arXiv subjects

Hiroyasu Tajima

Publications and source records attributed to Hiroyasu Tajima.

At least 73 records · Page 4Linked to original sources

arXiv2017

Large Deviation implies First and Second Laws of Thermodynamics

To reconstruct thermodynamics based on the microscopic laws is one of the most important unfulfilled goals of statistical physics. Here, we show that the first law and the second law for adiabatic processes are derived from an assumption that "probability distributions of energy in Gibbs states satisfy large deviation", which is widely accepted as a property of thermodynamic equilibrium states. We define an adiabatic transformation as a randomized energy-preserving unitary transformations on the many-body systems and the work storage. As the second law, we show that an adiabatic transformation from a set of Gibbs states to another set of Gibbs states is possible if and only if the regularized von Neumann entropy becomes large. As the first law, we show that the energy loss of the thermodynamic systems during the adiabatic transformation is stored in the work storage as "work," in the following meaning; (i) the energy of the work storage takes certain values macroscopically, in the initial state and the final state. (ii) the entropy of the work storage in the final state is macroscopically equal to the entropy of the initial state. As corollaries, our results give the principle of maximam work and the first law for the isothermal processes.

quant-ph↗

arXiv2017

Measurement-based Formulation of Quantum Heat Engine

There exist two formulations for quantum heat engine that models an energy transfer between two microscopic systems. One is semi-classical scenario, and the other is full quantum scenario. The former is formulated as a unitary evolution for the internal system, and is adopted by the community of statistical mechanics. In the latter, the whole process is formulated as unitary, and is adopted by the community of quantum information. This paper proposes a model for quantum heat engine that transfers energy from a collection of microscopic systems to a macroscopic system like a fuel cell. In such a situation, the amount of extracted work is visible for a human. For this purpose, we formulate quantum heat engine as the measurement process whose measurement outcome is the amount of extracted work. Under this model, we derive a suitable energy conservation law and propose a more concrete submodel. Then, we derive a novel trade-off relation between the measurability of the amount of work extraction and the coherence of the internal system, which examines the application of the semi-classical scenario to a heat engine transferring an energy from a collection of microscopic systems to a macroscopic system.

quant-ph↗

arXiv2016

Quantum Jarzynski equality of measurement-based work extraction

Many studies of quantum-size heat engines assume that the dynamics of an internal system is unitary and that the extracted work is equal to the energy loss of the internal system. Both assumptions, however, should be under scrutiny. In the present paper, we analyze quantum-scale heat engines, employing the measurement-based formulation of the work extraction recently introduced by Hayashi and Tajima~[arXiv:1504.06150]. We first demonstrate the inappropriateness of the unitary time evolution of the internal system (namely the first assumption above) using a simple two-level system; we show that the variance of the energy transferred to an external system diverges when the dynamics of the internal system is approximated to a unitary time evolution. We second derive the quantum Jarzynski equality based on the formulation of Hayashi and Tajima as a relation for the work measured by an external macroscopic apparatus. The right-hand side of the equality reduces to unity for "natural" cyclic processes, but fluctuates wildly for non-cyclic ones, exceeding unity often. This fluctuation should be detectable in experiments and provide evidence for the present formulation.

cond-mat.stat-mech↗

arXiv2016

Study of the Polarimetric Performance of a Si/CdTe Semiconductor Compton Camera for the Hitomi Satellite

Gamma-ray polarization offers a unique probes into the geometry of the gamma-ray emission process in celestial objects. The Soft Gamma-ray Detector (SGD) onboard the X-ray observatory Hitomi is a Si/CdTe Compton camera and is expected to be an excellent polarimeter, as well as a highly sensitive spectrometer due to its good angular coverage and resolution for Compton scattering. A beam test of the final-prototype for the SGD Compton camera was conducted to demonstrate its polarimetric capability and to verify and calibrate the Monte Carlo simulation of the instrument. The modulation factor of the SGD prototype camera, evaluated for the inner and outer parts of the CdTe sensors as absorbers, was measured to be 0.649--0.701 (inner part) and 0.637--0.653 (outer part) at 122.2 keV and 0.610--0.651 (inner part) and 0.564--0.592 (outer part) at 194.5 keV at varying polarization angles with respect to the detector. This indicates that the relative systematic uncertainty of the modulation factor is as small as ~3%.

