arXiv subjects

Maria Erukhimova

Publications and source records attributed to Maria Erukhimova.

12 recordsLinked to original sources

arXiv2023

Coulomb-induced synchronization of intersubband coherences in highly doped quantum wells and the formation of giant collective resonances

Many-body Coulomb interactions drastically modify the optical response of highly doped semiconductor quantum wells leading to a merger of all intersubband transition resonances into one sharp peak at the frequency substantially higher than all single-particle transition frequencies. Starting from standard density matrix equations for the gas of pairwise interacting fermions within Hartree-Fock approximation, we show that this effect is due to Coulomb-induced synchronization of the oscillations of coherences of all $N$ intersubband transitions and sharp collective increase in their coupling with an external optical field. In the high doping limit, the dynamics of light-matter interaction is described by the analytic theory of $N$ coupled oscillators which determines new collective normal modes of the system and predicts the frequency and strength of the blueshifted collective resonance.

cond-mat.mes-hall↗

arXiv2022

Dissipation-driven formation of entangled dark states in strongly-coupled inhomogeneous many-qubit systems in solid-state nanocavities

We study quantum dynamics of many-qubit systems strongly coupled to a quantized electromagnetic cavity field in the presence of decoherence and dissipation for both fermions and cavity photons, and taking into account the varying coupling strength of different qubits to the cavity field and the spread of their transition frequencies. Compact analytic solutions for time-dependent quantum state amplitudes and observables are derived for a broad class of open quantum systems in Lindblad approximation with the use of the stochastic Schroedinger equation approach. We show that depending on the initial quantum state preparation, an ensemble of qubits can evolve into a rich variety of many-qubit entangled states with destructive or constructive interference between the qubits. In particular, when only a small fraction of qubits is initially excited, the dissipation in a cavity will inevitably drive the system into robust dark states that are completely decoupled from the cavity and live much longer than the decay time of the cavity field. We also determine the conditions under which coherent coupling to the quantized cavity field overcomes the dephasing caused by a spread of transition frequencies in multi-qubit systems and leads to the formation of a decoupled dark state.

quant-ph↗

arXiv2022

The universal model of strong coupling at the nonlinear parametric resonance in open cavity-QED systems

Many molecular, quantum-dot, and optomechanical nanocavity-QED systems demonstrate strong nonlinear interactions between electrons, photons, and phonon (vibrational) modes. We show that such systems can be described by a universal model in the vicinity of the nonlinear parametric resonance involving all three degrees of freedom. We solve the nonperturbative quantum dynamics in the strong coupling regime of the nonlinear resonance, taking into account quantization, dissipation, and fluctuations of all fields. We find analytic solutions for quantum states in the rotating wave approximation which demonstrate tripartite quantum entanglement once the strong coupling regime is reached. We show how the strong coupling at the nonlinear resonance modifies photon emission and vibrational spectra, and how the observed spectra can be used to extract information about relaxation rates and the nonlinear coupling strength in specific systems.

quant-ph↗

arXiv2021

Quantum dynamics of open many-qubit systems strongly coupled to a quantized electromagnetic field in dissipative cavities

We study quantum dynamics of many-qubit systems strongly coupled to a quantized electromagnetic cavity mode, in the presence of decoherence and dissipation for both fermions and cavity photons. The analytic solutions are derived for a broad class of open quantum systems in Lindblad approximation. They include identical qubits, an ensemble of qubits with a broad distribution of transition frequencies, and multi-level electron systems. Compact analytic solutions for time-dependent quantum state amplitudes and observables become possible with the use of the stochastic equation of evolution for the state vector. We show that depending on the initial quantum state preparation, the systems can evolve into a rich variety of entangled states with destructive or constructive interference between the qubits. In particular, dissipation in a cavity can drive the system into the dark states completely decoupled from the cavity modes. We also find the regimes in which multi-electron systems with a broad distribution of transition frequencies couple to the quantized cavity field as a giant collective dipole.

quant-ph↗

arXiv2020

Dynamics and control of entangled electron-photon states in nanophotonic systems with time-variable parameters

We study the dynamics of strongly coupled nanophotonic systems with time-variable parameters. The approximate analytic solutions are obtained for a broad class of open quantum systems including a two-level fermion emitter strongly coupled to a multimode quantized electromagnetic field in a cavity with time-varying cavity resonances or the electron transition energy. The coupling of the fermion and photon subsystems to their dissipative reservoirs is included within the stochastic equation of evolution approach, which is equivalent to the Lindblad approximation in the master equation formalism. The analytic solutions for the quantum states and the observables are obtained under the approximation that the rate of parameter modulation and the amplitude of the frequency modulation are much smaller than the optical transition frequencies. At the same time, they can be arbitrary with respect to the generalized Rabi oscillations frequency which determines the coherent dynamics. Therefore, our analytic theory can be applied to an arbitrary modulation of the parameters, both slower and faster than the Rabi frequency, for complete control of the quantum state. In particular, we demonstrate protocols for switching on and off the entanglement between the fermionic and photonic degrees of freedom, swapping between the quantum states, and the decoupling of the fermionic qubit from the cavity field due to modulation-induced transparency.

