Publications by authors named "Shigeki Takeuchi"
Article Synopsis
- Linear optical transformations of single-photon inputs are crucial for advancing photonic quantum technologies, enabling the observation of nonclassical correlations through these states.
- The study demonstrates the creation of a two-photon three-mode non-Fock state, which shows unique quantum coherences that can't be achieved with classical Fock states.
- Experimental results detail the fidelity of this non-Fock state by analyzing conditional visibilities, offering valuable insights into the technological needs for harnessing nonclassical correlations in multiphoton quantum optics.
Article Synopsis
- - The research focuses on developing an efficient method for generating broadband, spatially separable photon pairs using a chirped quasi-phase matching (QPM) slab waveguide, which is significant for optical quantum applications.
- - The study shows that a 3% chirped QPM slab waveguide produces a much larger photon pair bandwidth (190 nm) compared to a non-chirped version (26 nm), along with higher photon pair generation efficiency.
- - The experiments confirmed successful two-photon interference, achieving a high visibility of 98% for the non-chirped device and 74% for the chirped device, demonstrating the effectiveness of slab waveguides in this context.
Article Synopsis
- Nanofiber Bragg cavities (NFBCs) are microcavities in optical fibers that can be adjusted to specific resonance wavelengths, crucial for aligning with single-photon emitters.
- The study examines how mechanical tension affects the NFBC's structure and optical properties, employing 3D simulations to understand its tunability and limitations.
- Results show that applying tension significantly alters the cavity's dimensions, shifting the resonance peak by 21.5 nm and impacting the quality factor (Q factor) of the cavity, which is essential for optimizing performance in photonic applications.
Article Synopsis
- - Infrared quantum absorption spectroscopy allows for analyzing the infrared properties of materials without the need for traditional infrared light sources or detectors, overcoming previous limitations in sensitivity and device size.
- - Previous experiments have focused on shorter wavelengths, but this study successfully demonstrates quantum Fourier-transform infrared (QFTIR) spectroscopy in the fingerprint region (1500-500 cm or 6.6 to 20 µm), which is crucial for identifying chemical compounds.
- - The research showcased obtaining precise transmittance spectra for materials like silicon and polytetrafluoroethylene, revealing specific absorption characteristics, thereby paving the way for advanced spectroscopy technologies using quantum methods.
Article Synopsis
- Quantum optical coherence tomography (QOCT) is a new method aimed at improving image resolution in optical coherence tomography (OCT), particularly when dealing with dispersion effects.
- An experimental study successfully demonstrated QOCT's capability to achieve a depth resolution of 2.5 micrometers, the highest reported so far for this technology.
- The results indicate that QOCT can produce clear images of dispersive materials, while traditional OCT images suffer from significant degradation.
Article Synopsis
- Solid-state quantum emitters paired with single mode fibers are crucial for advanced photonic and quantum technologies, with nanofibre Bragg cavities (NFBCs) emerging as effective coupling devices.
- The study introduces a hybrid device combining NFBCs with hexagonal boron nitride (hBN) nanoflakes, aiming to overcome the limitations of colloidal quantum dots due to photo-bleaching.
- The researchers successfully fabricated NFBCs with a high quality factor and resonant wavelength that aligns with hBN fluorescence, and they achieved notable emission results by exciting the nanoflakes and capturing the emitted light through the NFBC.
We present a highly efficient photon pair source using chirped quasi-phase-matched (QPM) devices with a ridge waveguide structure. We developed QPM waveguide devices with chirp rates of 3% and 6.7%.
View Article and Find Full Text PDFSome individuals can quickly acquire novel motor skills, while others take longer. This study aimed to investigate the relationships between neurophysiological state, sports experience, and novel ball-related skill acquisition. We enrolled 28 healthy collegiate participants.
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- Frequency entangled photon sources are crucial for various optical quantum technologies like quantum key distribution and quantum computation.
- Researchers developed a silicon nitride ring cavity to generate frequency correlated photon pairs at a rate of 150 GHz, demonstrating compatibility with existing tech.
- The study includes characterizing the phase matching condition, evaluating the joint spectrum intensity of 42 photon frequency pairs, and analyzing how these results relate to the phase matching condition.
We demonstrate room-temperature C hyperpolarization by dynamic nuclear polarization (DNP) using optically polarized triplet electron spins in two polycrystalline systems: pentacene-doped [carboxyl-C] benzoic acid and microdiamonds containing nitrogen-vacancy (NV) centers. For both samples, the integrated solid effect (ISE) is used to polarize the C spin system in magnetic fields of 350-400 mT. In the benzoic acid sample, the C spin polarization is enhanced by up to 0.
View Article and Find Full Text PDFA source to efficiently generate multiple indistinguishable single photons in different spatial modes in parallel (multi-photon parallel state) is indispensable for realizing large-scale photonic quantum circuits. "A naive scheme" may be to use a heralding single photon source with an on-off detector set at each of parallel modes and to select the cases where each mode contains one photon at the same time. However, it is also necessary to suppress the probability of generating more than two photons from a single-photon source.
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- The study focuses on improving light excitation methods for nitrogen-vacancy (NV) centers in nanodiamonds, important for quantum technologies, by using a nanofiber.
- The challenge is that background light from the nanofiber interferes with the emission light from the NV centers, complicating their detection.
- The authors propose a nanofiber Bragg cavity to significantly reduce the optical excitation intensity, potentially allowing for better fluorescence detection by decreasing the interference from background light.
