arXiv subjects

Makoto Takeuchi

Publications and source records attributed to Makoto Takeuchi.

12 recordsLinked to original sources

arXiv2026

Two-Dimensional Structural Characterization of Music Genre Communities in Playlist Co-occurrence Networks

Music genre classification shapes how listeners discover music, how platforms design recommendations, and how sociologists study cultural taste. Yet existing genre labels are inconsistent in granularity: they exaggerate boundaries between overlapping categories and hide sociologically important heterogeneity within broad labels. Cultural sociologists have long theorized that genres vary along two independent dimensions, boundary strength and internal differentiation, but existing empirical work has relied on fixed label sets, leaving these dimensions without quantitative operationalization from actual consumption behavior data. Here we propose a two-dimensional framework that extracts music communities bottom-up from playlist co-occurrence networks and characterizes each along two axes: external closure $B(C)$, measuring boundary strength relative to a random null, and internal differentiation $D(C)$, measuring organized internal subdivision. We validate the framework on two independent datasets across platforms, cultural contexts, and time periods, confirming that $B(C)$ and $D(C)$ are statistically independent and that each captures a distinct structural property. The framework reveals genre structures invisible to fixed labels: single labels splitting into communities with different boundary strengths, multiple labels merging into tightly bounded communities, and consumption spheres that no existing label describes. Comparison with prior theoretical predictions is broadly consistent, with the notable exception that Hip-Hop exhibits rich internal differentiation across both datasets, challenging its prevailing single-centered characterization. By providing a label-independent coordinate system grounded in listener behavior, this framework opens a path toward tracking how genre boundaries and internal structures evolve over time, a question that static label systems cannot address.

physics.soc-ph↗

arXiv2024

Phase noise measurement by zero-crossing analysis with a double recorder setup in the radiofrequency range

The phase noise of low-noise oscillators is conventionally measured by the cross-spectrum method (CSM), which has a complicated setup. We developed an alternative method called zero-crossing analysis with a double recorder setup (ZCA-DRS) that has much simpler configuration, which we previously demonstrated to measure phase noise in the audible frequency range. In this study we conducted experiments using ZCA-DRS to measure phase noise in the radiofrequency range. A temperature-compensated crystal oscillator was used to generate a periodic signal at 27 MHz. The results demonstrated that the obtained single-side band spectrum was almost the same as that obtained by CSM. The measurement sensitivity was limited by the jitter of the internal clock and noise of the analog-to-digital converter. Thus, ZCA-DRS can be used as an alternative to CSM for phase noise measurement in the radiofrequency range.

physics.ins-det↗

arXiv2023

A method for analyzing sampling jitter in audio equipment

A method for analyzing sampling jitter in audio equipment is proposed. The method is based on the time-domain analysis where the time fluctuations of zero-crossing points in recorded sinusoidal waves are employed to characterize jitter. This method enables the separate evaluation of jitter in an audio player from those in audio recorders when the same playback signal is simultaneously fed into two audio recorders. Experiments are conducted using commercially available portable devices with a maximum sampling rate of 192~000 samples per second. The results show jitter values of a few tens of picoseconds can be identified in an audio player. Moreover, the proposed method enables the separation of jitter from phase-independent noise utilizing the left and right channels of the audio equipment. As such, this method is applicable for performance evaluation of audio equipment, signal generators, and clock sources.

cs.SD↗

arXiv2022

Burstiness of human physical activities and their characterization

Human behaviour is heterogeneous and temporally fluctuates. Many studies have focused on inter-event time (IET) fluctuations and have reported that the IET distributions have a long-tailed distribution, which cannot be explained by a stationary Poisson point process. Such phenomenon observed in IET distributions are known as burstiness. Burstiness has also been reported for human physical activity, but the mechanism underlying it has not been clarified. In this study, we collected human physical activity data while specifying the age of the subjects and their situations (for example, children's play and adults' housework), and we analysed their event time-series data. We confirmed the burstiness in both children and adults. For the first time, burstiness studied in physical activities of children between the ages 2 and 5. We also confirmed that the characteristics of the IET distribution are unique to each activity situation. Our results may be critical in the identification of the burstiness mechanisms in human physical activity.

physics.soc-ph↗

arXiv2013

Photoionization loss in simultaneous magneto-optical trapping of Rb and Sr

We demonstrate the simultaneous magneto-optical trapping (MOT) of Rb and Sr and examine the characteristic loss of Rb in the MOT due to photoionization by the cooling laser for Sr. The photoionization cross section of Rb in the $5P_{3/2}$ state at 461 nm is determined to be $1.4(1)\times10^{-17}$ cm$^2$. It is important to consider this loss rate to realize a sufficiently large number of trapped Rb atoms to achieve a quantum degenerate mixture of Rb and Sr.