astro-ph.IM↗

arXiv2016

Regularized Boltzmann entropy determines macroscopic adiabatic accessibility

How the thermodynamic entropy $S_{TD}$ is related to the Boltzmann entropy $S_{B}$ has been one of the central issues since the beginning of statistical mechanics. Today, it is believed that the thermodynamic entropy $S_{TD}$ is equal to a function $\tilde{S}_{B}$ that is defined by regularizing the Boltzman entropy in order to ensure extensivity. However, it is not known whether $\tilde{S}_{B}$ completely determines the possibility of a macroscopic adiabatic transformation in the same way as $S_{TD}$ does. In this paper, by formulating the possibility of a macroscopic adiabatic transformations in terms of "coarse-graining" of quantum operations, we prove that $\tilde{S}_{B}$ provides a necessary and sufficient condition for the possibility of a macroscopic adiabatic transformation.

quant-ph↗

arXiv2016

Optimal Efficiency of Heat Engines with Finite-Size Heat Baths

The optimal efficiency of quantum (or classical) heat engines whose heat baths are $n$-particle systems is given by the information geometry and the strong large deviation. We give the optimal work extraction process as a concrete energy-preserving unitary time evolution among the heat baths and the work storage. We show that our optimal work extraction turns the disordered energy of the heat baths to the ordered energy of the work storage, by evaluating the ratio of the entropy difference to the energy difference in the heat baths and the work storage, respectively. By comparing the statistical mechanical optimal efficiency with the macroscopic thermodynamic bound, we evaluate the accuracy of the macroscopic thermodynamics with finite-size heat baths from the statistical mechanical viewpoint. We also evaluate the quantum coherence effect on the optimal efficiency of the cycle processes without restricting their cycle time, by comparing the classical and quantum optimal efficiencies.

quant-ph↗

arXiv2015

The first demonstration of the concept of "narrow-FOV Si/CdTe semiconductor Compton camera"

The Soft Gamma-ray Detector (SGD), to be deployed onboard the {\it ASTRO-H} satellite, has been developed to provide the highest sensitivity observations of celestial sources in the energy band of 60-600~keV by employing a detector concept which uses a Compton camera whose field-of-view is restricted by a BGO shield to a few degree (narrow-FOV Compton camera). In this concept, the background from outside the FOV can be heavily suppressed by constraining the incident direction of the gamma ray reconstructed by the Compton camera to be consistent with the narrow FOV. We, for the first time, demonstrate the validity of the concept using background data taken during the thermal vacuum test and the low-temperature environment test of the flight model of SGD on ground. We show that the measured background level is suppressed to less than 10\% by combining the event rejection using the anti-coincidence trigger of the active BGO shield and by using Compton event reconstruction techniques. More than 75\% of the signals from the field-of-view are retained against the background rejection, which clearly demonstrates the improvement of signal-to-noise ratio. The estimated effective area of 22.8~cm$^2$ meets the mission requirement even though not all of the operational parameters of the instrument have been fully optimized yet.

astro-ph.IM↗

arXiv2015

Fine-pitch semiconductor detector for the FOXSI mission

The Focusing Optics X-ray Solar Imager (FOXSI) is a NASA sounding rocket mission which will study particle acceleration and coronal heating on the Sun through high sensitivity observations in the hard X-ray energy band (5-15 keV). Combining high-resolution focusing X-ray optics and fine-pitch imaging sensors, FOXSI will achieve superior sensitivity; two orders of magnitude better than that of the RHESSI satellite. As the focal plane detector, a Double-sided Si Strip Detector (DSSD) with a front-end ASIC (Application Specific Integrated Circuit) will fulfill the scientific requirements of spatial and energy resolution, low energy threshold and time resolution. We have designed and fabricated a DSSD with a thickness of 500 μm and a dimension of 9.6 mm x 9.6 mm, containing 128 strips with a pitch of 75 μm, which corresponds to 8 arcsec at the focal length of 2 m. We also developed a low-noise ASIC specified to FOXSI. The detector was successfully operated in the laboratory at a temperature of -20 C and with an applied bias voltage of 300 V, and the energy resolution of 430 eV at a 14 keV line was achieved. We also demonstrated fine-pitch imaging successfully by obtaining a shadow image, hence the implementation of scientific requirements was confirmed.

astro-ph.IM↗

arXiv2015

The Si/CdTe semiconductor Compton camera of the ASTRO-H Soft Gamma-ray Detector (SGD)