Article Synopsis
- Nanofiber Bragg cavities (NFBCs) are advanced microcavities made from optical tapered fiber, showing great potential for photonic quantum information technology due to their small size and high efficiency.
- The existing NFBCs had a quality (Q) factor around 250, which is thought to be limited by the manufacturing process.
- A new method using a focused helium ion beam has achieved NFBCs with a Q factor exceeding 4170, more than 16 times higher than those made with a focused gallium ion beam.
The detection of nanoscale structure/material property in a wide observation area is becoming very important in various application fields. However, it is difficult to utilize current optical technologies. Toward the realization of novel alternative, we have investigated a new optical sensing method using an optical nanofiber.
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- The three-box paradox has progressed through three key developments: a non-counterfactual scheme using strong measurements (2003), a practical implementation by Okamoto and Takeuchi (2016), and a dynamic model that involves particle disappearance and reappearance (2017).
- The new experiment combines these advancements by employing photonic quantum routers, where a particle acts as a quantum "shutter," splitting its presence across three boxes.
- By tracking the particle's movements with a probe photon, the results show a certain time-evolution of the particle's location, while applying a Bell-like theorem to challenge alternative interpretations that rely on local hidden variables.
Article Synopsis
- * Our optimized devices achieved a 35.6% coupling efficiency while maintaining fiber transmission when cooled to 4.2 K, indicating effectiveness for low-temperature applications.
- * The research highlights the potential for creating advanced fiber-based quantum nanophotonic interfaces using diamond spin defect centers, which could enhance future quantum technologies.
Article Synopsis
- The use of three-qubit gates, specifically controlled-SWAP (Fredkin) gates, may enhance the structure and scalability of quantum circuits, crucial for protocols like error correction and optimal cloning.
- The study reports a successful realization of the Fredkin gate for photonic qubits, achieving a fidelity of 0.85 and indicating its potential for various quantum applications.
Heralded single-photon sources (HSPS) are widely used in experimental quantum science because they have negligibly small jitter and can therefore achieve high visibility for quantum interference. However, it is necessary to decrease the photon generation rate to suppress multi-photon components. To address this problem, two methods have been proposed and discussed: spatial (or temporal) source multiplexing and photon-pair number discrimination.
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- The phenomenon of single photon interference at a double slit is a key paradox in quantum theory, leading to questions about how a "quantum shutter" could operate.
- Aharonov and Vaidman proposed a method to create a quantum shutter that simultaneously closes two slits, which has now been experimentally demonstrated using photonic quantum routers.
- The experiment achieved a reflectance ratio of 0.61, exceeding classical limits, suggesting new insights into quantum operations and providing a different approach to study the nature of quantum physics.
We report on the coupling of single nitrogen vacancy (NV) centers to ultrathin fiber-taper nanofibers by the manipulation of single diamond nanocrystals on the nanofibers under real-time observation of nanodiamond fluorescence. Spin-dependent fluorescence of the single NV centers is efficiently detected through the nanofiber. We show control of the spin sub-level structure of the electronic ground state using an external magnetic field and clearly observe a frequency fine tuning of [Formula: see text].
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- This study numerically analyzes the coupling of a single dipole with a nanofiber Bragg cavity using three-dimensional simulations for various dipole positions.
- The results show that the Purcell factor and coupling efficiency are 19.1 and 82% respectively when the dipole is positioned outside the fiber, which are very close to the maximum values of 20.2 and 84% when the dipole is inside the fiber center.
- The findings aim to enhance the performance of quantum devices that utilize single-photon emitters and nanofiber Bragg cavities.
By means of an ultrafast optical technique, we track focused gigahertz coherent phonon pulses in objects down to sub-micron in size. Infrared light pulses illuminating the surface of a single metal-coated silica fibre generate longitudinal-phonon wave packets. Reflection of visible probe light pulses from the fibre surface allows the vibrational modes of the fibre to be detected, and Brillouin optical scattering of partially transmitted light pulses allows the acoustic wavefronts inside the transparent fibre to be continuously monitored.
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- Understanding how we perceive the timing of sensory events is crucial for navigating dynamic environments, and studies often compare two methods: temporal order judgement (TOJ) and simultaneity judgement (SJ).
- Although TOJ and SJ have similar metrics, emerging evidence indicates they involve distinct perceptual processes, with TOJ requiring more complex cognitive operations.
- Brain imaging showed that TOJ activates specific regions in the premotor and parietal cortices, while SJ primarily engages the posterior insular cortex, supporting the idea that these two judgements rely on different neural mechanisms.
We report the measurements of charge density of tapered optical fibers using charged particles confined in a linear Paul trap at ambient pressure. A tapered optical fiber is placed across the trap axis at a right angle, and polystyrene microparticles are trapped along the trap axis. The distance between the equilibrium position of a positively charged particle and the tapered fiber is used to estimate the amount of charge per unit length of the fiber without knowing the amount of charge of the trapped particle.
View Article and Find Full Text PDFPhotonic quantum information: science and technology.
Proc Jpn Acad Ser B Phys Biol Sci
October 2016
Article Synopsis
- Recent advancements in technology have enabled the generation, manipulation, and detection of single photons, leading to a new area of study known as photonic quantum information.
- Key innovations include the creation of single photon switches and specialized photonic quantum circuits, as well as the use of unique photonic states for advanced optical measurement techniques.
- The review article discusses these developments and assesses the current state of photonic quantum information technology, drawing from the author’s previous and recent research.