Strong Microwave Field Research Articles

Implementing N-quantum phase gate via circuit QED with qubit–qubit interaction

We propose a method for realizing a quantum phase gate of one qubit simultaneously controlling [Formula: see text] target qubits based on the qubit–qubit interaction. We show how to implement the proposed gate with one transmon qubit simultaneously controlling [Formula: see text] transmon qubits in a circuit QED driven by a strong microwave field. In our scheme, the operation time of this phase gate is independent of the number [Formula: see text] of qubits. On the other hand, this gate can be realized in a time of nanosecond-scale much smaller than the decoherence time and dephasing time both being the time of microsecond-scale. Numerical simulation of the occupation probabilities of the second excited lever shows that the scheme could be achieved efficiently within current technology.

Double-EIT laser cooling via amplitude and phase control of a microwave field

Abstract We consider the ground state cooling of a trapped four-level tripod atom which is phase-dependent double electromagnetically induced transparency (EIT) structure. We investigate the different effects of the phase adjustment under the weak and the strong microwave field conditions. In comparison with the situation of the double-EIT ground state cooling without microwave field, it is shown that the rate of ground-state cooling can be controlled via the amplitude and phase of the microwave field. With the phase being chosen as zero, the optimal cooling efficiency can be achieved. In this case, the cooling effect dominates the cooling procedure in the whole frequency range. We use the dressed-state model to explain the results.

Dissociation of systems of nonlinearly coupled particles in external fields according to a diffusion model

We have studied a diffusion model of the excitation and decay of a system of coupled particles in an external field. Using the example of a hydrogen chloride molecule, it is shown that electron oscillations exhibit chaotization that leads to diffusion ionization (or dissociation) in a sufficiently strong microwave field. The dependence of the rate of diffusion ionization on the radiation intensity and ellipticity of polarization and on the energy of excitation of the vibrational and rotational degrees of freedom has been numerically simulated. It is established that the ionization time significantly exceeds the period of electron motion over the undisturbed orbit.

The Effect of Light on the CVC of Strained p-n-Junction in a Strong Microwave Field

For the first time the effect of light on the CVC of strained p-n-junction in a strong microwave field is examined. It is shown that the deformation and the microwave field increase the current through p-n-junction, and the light decreases it. The mechanism of this phenomenon is explained by the fact that under heating of the charge carriers by microwave field the recombination current arises, and under the action of light the generation current arises which are directed oppositely. And under the influence of the deformation the band gap of the semiconductor will be changed.

Active and Capacitive Conductance of the Diode in a Strong Microwave Field

It is shown that the mean value of the capacitive current arising in the p-n-junction in a microwave field is zero, and the average value of the active current independently of the current value is different from zero and is equal to the current generated by the diode.

Influence of Deformation on CVC p-n-Junction in a Strong Microwave Field

This paper investigates the current-voltage characteristics (CVC) strain of p-n-junction in a strong microwave (MW) field and shows that the deformation increases the current generated in the p-n-junction. We analyze the current-voltage characteristics of p-n-junction in which three-dimensional space (I,U,e) gives more complete information than the two-dimensional.

EMF of Hot Charge Carriers Arising at the p-n-Junction under the Influence of the Microwave Field and Light

It is shown that the increase in the current of an asymmetric p-n-junction, caused by perturbation of potential barrier height and increasing recombination current in a strong microwave field, is suppressed by light generated photo carriers, leading to the displacement of current-voltage characteristics of p-n-junction into the direction of smaller current values.

Amplification without population inversion in tree-level system driven by an additional microwave field

In this paper, we investigate the spectrum properties of the lasing without population inversion in a three-level atomic system under an action of an externally applied microwave field. The probed absorption spectrum is obtained by solving the density matrix equation of this system. The results show that the absorption profile has a multi-peak structure, and exhibits obviously negative absorption (light amplification) in a specific range under the action of strong microwave field. The characteristic of the light amplification without population inversion according to the three level atomic system is demonstrated by the quantitative analysis of populations related to the probe levels.

