Nonclassical Electromagnetic Field Research Articles

Excitation of Semiconductor Nanosystems by Multy-Frequency Quantum Field

The formation of Frenkel excitons in a 2D semiconductor nanosystem induced by frequency-multimode non-classical electromagnetic field is investigated. Strong sensitivity of excitation dynamics to the initial states of quantum field modes is found. The possibility to manage the excitation dynamics and controllably enhance a certain excitation channel by varying field frequency detuning and by choosing a proper initial state of the non-classical multimode field is demonstrated. The specific features of the excitation arising due to efficient coupling and energy exchange between initially independent field frequency modes are demonstrated. The polarization response of the considered nanosystem on the multi-frequency field impact is studied and its peculiarities arising due to the quantum features of the affecting non-classical light are found.

Excitation of semiconductor nanosystems by a few-photon frequency-multimode optical field

The excitation of a semiconductor quantum nanosystem induced by a frequency-multimode nonclassical electromagnetic field is analytically investigated. The possibility to control the features and dynamics of different excitation channels by varying the weights and initial energy distribution in the considered field spectral modes is demonstrated. Strong coupling between different frequency modes is found to arise due to their interaction with electronic subsystem and is shown to influence dramatically on the excitation. The peculiarities of the excitation process induced by a multi-frequency Schmidt mode, which characterizes spectral distribution of squeezed vacuum light, are revealed. The optimal spectral profile of the Schmidt mode and initial energy distribution of different field spectral components providing the most efficient excitation of a nanosystem are found.

Currents in a Quantum Nanoring Controlled by Non-Classical Electromagnetic Field.

Quantum ring accommodating interacting spin-less fermions threaded by magnetic flux with a non-classical component added to a static, inducing persistent current, is considered. It is investigated how current flowing in the ring becomes affected by a state of non-classical flux and how Coulomb interaction between fermions influences entanglement of quantum ring and the driving field. In particular it is shown that in an absence of decoherence and under certain conditions fermion–fermion interaction is necessary for a ring–field entanglement to occur.

Quantum Entanglement and Phase Control of Nonclassical Electromagnetic Fields Interacting with Atomic Systems

The interaction of a three-level atom with two quantum field modes has been studied analytically. Strong quantum entanglement between individual parts of the considered multipartite system has been revealed and the possibility of its controlled variation has been demonstrated. Methods of the transmission and exchange of phase information between field modes, as well as of direct measurement of the phase characteristics of an unknown state of the input field, have been developed on the basis of quantum entanglement between initially independent quantum fields interacting with an atom.

Photoionization of Atomic Systems in Squeezed States of Light

The ionization of an atom by a nonclassical electromagnetic field has been studied by a method developed to obtain results for an arbitrary initial state of the field, including squeezed vacuum with a large average number of photons. Characteristics of the ionization of atomic systems by nonclassical squeezed light have been demonstrated for the first time. In contrast to the case of a coherent field, a significantly smoother decrease in the contributions of different above-threshold channels to ionization has been found. Features of photo-electron spectra in continuum have been revealed for the first time as a significant overlapping of peaks from different ionization channels.

Excitation of Atomic Systems by Nonclassical Electromagnetic Fields

Interaction between atomic systems and nonclassical electromagnetic fields is considered using the example of a two-level system. The dynamics of such characteristics as the population of atomic levels, the entanglement of field and atomic subsystems, and the distribution of the number of photons for an active field are investigated.

Emission of microwave photon pairs by a tunnel junction.

We report the observation of photon pairs in the photoassisted shot noise of a tunnel junction in the quantum regime at very high frequency and very low temperature. We have measured the fluctuations of the noise power generated by the junction at two different frequencies, f(1) = 4.4 and f(2) = 7.2 GHz, while driving the junction with a microwave excitation of frequency f(0) = f(1) + f(2). We observe clear correlations between the fluctuations of the two noise powers even when the mean photon number per measurement is much smaller than one. This is strong evidence for photons being emitted in pairs. We also demonstrate that the electromagnetic field generated by the junction exhibits two-mode amplitude squeezing, a proof of its nonclassicality. The data agree very well with predictions based on the fourth cumulant of the current fluctuations generated by the junction.

