arXiv subjects

Masao Kitano

Publications and source records attributed to Masao Kitano.

32 records · Page 2Linked to original sources

arXiv2013

Storage of electromagnetic waves in a metamaterial that mimics electromagnetically induced transparency

We propose a method for dynamically controlling the properties of a metamaterial that mimics electromagnetically induced transparency (EIT) by introducing varactor diodes to manipulate the structural symmetry of the metamaterial. Dynamic modulation of the EIT property enables the storage and retrieval of electromagnetic waves. We confirmed that the electromagnetic waves were stored and released, while maintaining the phase distribution in the propagating direction.

physics.optics↗

arXiv2012

Weak measurements with completely mixed probe states

Weak measurements with mixed probe states were investigated in the presence of noise in the probe system. We show that the completely mixed state can be used as a probe state for weak measurements of imaginary weak values. The completely mixed probe state has some advantages in terms of noise tolerance. We also experimentally demonstrated weak measurements of polarization rotation via unpolarized light, which corresponds to weak measurements with completely mixed probe states in a two-state system.

quant-ph↗

arXiv2012

Observation of flat band for terahertz spoof plasmon in metallic kagomé lattice

We study the dispersion relation of a metamaterial composed of metallic disks and bars arranged to have kagome symmetry and find that a plasmonic flat band is formed by the topological nature of the kagome lattice. To confirm the flat-band formation, we fabricate the metamaterial and make transmission measurements in the terahertz regime. Two bands formed by transmission minima that depend on the polarization of the incident terahertz beams are observed. One of the bands corresponds to the flat band, as confirmed by the fact that the resonant frequency is almost independent of the incident angle.

physics.optics↗

arXiv2012

Variable group delay in a metamaterial with field-gradient-induced transparency

We realize variable control of the group delay in an electromagnetically induced transparency-like metamaterial. Its unit cell is designed to have a bright mode and a dark mode. The coupling strength between these two modes is determined by the electromagnetic field gradient. In this metamaterial with field-gradient-induced transparency, the group delay at the transparency frequency can be varied by varying the incident angle of the electromagnetic plane waves. By tilting a single layer of the metamaterial, the group delay of a microwave pulse can be varied between 0.50 and 1.85 ns.

physics.optics↗

arXiv2012

Efficient second harmonic generation in a metamaterial with two resonant modes coupled through two varactor diodes

We present an effective method to generate second harmonic (SH) waves using nonlinear metamaterial composed of coupled split ring resonators (CSRRs) with varactor (variable capacitance) diodes. The CSRR structure has two resonant modes: a symmetric mode that resonates at the fundamental frequency and an anti-symmetric mode that resonates at the SH frequency. Resonant fundamental waves in the symmetric mode generate resonant SH waves in the anti-symmetric mode. The double resonance contributes to effective SH radiation. In the experiment, we observe 19.6 dB enhancement in the SH radiation in comparison with the nonlinear metamaterial that resonates only for the fundamental waves.

physics.optics↗

arXiv2011

Enhancement of second harmonic generation in a doubly resonant metamaterial

We investigate second harmonic (SH) generation in a doubly resonant metamaterial. We show that SH generation can be enhanced when the resonant condition is satisfied for the SH frequency as well as for the fundamental frequency. A unit cell of the doubly resonant metamaterial consists of two coupled resonators, one of which resonates at the fundamental frequency, whereas the other resonates around the SH frequency. We observe that the SH generation in the doubly resonant metamaterial is 4.6 times as large as that in a singly resonant metamaterial.

physics.optics↗

arXiv2011

Electromagnetic response of a metamaterial with field-gradient-induced transparency

We investigate a dynamically controllable electromagnetically induced transparency-like metamaterial. The unit structure of the metamaterial consists of a low-quality-factor resonator and a high-quality-factor resonator. The field gradient of the incident electromagnetic wave in the transverse direction induces coupling between these two types of resonators and causes a transparency phenomenon. We present the simulation and experimental results for the dynamic control of the electromagnetic response.

