transparency window, the carrier frequency of the retrieved light pulse matches the two-photon resonance frequency with the atomic ground state transition and the control field. This effect which is not based on spectral filtering is investigated both theoretically and experimentally. It can be used for high-speed precision measurements of the two-photon resonance as employed e.g. in optical magnetometry.

physics.atom-ph↗
arXiv2009

Stationary light in cold atomic gases

We discuss stationary light created by a pair of counter-propagating control fields in Lambda-type atomic gases with electromagnetically induced transparency for the case of negligible Doppler broadening. In this case the secular approximation used in the discussion of stationary light in hot vapors is no longer valid. We discuss the quality of the effective light-trapping system and show that in contrast to previous claims it is finite even for vanishing ground-state dephasing. The dynamics of the photon loss is in general non exponential and can be faster or slower than in hot gases.

quant-ph↗
arXiv2009

Irreversible photon transfer in an ensemble of $Λ$-type atoms and photon diode

We show that a pair of quantized cavity modes interacting with a spectrally broadened ensemble of Lambda-type atoms is analogous to an ensemble of two level systems coupled to a bosonic reservoir. This provides the possibility for an irreversible photon transfer between photon modes. The density of states as well as the quantum state of the reservoir can be engineered allowing the observation of effects such as the quantum Zeno- and anti-Zeno effect, the destructive interference of decay channels and the decay in a squeezed vacuum. As a particular application we discuss a photon diode, i.e. a device which directs a single photon from anyone of two input ports to a common output port.

quant-ph↗
arXiv2004

Storage and perpendicular retrieving of two-dimensional pulses in electromagnetically induced transparency media

Propagation of two dimensional pulses in electromagnetically induced tranparency media in the case of perpendicular storing and retrieving pulses has been analyzed. It has been shown that propagation control of the pulses in optically thick media can be used for producing interchange between pulse time-shape and intensity profile distribution. A simple obvious analytical solution for the retrieved new field has been obtained.

quant-ph↗