The Soft Gamma-ray Detector (SGD) is one of the instrument payloads onboard ASTRO-H, and will cover a wide energy band (60--600 keV) at a background level 10 times better than instruments currently in orbit. The SGD achieves low background by combining a Compton camera scheme with a narrow field-of-view active shield. The Compton camera in the SGD is realized as a hybrid semiconductor detector system which consists of silicon and cadmium telluride (CdTe) sensors. The design of the SGD Compton camera has been finalized and the final prototype, which has the same configuration as the flight model, has been fabricated for performance evaluation. The Compton camera has overall dimensions of 12 cm x 12 cm x 12 cm, consisting of 32 layers of Si pixel sensors and 8 layers of CdTe pixel sensors surrounded by 2 layers of CdTe pixel sensors. The detection efficiency of the Compton camera reaches about 15% and 3% for 100 keV and 511 keV gamma rays, respectively. The pixel pitch of the Si and CdTe sensors is 3.2 mm, and the signals from all 13312 pixels are processed by 208 ASICs developed for the SGD. Good energy resolution is afforded by semiconductor sensors and low noise ASICs, and the obtained energy resolutions with the prototype Si and CdTe pixel sensors are 1.0--2.0 keV (FWHM) at 60 keV and 1.6--2.5 keV (FWHM) at 122 keV, respectively. This results in good background rejection capability due to better constraints on Compton kinematics. Compton camera energy resolutions achieved with the final prototype are 6.3 keV (FWHM) at 356 keV and 10.5 keV (FWHM) at 662 keV, respectively, which satisfy the instrument requirements for the SGD Compton camera (better than 2%). Moreover, a low intrinsic background has been confirmed by the background measurement with the final prototype.

astro-ph.IM↗

arXiv2013

Quantum Jarzynski equalities for the energy costs of the information processes

We present quantum versions of the Jarzynski equality for the energy costs of information processes, namely the measurement and the information erasure. We also obtain inequalities for the energy costs of the information processes, using the Jensen inequality. The inequalities include Sagawa and Ueda's inequalities [Phys. Rev. Lett. 102, 250602 (2009)] as a special case.

cond-mat.stat-mech↗

arXiv2013

Minimal energy cost of thermodynamic information processes only with entanglement transfer

We present the minimal energy costs for the measurement and the information erase, using only the Helmholtz free energy and the entanglement of formation. The entanglement of formation appears in the form of difference which indicates the amount of entanglement transfer on the memory during the processes; the cost of the measurement is given by the entanglement gain, whereas the cost of the information erase is given by the loss of available entanglement. Putting together the present Letter and Rev. E 88, 042143 (2013), we can describe the violation and the restoration of the second law only in terms of the entanglement of formation; both of the excess of extracted work from thermodynamics with information process over the conventional second law and the total cost of the information process are given by the entanglement of formation, and the former is less than or equal to the latter.

quant-ph↗

arXiv2013

Analytically computable tangle for three-qubit mixed states

We present a new tripartite entanglement measure for three-qubit mixed states. The new measure $t_{\mathrm{r}}(ρ)$, which we refer to as the r-tangle, is given as a kind of the tangle, but has a feature which the tangle does not have; if we can derive an analytical form of $ t_{\mathrm{r}}(ρ)$ for a three-qubit mixed state $ρ$, we can also derive $t_{\mathrm{r}}(ρ')$ analytically for any states $ρ'$ which are SLOCC-equivalent to the state $ρ$. The concurrence of two-qubit states also satisfies the feature, but the tangle does not. These facts imply that the r-tangle $t_{\mathrm{r}}$ is the appropriate three-partite counterpart of the concurrence. We also derive an analytical form of the r-tangle $t_{\mathrm{r}}$ for mixtures of a generalized GHZ state and a generalized W state, and hence for all states which are SLOCC-equivalent to them.

quant-ph↗

arXiv2013

Photosensor Characterization for the Cherenkov Telescope Array: Silicon Photomultiplier versus Multi-Anode Photomultiplier Tube

Photomultiplier tube technology has been the photodetector of choice for the technique of imaging atmospheric Cherenkov telescopes since its birth more than 50 years ago. Recently, new types of photosensors are being contemplated for the next generation Cherenkov Telescope Array. It is envisioned that the array will be partly composed of telescopes using a Schwarzschild-Couder two mirror design never built before which has significantly improved optics. The camera of this novel optical design has a small plate scale which enables the use of compact photosensors. We present an extensive and detailed study of the two most promising devices being considered for this telescope design: the silicon photomultiplier and the multi-anode photomultiplier tube. We evaluated their most critical performance characteristics for imaging gamma-ray showers, and we present our results in a cohesive manner to clearly evaluate the advantages and disadvantages that both types of device have to offer in the context of GeV-TeV gamma-ray astronomy.

astro-ph.IM↗

arXiv2013

Second law of the information thermodynamics with entanglement transfer

We present a new inequality which holds in the thermodynamical processes with measurement and feedback controls with using only the Helmholtz free energy and the entanglement of formation: $W_{\mathrm{ext}}\le-ΔF-k_{B}TΔE_{F}$. The quantity $-ΔE_{F}$, which is positive, expresses the amount of entanglement transfer from the system $S$ to the probe $P$ through the interaction $\hat{U}_{SP}$ during the measurement. It is easier to achieve the upper bound in the new inequality than in the Sagawa-Ueda inequality [Phys. Rev. Lett. 100 080403 (2008)]. The new inequality has clear physical meaning: in the above thermodynamical processes, the work which we can extract from the thermodynamic system is greater than the upper bound in the conventional thermodynamics by the amount of the entanglement extracted by the measurement.

