Kouichi Toyoshima

Dependence of an LED Noise on Current Source Impedance

Photocurrent noise from an LED is measured as a function of the current source impedance. Bandwidth of noise reduction is found to be equal to the inverse of the time constant which is the product of the differential resistance of the LED and a paralelly connected capacitance. The experimental results are described in terms of a simple equivalent circuit.

Interference between different photons from two incoherent sources

Abstract Intensity interference fringes are observed by using two incoherent light-emitting diodes. It is verified that even an incoherent light interferes with another one.

Ballistic Quantum Walk in a Discrete One-Dimensional System

A continuous-time quantum walk in a one-dimensional discrete system is considered. There are interactions \(\hbar v/\Delta x\) between adjacent sites, where Δ x denotes the lattice spacing. If the initial state is spread over N sites, the packet travels ballistically with velocity v for N ≫1.

Anticorrelated noise from parallely connected light emitting diodes

Two LEDs (light emitting diodes) were drived by a constant-current source. Photocurrents from the two LEDs were measured and found to be anticorrelated owing to the shot-noise suppression due to the high impedance of the source. The correlations of the photocurrents are explained by a simple equivalent circuit.

Ballistic Quantum Walk of a Phase-Modulated Wave Packet

A continuous-time quantum walk of a phase-modulated wave packet is considered in a one-dimensional equispacing lattice {| k >| k ∈ Z }. The interaction \(\hbar c/\Delta x\) between adjacent sites drives the packet unidirectionally, where Δ x denotes the lattice spacing. If the initial state is spread over N consecutive sites and phase-modulated by exp (i k θ), the packet travels ballistically with a velocity v = (1 - N -1 ) c cos θ.

Noise Generation due to Time Delay Circuits

A quiet current with subshot noise is a regulated electron flow. When a time delay circuit, i.e. a low-pass filter is inserted into the flow, noise is generated in the high frequency region. By using a transistor circuit the noise generation due to the time delay is observed. A simple theoretical model explains the observed noise spectrum.

A coincidence counting system for a high count rate and very small true-to-accidental ratio

Abstract We have developed a special coincidence counting system which makes it possible to detect very rare coincident (or anticoincident) events under high accidental counting conditions. High differential uniformity which cannot be achieved by the ordinary TAC or TDC system was obtained. This system was designed to observe an intensity interference effect of an electron beam due to the quantum-mechanical nature of Fermi–Dirac statistics of electrons.

Study of diamond synthesized by simple hot-filament-assisted CVD in various conditions

Abstract We have attempted to synthesize diamonds on substrates using the simple hot-filament-assisted chemical vapour deposition (CVD) system reported by Hirose et al. (42nd Spring Meeting of Japan Society of Applied Physics and Related Societies, 1995, Extended Abstract, p. 374). Diamonds are synthesized, close to atmospheric pressure, from methanol without hydrogen gas in Hiroses CVD system. In this paper, we report the dependence of crystal growth on the bias voltage and distance between the filament and the substrate. No crystal growth can be observed for synthesis with a negative bias voltage. Different stages of crystal growth, which seem to occur due to the temperature gradient on the substrate, are observed on the same substrate for synthesis with a large distance between the filament and the substrate.

Interference between two incoherent lights

The noise of two incoherent lights was measured. The detected noise increased when one light source was set close to the other. This means that the two close light sources seem to tend to emit photons simultaneously in spite of their mutual incoherence and independence.

Loss in an Infinite Transmission Line

An infinitely long transmission line appears to have an ohmic conductance even when loss in circuit elements approaches zero. We show that the real part of the admittance of the transmission line derives from a dense distribution of resonance absorption lines.