physics.atom-ph↗

arXiv2013

Continuous-variable qubit on an optical transverse mode

Continuous-variable (CV) qubits can be created on an optical longitudinal mode in which quantum information is encoded by the superposition of even and odd Schroedinger's cat states with quadrature amplitude. Based on the analogous features of paraxial optics and quantum mechanics, we propose a system to generate and detect CV qubits on an optical transverse mode. As a proof-of-principle experiment, we generate six CV qubit states and observe their probability distributions in position and momentum space. This enabled us to prepare a non-Gaussian initial state for CV quantum computing. Other potential applications of the CV qubit include adiabatic control of a beam profile, phase shift keying on transverse modes, and quantum cryptography using CV qubit states.

quant-ph↗

arXiv2012

Locking Local Oscillator Phase to the Atomic Phase via Weak Measurement

We propose a new method to reduce the frequency noise of a Local Oscillator (LO) to the level of white phase noise by maintaining (not destroying by projective measurement) the coherence of the ensemble pseudo-spin of atoms over many measurement cycles. This scheme uses weak measurement to monitor the phase in Ramsey method and repeat the cycle without initialization of phase and we call, "atomic phase lock (APL)" in this paper. APL will achieve white phase noise as long as the noise accumulated during dead time and the decoherence are smaller than the measurement noise. A numerical simulation confirms that with APL, Allan deviation is averaged down at a maximum rate that is proportional to the inverse of total measurement time, tau^-1. In contrast, the current atomic clocks that use projection measurement suppress the noise only down to the level of white frequency, in which case Allan deviation scales as tau^-1/2. Faraday rotation is one of the possible ways to realize weak measurement for APL. We evaluate the strength of Faraday rotation with 171Yb+ ions trapped in a linear rf-trap and discuss the performance of APL. The main source of the decoherence is a spontaneous emission induced by the probe beam for Faraday rotation measurement. One can repeat the Faraday rotation measurement until the decoherence become comparable to the SNR of measurement. We estimate this number of cycles to be ~100 cycles for a realistic experimental parameter.

physics.atom-ph↗

arXiv2011

Photon subtraction from traveling fields - recent experimental demonstrations

We review our most recent results on application of the photon subtraction technique for optical quantum information processing primitives, in particular entanglement distillation and generation of squeezed qubit states. As an introduction we provide a brief summary of other experimental accomplishments in the field.

quant-ph↗

arXiv2010

Faraday Rotation with Single Nuclear Spin Qubit in a High-Finesse Optical Cavity

When an off-resonant light field is coupled with atomic spins, its polarization can rotate depending on the direction of the spins via a Faraday rotation which has been used for monitoring and controlling the atomic spins. We observed Faraday rotation by an angle of more than 10 degrees for a single 1/2 nuclear spin of 171Yb atom in a high-finesse optical cavity. By employing the coupling between the single nuclear spin and a photon, we have also demonstrated that the spin can be projected or weakly measured through the projection of the transmitted single ancillary photon.

quant-ph↗

arXiv2010

Single Nuclear Spin Cavity QED

We constructed a cavity QED system with a diamagnetic atom of 171Yb and performed projective measurements on a single nuclear spin. Since Yb has no electronic spin and has 1/2 nuclear spin, the procedure of spin polarization and state verification can be dramatically simplified compared with the pseudo spin-1/2 system. By enhancing the photon emission rate of the 1S0-3P1 transition, projective measurement is implemented for an atom with the measurement time of T_meas = 30us. Unwanted spin flip as well as dark counts of the detector lead to systematic error when the present technique is applied for the determination of diagonal elements of an unknown spin state, which is delta|beta|^2 < 2 * 10^-2. Fast measurement on a long-lived qubit is key to the realization of large-scale one-way quantum computing.

quant-ph↗

arXiv2010

Optical continuous-variable qubit

In a new branch of quantum computing, information is encoded into coherent states, the primary carriers of optical communication. To exploit it, quantum bits of these coherent states are needed, but it is notoriously hard to make superpositions of such continuous-variable states. We have realized the complete engineering and characterization of a qubit of two optical continuous-variable states. Using squeezed vacuum as a resource and a special photon subtraction technique, we could with high precision prepare an arbitrary superposition of squeezed vacuum and a squeezed single photon. This could lead the way to demonstrations of coherent state quantum computing.

quant-ph↗

arXiv2009

Non-Gaussian entanglement distillation for continuous variables

Entanglement distillation is an essential ingredient for long distance quantum communications. In the continuous variable setting, Gaussian states play major roles in quantum teleportation, quantum cloning and quantum cryptography. However, entanglement distillation from Gaussian states has not yet been demonstrated. It is made difficult by the no-go theorem stating that no Gaussian operation can distill Gaussian states. Here we demonstrate the entanglement distillation from Gaussian states by using measurement-induced non-Gaussian operations, circumventing the fundamental restriction of the no-go theorem. We observed a gain of entanglement as a result of conditional local subtraction of a single photon or two photons from a two-mode Gaussian state. Furthermore we confirmed that two-photon subtraction also improves Gaussian-like entanglement as specified by the Einstein-Podolsky-Rosen (EPR) correlation. This distilled entanglement can be further employed to downstream applications such as high fidelity quantum teleportation and a loophole-free Bell test.

quant-ph↗