arXiv subjects

Po-Han Lin

Publications and source records attributed to Po-Han Lin.

4 recordsLinked to original sources

arXiv2021

Transient nuclear inversion by X-Ray Free Electron Laser in a tapered x-ray waveguid

By restricting the spatial energy transmission of an electromagnetic wave, dielectric waveguides transmit light over long distances at sustained intensity. Waveguides have been used in the microwave and optical range to maintain strong signal intensities in connection with lasers, but guiding of intense short-wavelength radiation such as x-rays has proven more cumbersome. Here we investigate theoretically how tapered x-ray waveguides can focus and guide radiation from x-ray free electron lasers. Elliptical waveguides using a cladding material with high atomic number such as platinum can maintain an x-ray intensity up to three orders of magnitude larger than in free space. This feature can be used to significantly enhance resonant interactions of x-rays, for instance driving nuclear transitions up to transient nuclear population inversion. This could be the first breakthrough in nuclear state population control. Our results anticipate the important role of tapered x-ray waveguides in the emerging field of x-ray quantum optics with nuclear transitions.

physics.optics↗

arXiv2020

Time-Delayed Magnetic Control and Narrowing of X-Ray frequency Spectra in Two-Target Nuclear Forward Scattering

Controlling and narrowing x-ray frequency spectra in magnetically perturbed two-target nuclear forward scattering is theoretically studied. We show that different hard-x-ray spectral redistributions can be achieved by single or multiple switching of magnetic field in nuclear targets. Our scheme can generate x-ray spectral lines with tenfold intensity enhancement and spectral width narrower than four times the nuclear natural linewidth. The present results pave the way towards a brighter and flexible x-ray source for precision spectroscopy of nuclear resonances using modern synchrotron radiation.

quant-ph↗

arXiv2019

Spectral control over $\gamma$-ray echo using a nuclear frequency comb system

Two kinds of spectral control over $\gamma$-ray echo using a nuclear frequency comb system are theoretically investigated. A nuclear frequency comb system is composed of multiple nuclear targets under magnetization (hyperfine splitting), mechanical motion (Doppler shift) or both, namely, moving and magnetized targets. In frequency domain the unperturbed single absorption line of $\gamma$-ray therefore splits into multiple lines with equal spacing and becomes a nuclear frequency comb structure. We introduce spectral shaping and dynamical splitting to the frequency comb structure respectively to optimize the use of a medium and to break the theoretical maximum of echo efficiency, i.e., 54\%. Spectral shaping scheme leads to the reduction of required sample resonant thickness for achieving high echo efficiency of especially a broadband input. Dynamical splitting method significantly advances the echo efficiency up to 67\% revealed by two equivalent nuclear frequency comb systems. We also show that using only few targets is enough to obtain good echo performance, which significantly eases the complexity of implementation. Our results extend quantum optics to 10keV regime and lay the foundation of the development of $\gamma$-ray memory.

quant-ph↗

arXiv2000

Base Encryption: Dynamic algorithms, Keys, and Symbol Set

All the current modern encryption algorithms utilize fixed symbols for plaintext and cyphertext. What I mean by fixed is that there is a set and limited number of symbols to represent the characters, numbers, and punctuations. In addition, they are usually the same (the plaintext symbols have the same and equivalent counterpart in the cyphertext symbols). Almost all the encryption algorithms rely on a predefined keyspace and length for the encryption/decription keys, and it is usually fixed (number of bits). In addition, the algorithms used by the encryptions are static. There is a predefined number of operatiors, and a predefined order (loops included) of operations. The algorithm stays the same, and the plaintext and cyphertext along with the key are churned through this cypherblock. Base Encryption does the opposite: It utilizes the novel concepts of base conversion, symbol remapping, and dynamic algorithms (dynamic operators and dynamic operations). Base Encryption solves the weakness in todays encryption schemes, namely... Fixed symbols (base) Fixed keylengths Fixed algorithms (fixed number of operations and operators) Unique features... Immune from plain-text-attacks. Immune from brute-force-attacks. Can utilize throwaway algorithms (as opposed to throw away keys). Plug-And-Play engine (other cyphers can be augmentated to it)

cs.CR↗