arXiv subjects

Sumito Yokoo

Publications and source records attributed to Sumito Yokoo.

3 recordsLinked to original sources

arXiv2020

Revisiting weak measurement in light of thermodynamics

We investigate a weak measurement described by a von Neumann type interaction $\hat{A}\otimes \hat{p}^2$, where $\hat{A}$ is a system observable and $\hat{p}^2$ is a measurement pointer observable. We consider the weak measurement in terms of thermodynamics by adopting a mixed Gaussian state as a quantum state of the measurement pointer. We show that Maxwell's demon appears as a measure who carries out post-selections. It is found that, even if the demon only knows the weak value, a difference in the von Neumann entropy between the initial and final system can be the QC mutual information contents, which is the maximum amount of obtainable information by a measurement. Besides, our study indicates that a temperature of the system described by this interaction is amplified by weak value amplification. In addition, we show that this demon can be realized in an atomic system.

cond-mat.stat-mech↗

arXiv2018

Scale-invariant Feature Extraction of Neural Network and Renormalization Group Flow

Theoretical understanding of how deep neural network (DNN) extracts features from input images is still unclear, but it is widely believed that the extraction is performed hierarchically through a process of coarse-graining. It reminds us of the basic concept of renormalization group (RG) in statistical physics. In order to explore possible relations between DNN and RG, we use the Restricted Boltzmann machine (RBM) applied to Ising model and construct a flow of model parameters (in particular, temperature) generated by the RBM. We show that the unsupervised RBM trained by spin configurations at various temperatures from $T=0$ to $T=6$ generates a flow along which the temperature approaches the critical value $T_c=2.27$. This behavior is opposite to the typical RG flow of the Ising model. By analyzing various properties of the weight matrices of the trained RBM, we discuss why it flows towards $T_c$ and how the RBM learns to extract features of spin configurations.

hep-th↗

arXiv2017

Electromagnetic Radiation in a Semi-Compact Space

In this note, we investigate the electromagnetic radiation emitted from a revolving point charge in a compact space. If the point charge is circulating with an angular frequency $ω_0$ on the $(x,y)$-plane at $z=0$ with boundary conditions, $x \sim x+2 πR$ and $y \sim y+2πR$, it emits radiation into the $z$-direction of $z$ in $ [-\infty, +\infty]$. We find that the radiation shows discontinuities as a function of $ω_0 R$ at which a new propagating mode with a different Fourier component appears. For a small radius limit $ω_0 R \ll 1$, all the Fourier modes except the zero mode on $(x,y)$-plane are killed, but an effect of squeezing the electric field totally enhances the radiation. In the large volume limit $ω_0 R \rightarrow \infty$, the energy flux of the radiation reduces to the expected Larmor formula.

hep-th↗