Effect of microwave radiation on the properties of sintered oxide ceramics

Recent research has been significantly increased our fundamental understanding of microwave interactions with materials. Thermal absorption has been demonstrated to result from simultaneous action of multiple dissipation mechanisms during processing. In addition, it has been conclusively established that strong microwave fields exert a non-thermal driving force during sintering. This force acts as an additional driving force for atomic transport. For strong electric fields, the force can enhance diffusion rates during ceramic sintering. This paper describes recent research on microwave sintering of two oxide ceramics, a silica xerogel ceramic produced from rice husk ash (RHA) and a high purity alpha alumina. A millimeter waves (MMW) heating system with a 28 GHz gyrotron is applied for microwave sintering experiment. The ceramics were also sintered by using an electric furnace where served as comparison. Effect of microwave energy on the porosity reduction of the ceramics was investigated. Some possible physical mechanisms were discussed.

Quasiparticle tunneling in a periodically driven bosonic Josephson junction

A resonantly driven bosonic Josephson junction supports stable collective excitations, or quasiparticles, which constitute analogs of the Trojan wave packets previously explored with Rydberg atoms in strong microwave fields. We predict a quantum beating effect between such symmetryrelated many-body Trojan states taking place on time scales which are long in comparison with the driving period. Within a mean-field approximation, this quantum beating can be regarded as a manifestation of dynamical tunneling. On the full N-particle level, the beating phenomenon leads to an experimentally feasible, robust strategy for probing highly entangled mesoscopic states.

Double-layer particlespout in strong and nonuniform microwave fields

We report a new phenomenon named particlespout in which the particles spout in a specially designed microwave cavity. An ionic crystal of sodium chloride was heated in the microwave applicator. Beyond the melting point, the particles began to evaporate and move upward owing to thermal convection. These particles formed a funnel shape similar to a waterspout but they had two layers. In comparison with conventional heating, only a single but unstable columnar vortex can be observed. A theoretical model is proposed that attributes the observed phenomenon to the rotational kinematics together with the ponderomotive force. These two effects confine the particles to the inner and outer bounds, respectively.

Micro to mesoscale temperature gradients in microwave heated energetic materials

Temperature gradients will appear in any microwave-heated heterogeneous system where there is contrast in the complex permittivity of the constituent materials. The magnitude of the gradients depends on several factors that include the permittivity, thermal conductivity, length scale, and thermal diffusivity. In general, it is challenging to measure the absolute temperature accurately in a strong microwave field; the presence of large gradients can further complicate the interpretation of temperature measurements. These issues are especially important during the microwave heating of highly exothermic chemical reaction systems, such as those containing explosives or propellants. It was therefore the intent of this work to theoretically and numerically investigate the nature of microwave-induced thermal gradients in energetic systems over a wide range of length scales, primarily for the purpose of interpreting temperature measurement.

Spectrum of quasistable states in a strong microwave field

When atoms are exposed to intense laser or microwave pulses ~10% of the atoms are found in Rydberg states subsequent to the pulse, even if it is far more intense than required for static field ionization. The optical spectra of the surviving Li atoms in the presence of a 38 GHz microwave field suggest how atoms survive an intense pulse. The spectra exhibit a periodic train of peaks 38 GHz apart. One peak is just below the limit, and with a 90 V/cm field amplitude the train extends from 300 GHz above the limit to 3000 GHz below it. The spectra and quantum mechanical calculations imply that the atoms survive in quasi stable states in which the Rydberg electron is in a weakly bound orbit infrequently returning to the ionic core during the intense pulse.

Effect of Microwave Field on the Emergence of the Electromotive Force in Asymmetrical P-N-Junction

In asymmetric p-n-junction in a strong microwave field for the analysis of voltage and current necessary to consider both the heating of electrons and holes. total current and voltage generated is determined not by the temperature of the hot electrons and the temperature of the carriers that are decisive. three-dimensional image on the surface f(jsc,Te Th,) and f (Uoc Te Th) to determine the possible range of the voltages and currents generated by the p-n-junction in a strong microwave field.

Optical Bistability and Multistability in an EIT Medium with Two-Photon Resonance Transitions

Intensity threshold of optical bistability (OB) and optical multistability (OM) can be controlled by amplitude and phase control of microwave driven field in the two-photon resonance transitions in a parametric region. It is found that in two-photon resonance case, the weak microwave field can reduce the threshold of optical bistability and strong microwave field can lead to optical multistability. The effect of relative phase between applied fields is also discussed. It is shown that for weak and strong microwave field, intensity threshold of OB and OM can be modified. Moreover, it is found that for strong microwave field, relative phase has an essential role for switching between OB and OM or vice versa.