quant-ph↗

arXiv2013

Gamma-Ray Burst Science in the Era of the Cherenkov Telescope Array

We outline the science prospects for gamma-ray bursts (GRBs) with the Cherenkov Telescope Array (CTA), the next-generation ground-based gamma-ray observatory operating at energies above few tens of GeV. With its low energy threshold, large effective area and rapid slewing capabilities, CTA will be able to measure the spectra and variability of GRBs at multi-GeV energies with unprecedented photon statistics, and thereby break new ground in elucidating the physics of GRBs, which is still poorly understood. Such measurements will also provide crucial diagnostics of ultra-high-energy cosmic ray and neutrino production in GRBs, advance observational cosmology by probing the high-redshift extragalactic background light and intergalactic magnetic fields, and contribute to fundamental physics by testing Lorentz invariance violation with high precision. Aiming to quantify these goals, we present some simulated observations of GRB spectra and light curves, together with estimates of their detection rates with CTA. Although the expected detection rate is modest, of order a few GRBs per year, hundreds or more high-energy photons per burst may be attainable once they are detected. We also address various issues related to following up alerts from satellites and other facilities with CTA, as well as follow-up observations at other wavelengths. The possibility of discovering and observing GRBs from their onset including short GRBs during a wide-field survey mode is also briefly discussed.

astro-ph.HE↗

arXiv2012

Deterministic LOCC transformation of three-qubit pure states and entanglement transfer

A necessary and sufficient condition of the possibility of a deterministic local operations and classical communication (LOCC) transformation of three-qubit pure states is given. The condition shows that the three-qubit pure states are a partially ordered set parametrized by five well-known entanglement parameters and a novel parameter; the five are the concurrences $C_{AB}$, $C_{AC}$, $C_{BC}$, the tangle $τ_{ABC}$ and the fifth parameter $J_{5}$ of Ref. [18], while the other new one is the entanglement charge $Q_{e}$. The order of the partially ordered set is defined by the possibility of a deterministic LOCC transformation from a state to another state. In this sense, the present condition is an extension of Nielsen's work [20] to three-qubit pure states. We also clarify the rules of transfer and dissipation of the entanglement which is caused by deterministic LOCC transformations. Moreover, the minimum number of times of measurements to reproduce an arbitrary deterministic LOCC transformation between three-qubit pure states is given.

quant-ph↗

arXiv2012

Fermi-LAT Observation of Supernova Remnant S147

We present an analysis of gamma-ray data obtained with the Large Area Telescope (LAT) onboard the Fermi Gamma-ray Space Telescope in the region around SNR S147 (G180.0-1.7). A spatially extended gamma-ray source detected in an energy range of 0.2--10 GeV is found to coincide with SNR S147. We confirm its spatial extension at >5sigma confidence level. The gamma-ray flux is (3.8 \pm 0.6) x 10^{-8} photons cm^{-2} s^{-1}, corresponding to a luminosity of 1.3 x 10^{34} (d/1.3 kpc)^2 erg s^{-1} in this energy range. The gamma-ray emission exhibits a possible spatial correlation with prominent Halpha filaments of S147. There is no indication that the gamma-ray emission comes from the associated pulsar PSR J0538+2817. The gamma-ray spectrum integrated over the remnant is likely dominated by the decay of neutral pi mesons produced through the proton--proton collisions in the filaments. Reacceleration of pre-existing CRs and subsequent adiabatic compression in the filaments is sufficient to provide the required energy density of high-energy protons.

astro-ph.HE↗

arXiv2012

Fermi-LAT Discovery of GeV Gamma-ray Emission from the Vicinity of SNR W44

We report the detection of GeV gamma-ray emission from the molecular cloud complex that surrounds the supernova remnant (SNR) W44 using the Large Area Telescope (LAT) onboard Fermi. While the previously reported gamma-ray emission from SNR W44 is likely to arise from the dense radio-emitting filaments within the remnant, the gamma-ray emission that appears to come from the surrounding molecular cloud complex can be ascribed to the cosmic rays (CRs) that have escaped from W44. The non-detection of synchrotron radio emission associated with the molecular cloud complex suggests the decay of neutral pi mesons produced in hadronic collisions as the gamma-ray emission mechanism. The total kinetic energy channeled into the escaping CRs is estimated to be (0.3--3)x10^{50} erg, in broad agreement with the conjecture that SNRs are the main sources of Galactic CRs.

astro-ph.HE↗