We constructed a gamma-ray detector by combining two types of scintillator array detectors with an MPPC array and evaluated the spectral performance by reading out the signals from the MPPC with a low-power integrated circuit (ASIC) manufactured by I
DEAS in Norway. One of the two types of scintillators is a GAGG(Ce) (Ce-doped $ rm{Gd_3Al_2Ga_3O_{12}}$) scintillator, and the other is an LFS scintillator. The scintillator array is 2.5 cm $times$ 2.5 cm in size and is coated with $ rm{BaSO_4}$-based white paint for GAGG(Ce) and an enhanced specular reflector (ESR) for LFS except for the side optically coupled to the MPPC. The spectra derived from the array are affected by the MPPC photon saturations and light leakage from the adjacent pixels, and we carefully corrected for both effects in our data analysis. The energy resolution of 662 keV at 20 $^circ$C is 6.10$pm$0.04% for the GAGG(Ce) scintillator array and 8.57$pm$0.15% for the LFS scintillator array, this is equivalent to the typical energy resolution found in the references. The energy resolution depends on the temperature: the energy resolution improves as the temperature decreases. We found that the contribution of thermal noise from the MPPCs to the energy resolution is negligible within the range of --20 to 40 $^circ$C, and the energy resolution is mainly determined by the light yield of the crystals.
Quantum information is scrambled via chaotic time evolution in many-body systems. Recovering the scrambled information is crucial in todays physics, such as quantum chaos, quantum computers and the black hole information paradox. In realistic setting
s, symmetry can ubiquitously exist in scrambling dynamics. Here we establish fundamental limitations on the information recovery from the scrambling dynamics with arbitrary Lie group symmetries. Since our findings show universal relations between information recovery, symmetry, and coherence, they are applicable to many situations. The relations predict that the behaviour of the Hayden-Preskill black hole model changes qualitatively when the energy conservation law is assumed, and that small black holes are no longer informative mirrors. They also give a unified view for the restrictions on quantum information processing with symmetry, such as the approximate Eastin-Knill theorem and the Wigner-Araki-Yanase theorem for unitary gates.
Producing a large current typically requires large dissipation, as is the case in electric conduction, where Joule heating is proportional to the square of the current. Stochastic thermodynamics offers a framework to study nonequilibrium thermodynami
cs of small fluctuating systems, and quite recently, microscopic derivations and universal understanding of the trade-off relation between the current and dissipation have been put forward. Here we establish a universal framework clarifying how quantum coherence affects the trade-off between the current and dissipation: a proper use of coherence enhances the heat current without increasing dissipation, i.e. coherence can reduce friction. If the amount of coherence is large enough, this friction becomes virtually zero, realizing a superconducting-like ``dissipation-less heat current. Since our framework clarifies a general relation among coherence, energy flow, and dissipation, it can be applied to many branches of science. As an application to energy science, we construct a quantum heat engine cycle that exceeds the power-efficiency bound on classical engines, and effectively attains the Carnot efficiency with finite power in fast cycles. We discuss important implications of our findings with regard to the field of quantum information theory, condensed matter physics and biology.
Owing to their high photon detection efficiency, compactness, and low operating voltage, silicon photomultipliers (SiPMs) have found widespread application in many fields, including medical imaging, particle physics, and high-energy astrophysics. How
ever, the so-called optical crosstalk (OCT) phenomenon of SiPMs is a major drawback to their adoption. Secondary infrared photons are emitted inside the silicon substrate spontaneously after the avalanche process caused by the primary incident photons, and they can be detected by the surrounding photodiodes. As a result large output pulses that are equivalent to multiple photoelectrons are observed with a certain probability (OCT rate), even for single-photon events, making the charge resolution worse and increasing the rate of accidental triggers by single-photon events in applications such as atmospheric Cherenkov telescopes. In our previous study, we found that the OCT rates of single-channel SiPMs was dependent on the thickness of their protection resin window, which may be explained by photon propagation inside the resin. In the present study, we measured the OCT rate of a multichannel SiPM and those of neighboring channels caused by photon propagation. Both OCT rates were found to be dependent on the protection-window thickness. We report our OCT measurements of a multichannel SiPM and comparisons with a ray-tracing simulation.
Uncertainty relations are one of the fundamental principles in physics. It began as a fundamental limitation in quantum mechanics, and today the word {it uncertainty relation} is a generic term for various trade-off relations in nature. In this lette
r, we improve the Kennard-Robertson uncertainty relation, and clarify how much coherence we need to implement quantum measurement under conservation laws. Our approach systematically improves and reproduces the previous various refinements of the Kennard-Robertson inequality. As a direct consequence of our inequalities, we improve a well-known limitation of quantum measurements, the Wigner-Araki-Yanase-Ozawa theorem. This improvement gives an asymptotic equality for the necessary and sufficient amount of coherence to implement a quantum measurement with the desired accuracy under conservation laws.
We derive a trade-off relation between the accuracy of implementing a desired unitary evolution using a restricted set of free unitaries and the size of the assisting system, in terms of the resource generating/losing capacity of the target unitary.
In particular, this relation implies that, for any theory equipped with a resource measure satisfying lenient conditions, any resource changing unitary cannot be perfectly implemented by a free unitary applied to a system and an environment if the environment has finite dimensions. Our results are applicable to a wide class of resources including energy, asymmetry, coherence, entanglement, and magic, imposing ultimate limitations inherent in such important physical settings, as well as providing insights into operational restrictions in general resource theories.
Nature imposes many restrictions on the operations that we perform. Many of these restrictions can be interpreted in terms of {it resource} required to realize the operations. Classifying required resource for different types of operations and determ
ining the amount of resource are the crucial subjects in physics. Among many types of operations, a unitary operation is one of the most fundamental operation that has been studied for long time in terms of the resource implicitly and explicitly. Yet, it is a long standing open problem to identify the resource and to clarify the necessary and sufficient amount of resource for implementing a general unitary operation under conservation laws. In this paper, we provide a solution to this open problem. We derive an asymptotically exact equality that clarifies the necessary and sufficient amount of quantum coherence as a resource to implement arbitrary unitary operation within a desired error. In this equality, the required coherence cost is asymptotically expressed with the implementation error and the degree of violation of conservation law in the desired unitary operation. We also discuss the underlying physics in several physical situations from the viewpoint of coherence cost based on the equality. This work does not only provide a solution to a long-standing problem on the unitary control, but also clarifies the key question of the resource theory of the quantum channels in the region of resource theory of asymmetry, for the case of unitary channels.
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 probabi
lity 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.
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-reso
lution 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 {mu}m and a dimension of 9.6 mm x 9.6 mm, containing 128 strips with a pitch of 75 {mu}m, 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.
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 combini
ng 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.