quant-ph↗

arXiv2020

Relaxation operator for quasiparticles in a solid

Popular models of the phenomenological relaxation operators that are widely used in the master equation formalism for open condensed-matter systems have significant flaws ranging from limited applicability to violation of fundamental physical principles. We propose a relatively simple universal model of the relaxation operator which is free from these flaws, has a correct static limit, correct direct-current limit in a uniform electric field, includes both interband and intraband transitions, and is valid for an arbitrary dispersion of quasiparticles in a solid. We use the proposed operator to generalize the Lindhard formula and derive explicit expressions for the relaxation operator for Dirac materials with an unconventional energy spectrum of quasiparticles, such as graphene and Weyl semimetals. We compare the linear susceptibility spectra for graphene obtained with different relaxation models and show that the proposed relaxation operator leads to physically meaningful behavior of the susceptibility at low frequencies whereas the existing models become completely invalid.

cond-mat.mes-hall↗

arXiv2020

Generation and dynamics of entangled fermion-photon-phonon states in nanocavities

We develop the analytic theory describing the formation and evolution of entangled quantum states for a fermionic quantum emitter coupled to a quantized electromagnetic field in a nanocavity and quantized phonon or mechanical vibrational modes. The theory is applicable to a broad range of cavity quantum optomechanics problems and emerging research on plasmonic nanocavities coupled to single molecules and other quantum emitters. The optimal conditions for a tri-state entanglement are realized near the parametric resonances in a coupled system. The model includes decoherence effects due to coupling of the fermion, photon, and phonon subsystems to their dissipative reservoirs within the stochastic evolution approach, which is derived from the Heisenberg-Langevin formalism. Our theory provides analytic expressions for the time evolution of the quantum state and observables, and the emission spectra. The limit of a classical acoustic pumping and the interplay between parametric and standard one-photon resonances are analyzed.

quant-ph↗

arXiv2019

Extreme anisotropy and gyrotropy of surface polaritons in Weyl semimetals

Weyl semimetals possess unique electrodynamic properties due to a combination of strongly anisotropic and gyrotropic bulk conductivity, surface conductivity, and surface dipole layer. We explore the potential of popular tip-enhanced optical spectroscopy techniques for studies of bulk and surface topological electron states in these materials. Anomalous dispersion, extreme anisotropy, and the optical Hall effect for surface polaritons launched by a nanotip provides information about Weyl node position and separation in the Brillouin zone, the value of the Fermi momentum, and the matrix elements of the optical transitions involving both bulk and surface electron states.

cond-mat.mes-hall↗

arXiv2017

Magneto-polaritons in Weyl semimetals in a strong magnetic field

Exotic topological and transport properties of Weyl semimetals generated a lot of excitement in the condensed matter community. Here we show that Weyl semimetals in a strong magnetic field are highly unusual optical materials. The propagation of electromagnetic waves is affected by an interplay between plasmonic response of chiral Weyl fermions and extreme anisotropy induced by a magnetic field. The resulting magneto-polaritons possess a number of peculiar properties, such as hyperbolic dispersion, photonic stop bands, coupling-induced transparency, and broadband polarization conversion. These effects can be used for optical spectroscopy of these materials including detection of the chiral anomaly, or for broadband terahertz/infrared applications.

cond-mat.mes-hall↗

arXiv2016

Squeezing of thermal fluctuations in four-wave mixing in a Λ-scheme

We theoretically investigate the mechanism of two-mode quadrature squeezing in regime of four-wave mixing in a Λ-scheme of three-level atoms embedded in a thermal reservoir. We demonstrate that the process of nonlinear transfer of noise from the low frequency of ground state splitting to the optical frequency drastically modifies the condition of effective two-mode squeezing. The damage factor is significant if number of thermal photons at the low frequency is high and the role of inelastic processes in ground state coherence decay is not negligible. We found the optimal conditions for squeezing, in particular optimal density-length product of active medium depending on the relaxation parameters and drive intensity.

physics.optics↗

arXiv2015

The fluctuation-dissipation relation in a resonantly driven quantum medium

We calculate the radiation noise level associated with the spontaneous emission of a coherently driven medium. The significant field-induced modification of relation between the noise power and damping constant in a thermal reservoir is obtained. The nonlinear noise exchange between different atomic frequencies leads to violation of standard relations dictated by the fluctuation-dissipation theorem.

quant-ph↗

arXiv2014

Superradiant Decay of Cyclotron Resonance of Two-Dimensional Electron Gases

We report on the observation of collective radiative decay, or superradiance, of cyclotron resonance (CR) in high-mobility two-dimensional electron gases in GaAs quantum wells using time-domain terahertz magnetospectroscopy. The decay rate of coherent CR oscillations increases linearly with the electron density in a wide range, which is a hallmark of superradiant damping. Our fully quantum mechanical theory provides a universal formula for the decay rate, which reproduces our experimental data without any adjustable parameter. These results firmly establish the many-body nature of CR decoherence in this system, despite the fact that the CR frequency is immune to electron-electron interactions due to Kohn's theorem.

cond-mat.mes-hall↗