Dynamic nuclear polarisation via the integrated solid effect II: experiments on naphthalene-h8 doped with pentacene-d14

In dynamic nuclear polarisation (DNP), also called hyperpolarisation, a small amount of unpaired electron spins is added to the sample containing the nuclear spins, and the polarisation of these unpaired electron spins is transferred to the nuclear spins by means of a microwave field. Traditional DNP polarises the electron spin of stable paramagnetic centres by cooling down to low temperature and applying a strong magnetic field. Then weak continuous wave microwave fields are used to induce the polarisation transfer. Complicated cryogenic equipment and strong magnets can be avoided using short-lived photo-excited triplet states that are strongly aligned in the optical excitation process. However, a much faster transfer of the electron spin polarisation is needed and pulsed DNP methods like nuclear orientation via electron spin locking (NOVEL) and the integrated solid effect (ISE) are used.To describe the polarisation transfer with the strong microwave fields in NOVEL and ISE, the usual perturbation methods cannot be used anymore. In the previous paper, we presented a theoretical approach to calculate the polarisation transfer in ISE. In the present paper, the theory is applied to the system naphthalene-h8 doped with pentacene-d14 yielding the photo-excited triplet states and compared with experimental results.

Dynamic nuclear polarisation via the integrated solid effect I: theory

In the hyperpolarisation method known as dynamic nuclear polarisation (DNP), a small amount of unpaired electron spins is added to the sample containing the nuclear spins and the polarisation of these unpaired electron spins is transferred to the nuclear spins by means of a microwave field. Traditional DNP uses weak continuous wave (CW) microwave fields, so perturbation methods can be used to calculate the polarisation transfer. A much faster transfer of the electron spin polarisation is obtained with the integrated solid effect (ISE) which uses strong pulsed microwave fields. As in nuclear orientation via electron spin locking, the polarisation transfer is coherent, similar to the coherence transfer between nuclear spins. This paper presents a theoretical approach to calculate this polarisation transfer.ISE is successfully used for a fast polarisation transfer from short-lived photo-excited triplet states to the surrounding nuclear spins in molecular crystals. These triplet states are strongly aligned in the photo-excitation process and do not require the low temperatures and strong magnetic fields needed to polarise the electron spins in traditional DNP. In the following paper, the theory is applied to the system naphthalene-h8 doped with pentacene-d14 which provides the photo-excited triplet states, and compared with experimental results.

Generation of the quadripartite Greenberger–Horne–Zeilinger entangled state in quantum beat lasers

In this letter, a scheme is presented to obtain quadripartite Greenberger–Horne–Zeilinger (GHZ) entanglement via quantum beats in a four-level diamond configuration atomic system. When the top and the ground states are initially prepared in a coherent superposition, the four quantized fields coupling with four dipole-allowed transitions can be correlated with each other by using a strong microwave field to drive the dipole-forbidden transition. It is the combined effect of atomic coherence-controlled correlated-spontaneous emission and double quantum beats that results in the quadripartite GHZ-type entanglement. Our numerical results show that the quadripartite entanglement, which can be controlled effectively by varying the amplitude and phase of the microwave field, occurs in a very wide parameter range. In addition, using input–output theory, we find that the output quadripartite entanglement is robust against thermal fluctuations, which may be useful for long-distance quantum communications.

Pulse propagation in atomic media in the triangular configuration

Weak probe-pulse propagation is studied in a three-level atomic system irradiated by a strong control laser field and a strong microwave field in the closed-loop triangular (Δ) configuration. In addition to the direct absorption channel, a second channel is activated in which a probe photon’s absorption is replaced by its emission accompanied by an absorption of two control and two microwave photons. The pulse can be considered a superposition of two components, each of which experiences a separated effective susceptibility, exhibiting its absorption/gain windows. The evolution of the pulse spectrum in space and the pulse evolution in space–time are discussed. In particular it is shown that the number and positions of the spectrum peaks change and the pulse exhibits beats. In addition to the propagating field, a stationary light generated by the sample is also discussed.

Nuclear-spin-dependent coherent population trapping of single nitrogen-vacancy centers in diamond

Coherent population trapping (CPT) provides a highly sensitive means for probing the energy level structure of an atomic system. For a nitrogen vacancy center in diamond, the CPT offers an alternative to the standard optically-detected magnetic resonance method for measuring the hyperfine structure of the electronic ground states. We show that the nuclear spin dependent CPT measures directly the hyperfine splitting of these states due to the 14N nuclear spin. The CPT spectral response obtained in the presence of a strong microwave field, resonant or nearly resonant with a ground state spin transition, maps out the dynamic Stark splitting induced by the coherent spin excitation.