arXiv subjects

Mikayel Khanbekyan

Publications and source records attributed to Mikayel Khanbekyan.

6 recordsLinked to original sources

arXiv2026

Pulsed single-photon magnetometry with a $Λ$-type three-level system: near-optimal frequency-resolved photon counting

We investigate pulsed single-photon magnetometry with a Zeeman-sensitive $Λ$-type three-level system driven by a classical control field. We derive the asymptotic output state and decompose its quantum Fisher information into photon-loss, spectral-intensity, and spectral-phase contributions. Environmental coupling reshapes the scattering response and can increase magnetic-field information. At critical coupling, real-frequency zeros of the scattering amplitude redistribute information toward measurable spectral intensity, allowing frequency-resolved photon counting to capture nearly all of the magnetic-field information encoded in the output state when the zeros lie within the pulse bandwidth. For long Gaussian pulses with a smooth, nonzero central-frequency scattering amplitude, the additional spectral-intensity contribution and residual spectral-phase information gap decrease as $T^{-2}$ or faster.

quant-ph↗

arXiv2026

Charging of a Quantum Battery by a Two-Photon Quantum Pulse

We investigate the charging of a harmonic-oscillator quantum battery by a propagating two-photon quantum pulse coupled through a two-level-system charger. Excitation-number conservation reduces the dynamics to a sequential response of the first and second excitation sectors, whose effective non-Hermitian generators exhibit two exceptional points separating overdamped, mixed, and underdamped regimes. We derive the exact full-charging amplitude and the response-matched two-photon temporal mode that achieves perfect charging in the ideal resonant single-channel model. For experimentally accessible Gaussian pulses, moderate temporal anticorrelation or a finite photon delay can enhance charging, whereas positive correlations generally suppress it. States with equal Schmidt number can nevertheless show different charging efficiencies, demonstrating that temporal-mode structure and response matching, rather than nonseparability alone, determine charging performance.

quant-ph↗

arXiv2026

Resonances in light scattering from nonequilibrium dipole pairs

We identify a fundamentally new class of resonances in light scattering from a pair of point-like electric dipoles. These resonances arise from multiple scattering response and correspond to poles of the two-particle Green function. The realization of exact resonances requires violation of the optical theorem, which holds in equilibrium systems but can be violated under nonequilibrium conditions, without violating causality. As a concrete example, we show that a pumped two-level atom can realize the required polarizability and access the exact resonance regime. Our results for one electric and one magnetic dipole show how resonances can amplify a weak magnetic response of a single dipole to the incident field. In equilibrium systems, only approximate resonances with finite amplification are possible. Using the Drude model for metallic nanoparticles, we show that while equilibrium resonances enhance the scattering, they never exceed the optimal single-dipole response.

physics.optics↗

arXiv2009

Cavity-assisted spontaneous emission of a single three-level atom as a single-photon source

Stimulated Raman interaction of a classically pumped single three-level $Λ$-type atom in a resonator cavity featuring both radiative and unwanted losses is studied. It is shown that in the regime of stimulated adiabatic Raman passage the excited outgoing wave packet of the cavity-assisted electromagnetic field can be prepared in a one-photon Fock state with high efficiency. In this regime, the spatio-temporal shape of the wave packet does not depend on the interaction shape of the pump field, provided that the interaction of the atom with the pump is time-delayed with respect to the interaction of the atom with the cavity-assisted field. Therefore, the scheme can be used to generate a sequence of identical radiation pulses each of almost one-photon Fock state. It is further shown that the spatio-temporal shape of the outgoing wave packet can be manipulated by controlling the time of interaction between the atom and the cavity-assisted electromagnetic field.

quant-ph↗

arXiv2003

Input-output relations at dispersing and absorbing planar multilayers for the quantized electromagnetic field containing evanescent components

By using the Green-function concept of quantization of the electromagnetic field in dispersing and absorbing media, the quantized field in the presence of a dispersing and absorbing dielectric multilayer plate is studied. Three-dimensional input-output relations are derived for both amplitude operators in the ${\bf k}$-space and the field operators in the coordinate space. The conditions are discussed, under which the input-output relations can be expressed in terms of bosonic operators. The theory applies to both (effectively) free fields and fields, created by active atomic sources inside and/or outside the plate, including also evanescent-field components.

quant-ph↗

arXiv2000

Generation of coherent superposition of Fock states in a cavity. Entanglement of atomic coherent states

A scheme for preparation of coherent superposition of Fock states of electromagnetic field is constructed. The superposition state is created inside the cavity via a strong interaction of a four-level atom with quantum field of the cavity and classic laser fields. We demonstrate the possibility to create desired arbitrary superposition of the cavity Fock states just by changing the relative delay of the fields. Then, as another application of our model, we study a means of creating entanglement of neutral four-level atoms using different sequences of interactions with the cavity and laser fields.

quant-ph↗