physics.optics↗

arXiv2011

Bloch sphere representation of three-vertex geometric phases

The properties of the geometric phases between three quantum states are investigated in a high-dimensional Hilbert space using the Majorana representation of symmetric quantum states. We found that the geometric phases between the three quantum states in an N-state quantum system can be represented by N-1 spherical triangles on the Bloch sphere. The parameter dependence of the geometric phase was analyzed based on this picture. We found that the geometric phase exhibits rich nonlinear behavior in a high-dimensional Hilbert space.

quant-ph↗

arXiv2009

Geometrical aspects of weak measurements and quantum erasers

We investigate the mechanism of weak measurement by using an interferometric framework. In order to appropriately elucidate the interference effect that occurs in weak measurement, we introduce an interferometer for particles with internal degrees of freedom. It serves as a framework common to quantum eraser and weak measurement. We demonstrate that the geometric phase, particularly the Pancharatnam phase, results from the post-selection of the internal state, and thereby the interference pattern is changed. It is revealed that the extraordinary displacement of the probe wavepackets in weak measurement is achieved owing to the Pancharatnam phase associated with post-selection.

quant-ph↗

arXiv2009

Full Quantum Analysis of Two-Photon Absorption Using Two-Photon Wavefunction: Comparison with One-Photon Absorption

For dissipation-free photon-photon interaction at the single photon level, we analyze one-photon transition and two-photon transition induced by photon pairs in three-level atoms using two-photon wavefunctions. We show that the two-photon absorption can be substantially enhanced by adjusting the time correlation of photon pairs. We study two typical cases: Gaussian wavefunction and rectangular wavefunction. In the latter, we find that under special conditions one-photon transition is completely suppressed while the high probability of two-photon transition is maintained.

quant-ph↗

arXiv2009

Two-photon interference of photon pairs created in photonic crystal fibers

We investigate a method to produce photon pairs by four-wave mixing in photonic crystal fibers (PCFs). By controlling the wavelength of the pump light, which determines the phase matching condition for four-wave mixing, we can obtain a broader spectrum of photon pairs than undesired Raman-scattered photons. We observe two-photon interference of photon pairs from a PCF with the help of an unbalanced Mach-Zehnder interferometer. Two-photon interference fringes with 83% visibility, which exceeds the classical limit of 50%, are obtained.

quant-ph↗

arXiv2008

Is the Heisenberg uncertainty relation really violated?

It has been pointed out that for some types of measurement the Heisenberg uncertainty relation seems to be violated. In order to save the situation a new uncertainty relation was proposed by Ozawa. Here we introduce revised definitions of error and disturbance taking into account the gain associated with generalized measurement interactions. With these new definitions, the validity of the Heisenberg inequality is recovered for continuous linear measurement interactions. We also examine the changes in distribution functions caused by the general measurement interaction and clarify the physical meanings of infinitely large errors and disturbances.

quant-ph↗

arXiv2006

Derivation of magnetic Coulomb's law for thin, semi-infinite solenoids

It is shown that the magnetic force between thin, semi-infinite solenoids obeys a Coulomb-type law, which corresponds to that for magnetic monopoles placed at the end points of each solenoid. We derive the magnetic Coulomb law from the basic principles of electromagnetism, namely from the Maxwell equations and the Lorentz force.

physics.class-ph↗

arXiv2006

The vacuum impedance and unit systems

In electromagnetism, the vacuum impedance $Z_0$ is a universal constant, which is as important as the velocity of light $c$ in vacuum. Unfortunately, however, its significance does not seem to be appreciated so well and sometimes the presence itself is ignored. It is partly because in the Gaussian system of units, which has widely been used for long time, $Z_0$ is a dimensionless constant and of unit magnitude. In this paper, we clarify that $Z_0$ is a fundamental parameter in electromagnetism and plays major roles in the following scenes: reorganizing the structure of the electromagnetic formula in reference to the relativity; renormalizing the quantities toward natural unit systems starting from the SI unit system; and defining the magnitudes of electromagnetic units.

physics.gen-ph↗