Stabilization of atoms in strong non-classical electromagnetic fields

The dynamics of an atom in a strong single mode non-classical electromagnetic cavity field is studied. The reconstruction of the energy spectrum of atom and the effect of the ionization suppression in the presence of non-classical field are discussed. It is found that Kramers – Henneberger mechanism of the ionization suppression is realized in strong nonclassical fields also. For squeezed vacuum states the threshold of the stabilization is approximately three times lower than for classical (coherent) state of the same intensity.

Dynamics of an atomic system in a strong non-classical electromagnetic field

The dynamics of an atom in a strong single mode non-classical electromagnetic cavity field is studied. The reconstruction of the energy spectrum of an atom and the effect of ionization suppression in the presence of a non-classical field are discussed. It is found that a mechanism of ionization suppression similar to the Kramers–Henneberger one is also realized in strong non-classical fields. For squeezed vacuum states the threshold of the stabilization is approximately three times lower than for a classical (coherent) state of the same intensity.

AC stark effect and atomic stabilization in a strong nonclassical electromagnetic field

We consider the dynamics of an atom that interacts with one mode of an electromagnetic field in a microcavity. We discuss the reconstruction of the spectrum of atomic states and the occurrence of a stabilization effect for the case of a nonclassical state of the field mode, in particular, a squeezed vacuum state. We show that, for nonclassical fields, an ionization-suppression effect also arises (stabilization), which is similar to the Kramers-Henneberger stabilization in a classical electromagnetic field, and, for squeezed states of the electromagnetic field, the stabilization threshold is several times smaller than that for the classical electro-magnetic field of the same intensity.

Dynamics of ionisation and entanglement in the 'atom + quantum electromagnetic field' system

The dynamics of a model Rydberg atom in a strong nonclassical electromagnetic field is investigated. The field-induced transitions to the continuum involving different numbers of photons (with intermediate states in the discrete spectrum) are taken into account and the specific features of ionisation in 'squeezed' fieldstates are considered in comparison with the case of classical light. A significant decrease in the ionisation rate is found, which is caused by the interference stabilisation of the atomic system. The entanglement of the atomic and field subsystems, the temporal dynamics of the correlations found, and the possibility of measuring them are analysed.

Magnetic flux in a mesoscopic SQUID controlled by nonclassical electromagnetic fields

We analyze SQUID coupled to a nonclassical electromagnetic field (NEM) and show that properties of the SQUID can be manipulated by a choice of a state of NEM. In particular, energy or fluctuations of magnetic flux threading the loop of the SQUID can be resolved into separate lines for each photon number state of one-mode NEM. The impact of two-mode NEM prepared in entangled Bell states is discussed. The findings suggest an experimental method of detection of photon states: the SQUID response is dependent on the number of photons in one-mode NEM and on the Bell states of a two-mode NEM.

Entanglement of distant flux qubits mediated by non-classical electromagneticfield

The mechanism for entanglement of two flux qubits each interacting with a single modeelectromagnetic field is discussed. By performing a Bell state measurement (BSM) onphotons we find the two qubits in an entangled state depending on the system parameters.We discuss the results for two initial states and take into consideration the influence ofdecoherence.

Electron interference in mesoscopic devices in the presence of nonclassical electromagnetic fields

The interaction of mesoscopic interference devices with nonclassical electromagnetic fields is studied. The external quantum fields induce a phase factor on the electric charges. This phase factor, which is a generalization of the standard Aharonov-Bohm phase factor, is in the case of nonclassical electromagnetic fields a quantum mechanical operator. Its expectation value depends on the density matrix describing the nonclassical photons and determines the interference. Several examples are discussed, which show that the quantum noise of the nonclassical photons destroys slightly the electron interference fringes. An interesting application arises in the context of distant electron interference devices, irradiated with entangled photons. In this case the interfering electrons in the two devices become entangled. The same ideas are applied in the context of SQUID rings irradiated with nonclassical electromagnetic fields. It is shown that the statistics of the Cooper pairs tunneling through the Josephson junction depend on the statistics of the photons.

