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J. W. Yu

Publications and source records attributed to J. W. Yu.

12 recordsLinked to original sources
arXiv2026

Multi-Modal Spectroscopy Theory for Ultrafast Control of Rabi Oscillations

We propose a three-cavity scheme to realize full control of the emitter-cavity coupling strength in cavity quantum electrodynamics (cQED). The involvement of coupled oscillators gives rise to transient dynamics comprising multiple spectral components, which significantly increases the numerical cost to resolve the fluorescence spectrum in the time domain. A generalized sensor method is hence developed to simplify the calculation process for the characterization of nonstationary quantum dynamics. Multi-modal spectroscopy reveals the emergence, splitting, and disappearance of supermodes in real time. Based on the depletion of the zero-energy supermode, ultrafast switching of Rabi oscillations is demonstrated for time-domain multi-modal spectroscopy. These results exhibit a consistent picture from the spectral control of multiple oscillators to the quantum observation in ultrafast dynamics, which establishes the sensor method as a powerful theoretical tool for the ultrafast spectroscopy of cQED systems.

quant-ph↗
arXiv2026

Phase-preserving control of Floquet-engineered cavity quantum electrodynamics

We propose a Floquet-engineered framework for the coherent control of the light-matter interaction in a two-level system (TLS) located in a time-modulated cavity. Strictly phase-preserving operation of the TLS-cavity interaction is demonstrated, allowing the interrupt and retrieval of coherent Rabi oscillations without the loss of quantum information. By introducing a phonon reservoir, it is proved that the frequency instability induced from non-Markovian processes does not produce significant phase decoherence during Floquet modulation. Our results provide new insights into the fundamental physics of a driven quantum system and establish Floquet engineering as a powerful tool for coherent quantum information processing.

quant-ph↗
arXiv2025

Enhancing Photon Indistinguishability of Spectrally Mismatched Single Photons by Cavity Floquet Engineering

We theoretically propose a scheme to enhance the photon indistinguishability of spectrally mismatched single photons via Floquet-engineered optical frequency combs (OFCs) in cavity quantum electrodynamic systems. By periodically modulating two distinct single-photon states under a modulation frequency which is exactly equal to the spectral mismatch of two cavity modes, a pair of single-photon frequency-comb (SPFC) states is prepared energy-conservatively based on full unitary operations. The two states show high indistinguishability with an ideal $g^{(2)}_\mathrm{HOM}(0)$ down to zero due to the superposition of intensity-matched single-photon states coherently distributed across the teeth of the combs.

quant-ph↗
arXiv2023

Thermal hysteretic behavior and negative magnetoresistance in an unusual charge-density-wave material EuTe4

EuTe4 is a newly-discovered van der Waals material exhibiting a novel charge-density wave (CDW) with a large thermal hysteresis in the resistivity and CDW gap. In this work, we systematically study the electronic structure and transport properties of EuTe4 using high-resolution angle-resolved photoemission spectroscopy (ARPES), magnetoresistance measurements, and scanning tunneling microscopy (STM). We observe a CDW gap of about 200 meV at low temperatures that persists up to 400 K, suggesting that the CDW transition occurs at a much higher temperature. We observe a large thermal hysteretic behavior of the ARPES intensity near the Fermi level, consistent with the resistivity measurement. The hysteresis in the resistivity measurement does not change under a magnetic field up to 7 T, excluding the thermal magnetic hysteresis mechanism. Instead, the surface topography measured with STM shows surface domains with different CDW trimerization directions, which may be important for the thermal hysteretic behavior of EuTe4. Interestingly, we observe a large negative magnetoresistance at low temperatures that can be associated with the canting of magnetically ordered Eu spins. Our work shed light on the understanding of magnetic, transport, and electronic properties of EuTe4.

cond-mat.str-el↗
arXiv2012

Absorption features caused by oscillations of electrons on the surface of a quark star

If quark stars exist, they may be enveloped in thin electron layers (electron seas), which uniformly surround the entire star. These layers will be affected by the magnetic fields of quark stars in such a way that the electron seas would transmit hydromagnetic cyclotron waves, as studied in this paper. Particular attention is devoted to vortex hydrodynamical oscillations of the electron sea. The frequency spectrum of these oscillations is derived in analytic form. If the thermal X-ray spectra of quark stars are modulated by vortex hydrodynamical vibrations, the thermal spectra of compact stars, foremost central compact objects (CCOs) and X-ray dim isolated neutron stars (XDINSs), could be used to verify the existence of these vibrational modes observationally. The central compact object 1E 1207.4-5209 appears particularly interesting in this context, since its absorption features at 0.7 keV and 1.4 keV can be comfortably explained in the framework of the hydro-cyclotron oscillation model.