Entanglement of distant electron interference experiments

Two electron interference experiments which are far from each other are considered. They are irradiated with correlated nonclassical electromagnetic fields, produced by the same source. The phase factors are in this case operators, and their expectation values with respect to the density matrix of the electromagnetic field quantify the observed electron fringes. The correlated photons create correlations between the observed electron intensities. Both cases of classically correlated (separable) and quantum mechanically correlated (entangled) electromagnetic fields are considered. It is shown that the induced correlation between the distant electron interferences is sensitive to the nature of the correlation between the irradiating photons.

Persistent currents in the presence of nonclassical electromagnetic fields

Persistent currents in mesoscopic rings and cylinders threaded by a magnetostatic flux and also by monochromatic nonclassical electromagnetic fields are considered. The results depend on the quantum state of the nonclassical electromagnetic fields. It is shown that quantum and thermal noise in the field reduces the current and can change its character from diamagnetic to paramegnetic, and vice versa. Four different examples of nonclassical electromagnetic fields are considered (number eigenstates, coherent states with randomized phase, coherent states, and thermal states) and the corresponding currents are calculated. Two-mode entangled electromagnetic fields are also considered, and the effect of entanglement on the currents is studied.

Mesoscopic Josephson arrays interacting with non-classical electromagnetic fields and their applications

A ring made from a Josephson array in the insulating phase is considered. The ring contains a ‘dual Josephson junction’ (Josephson junction for vortices). External non-classical electromagnetic fields are coupled to the device and interact with the vortices that circulate the ring. The time evolution of this two-mode fully quantum mechanical system is studied. The effect of the quantum statistics of the photons on the quantum statistics of the vortices is discussed. The entanglement between the two systems is quantified.

COLLAPSE AND REVIVAL IN VORTEX INTERFERENCE IN THE PRESENCE OF NONCLASSICAL ELECTROMAGNETIC FIELD

Interference of vortex winding around electric charges induced by nonclassical electromagnetic field is considered. It is shown that collapse and revival can exist in such a system, which is the effect of the quantum noise of the nonclassical electromagnetic field on the dynamic behavior of the vortex interference.

Bloch steps in vortex interference in the presence of classical and nonclassical electromagnetic fields

Interference of vortices winding around a time-dependent electric charge ${It+Q}_{0}\mathrm{sin}(\ensuremath{\omega}t)$ is considered. It is shown that the time-averaged intensity of vortices shows interference only if ${\ensuremath{\Phi}}_{0}I=N\ensuremath{\omega}$ (integral Bloch steps). The same phenomenon is studied for the electric charge ${Q(t)=Q}_{1}\mathrm{sin}({\ensuremath{\omega}}_{1}{t)+Q}_{0}\mathrm{sin}(\ensuremath{\omega}t)$ and it is shown that the time-averaged intensity of vortices shows interference only for rational values of the ratio ${\ensuremath{\omega}}_{1}/\ensuremath{\omega}$ (fractional Bloch steps). The case in which the electric charge is induced by nonclassical microwaves is also considered. Results for various examples of nonclassical microwaves (e.g., coherent states, squeezed states, etc.) are presented and a comparison with the corresponding classical case is made. It is shown that the quantum noise in the nonclassical microwaves causes partial destruction of the interference.

Biophoton emission in the evolution of a squeezed state of frequency stable damped oscillator

A model to explain the relaxation behaviour of a biophoton signal is developed. The model assumes that every biological system is endowed with a non-classical electromagnetic field in a squeezed state. The quantum evolution of the state determines the shape of the signal. It is illustrated by considering the evolution of a single mode field described by a frequency stable damped oscillator. The model predicts a relaxation behaviour in the form ( n( t) = B 0 + B 2(1 + λ 0 t) 2. The coefficients B 0 and B 2 depend upon the initial state of the field and are situation specific. The constant λ 0 is determined by the damping of the field and is system specific. The model explains in a natural way two characteristic features of biophoton signals, namely non-exponential decay of light induced emission and constant flux of spontaneous emission. The model is applied to the light induced photon emission in flowers of Tagetes Patula. The value of the damping coefficient λ 0 in this system is found to be (0.040 ± 0.011)s −1.