astro-ph.HE↗
arXiv2011

Vibration Powered Radiation of Quaking Magnetar

In juxtaposition with the standard model of rotation powered pulsar, the model of vibration powered magnetar undergoing quake-induced torsional Alfven vibrations in its own ultra strong magnetic field experiencing decay is considered. The presented line of argument suggests that gradual decrease of frequencies (lengthening of periods) of long-periodic pulsed radiation detected from a set of X-ray sources can be attributed to magnetic-field-decay induced energy conversion from seismic vibrations to magneto-dipole radiation of quaking magnetar.

astro-ph.HE↗
arXiv2011

Pulsating magneto-dipole radiation of a quaking neutron star powered by energy of Alfven seismic vibrations

We compute the characteristic parameters of magnetic dipole radiation of a neutron star undergoing torsional seismic vibrations under the action of Lorentz restoring force about axis of a dipolar magnetic field experiencing decay. After brief outline of general theoretical background of the model of vibration powered neutron star, we present numerical estimates of basic vibration and radiation characteristics, such as the oscillation frequency, lifetime, luminosity of radiation, and investigate their time dependence upon magnetic field decay. The presented analysis suggests that gradual decrease in frequencies of pulsating high-energy emission detected from a handful of currently monitored AXP/SGR-like X-ray sources can be explained as being produced by vibration powered magneto-dipole radiation of quaking magnetars. \keywords{neutron stars, torsion Alfvén vibrations, vibration powered radiation, magnetic field decay, magnetars}

astro-ph.HE↗
arXiv2011

On Hoyle-Narlikar-Wheeler mechanism of vibration energy powered magneto-dipole emission of neutron stars

We revisit the well-known Hoyle-Narlikar-Wheeler proposition that neutron star emerging in the magnetic-flux-conserving process of core-collapse supernova can convert the stored energy of Alfven vibrations into power of magneto-dipole radiation. We show that the necessary requirement for the energy conversion is the decay of internal magnetic field. In this case the loss of vibration energy of the star causes its vibration period, equal to period of pulsating emission, to lengthen at a rate proportional to the rate of magnetic field decay. These prediction of the model of vibration powered neutron star are discussed in juxtaposition with data on pulsating emission of magnetars whose radiative activity is generally associated with the decay of ultra strong magnetic field.

astro-ph.HE↗
arXiv2011

Radiative activity of magnetic white dwarf undergoing Lorentz-force-driven torsional vibrations

We study radiative activity of magnetic white dwarf undergoing torsional vibrations about axis of its own dipole magnetic moment under the action of Lorentz restoring force. It is shown that pulsating white dwarf can convert its vibration energy into the energy of magneto-dipole emission, oscillating with the frequency equal to the frequency of Alfvén torsional vibrations, provided that internal magnetic field is decayed. The most conspicuous feature of the vibration energy powered radiation in question is the lengthening of periods of oscillating emission; the rate of period elongation is determined by the rate magnetic field decay.

astro-ph.SR↗
arXiv2010

Quaking neutron star deriving radiative power of oscillating magneto-dipole emission from energy of Alfvén seismic vibrations

It is shown that depletion of the magnetic field pressure in a quaking neutron star undergoing Lorentz-force-driven torsional seismic vibrations about axis of its dipole magnetic moment is accompanied by the loss of vibration energy of the star that causes its vibration period to lengthen at a rate proportional to the rate of magnetic field decay. Highlighted is the magnetic-field-decay induced conversion of the energy of differentially rotational Alfvén vibrations into the energy of oscillating magneto-dipole radiation. A set of representative examples of magnetic field decay illustrating the vibration energy powered emission with elongating periods produced by quaking neutron star are considered and discussed in the context of theory of magnetars.

astro-ph.HE↗
arXiv1995

High Dynamic Range Imaging Using a Deformable Mirror for Space Coronography

The need for high dynamic range imaging is crucial in many astronomical fields, such as extra-solar planet direct detection, extra-galactic science and circumstellar imaging. Using a high quality coronograph, dynamic ranges of up to $10^{5}$ have been achieved. However the ultimate limitations of coronographs do not come from their optical performances, but from scattering due to imperfections in the optical surfaces of the collecting system. We propose to use a deformable mirror to correct these imperfections and decrease the scattering level in local regions called ``dark holes''. Using this technique will enable imaging of fields with dynamic ranges exceeding $10^8$. We show that the dark-hole algorithm results in a lower scattering level than simply minimizing the RMS figure error (maximum-strehl-ratio algorithm). The achievable scattering level inside the dark-hole region will depend on the number of mirror actuators, the surface quality of the telescope, the single-actuator influence function and the observing wavelength. We have simulated cases with a $37\times37$ deformable mirror using data from the {\it Hubble Space Telescope\/} optics without spherical aberrations and have demonstrated dark holes with rectangular and annular shapes. We also present a preliminary concept of a monolithic, fully integrated, high density deformable mirror which can be used for this type of space application.

astro-ph↗