Rewindable Quantum Computation and Its Equivalence to Cloning and Adaptive Postselection

We define rewinding operators that invert quantum measurements. Then, we define complexity classes ${\sf RwBQP}$, ${\sf CBQP}$, and ${\sf AdPostBQP}$ as sets of decision problems solvable by polynomial-size quantum circuits with a polynomial number of rewinding operators, cloning operators, and adaptive postselections, respectively. Our main result is that ${\sf BPP}^{\sf PP}\subseteq{\sf RwBQP}={\sf CBQP}={\sf AdPostBQP}\subseteq{\sf PSPACE}$. As a byproduct of this result, we show that any problem in ${\sf PostBQP}$ can be solved with only postselections of outputs whose probabilities are polynomially close to one. Under the strongly believed assumption that ${\sf BQP}\nsupseteq{\sf SZK}$, or the shortest independent vectors problem cannot be efficiently solved with quantum computers, we also show that a single rewinding operator is sufficient to achieve tasks that are intractable for quantum computation. In addition, we consider rewindable Clifford and instantaneous quantum polynomial time circuits.Comment: 29 pages, 3 figures, v2: Added Result 3 and improved Result

Observational constraints on the maximum energies of accelerated particles in supernova remnants

Supernova remnants (SNRs) are thought to be the most plausible sources of Galactic cosmic rays. One of the principal questions is whether they are accelerating particles up to the maximum energy of Galactic cosmic rays ($\sim$PeV). In this paper, we summarize our recent studies on gamma-ray-emitting SNRs. We first evaluated the reliability of SNR age estimates to quantitatively discuss time dependence of their acceleration parameters. Then we systematically modeled their gamma-ray spectra to constrain the acceleration parameters. The current maximum energy estimates were found to be well below PeV for most sources. The basic time dependence of the maximum energy assuming the Sedov evolution ($\approx t^{-0.8\pm0.2}$) cannot be explained with the simplest acceleration condition (Bohm limit) and requires shock-ISM (interstellar medium) interaction. The inferred maximum energies during lifetime averaged over the sample can be expressed as $\lesssim 20$ TeV ($t_{{\rm M}}/\text{1 kyr})^{-0.8}$ with $t_{\rm M}$ being the age at the maximum, which reaches $\sim$PeV only if $t_{\rm M} \lesssim 10$ yr. The maximum energies during lifetime are suggested to have a variety of 1-2 orders of magnitude from object to object on the other hand. This variety will reflect the dependence on environments.Comment: 6 pages, 4 figures, proceedings of 7th Heidelberg International Symposium on High-Energy Gamma-Ray Astronomy (Gamma 2022

Computational self-testing for entangled magic states

In the seminal paper [Metger and Vidick, Quantum ’21], they proposed a computational self-testing protocol for Bell states in a single quantum device. Their protocol relies on the fact that the target states are stabilizer states, and hence it is highly non-trivial to reveal whether the other class of quantum states, non-stabilizer states, can be self-tested within their framework. Among non-stabilizer states, magic states are indispensable resources for universal quantum computation. In this letter, we show that a magic state for the CCZ gate can be self-tested while that for the T gate cannot. Our result is applicable to a proof of quantumness, where we can classically verify whether a quantum device generates a quantum state having non zero magic

Electric-field control of interfacial in-plane magnetic anisotropy in CoFeB/MgO junctions

Magnetoelectric coupling in metal/oxide heterostructures has opened up the possibility of controlling magnetization by voltage, i.e., electric field. However, the electric-field excitation of magnetization dynamics in perfectly in-plane and out-of-plane magnetized films have not been demonstrated so far due to zero electric-field torque originating from voltage control of perpendicular magnetic anisotropy. This limits the application of voltage-controlled magnetic anisotropy in magnetic field free control of magnetization dynamics. Here we show that magnetic annealing can induce an interfacial in-plane magnetic anisotropy of CoFeB/MgO junctions, thereby controlling the symmetry of interfacial magnetic anisotropy. The magnetic anisotropy is modulated by applying voltage: a negative bias voltage increases perpendicular magnetic anisotropy, while a positive bias voltage decreases perpendicular magnetic anisotropy and increases the in-plane magnetic anisotropy. Such a control of symmetry of the interfacial magnetic anisotropy by magnetic annealing and its tunability by electric fields is useful for developing purely voltage-controlled spintronic devices

Electric field induced parametric excitation of exchange magnons in a CoFeB/MgO junction

Inspired by the success of field-effect transistors in electronics, electric field controlled magnetization dynamics has emerged as an important integrant in low-power spintronic devices. Here, we demonstrate electric field induced parametric excitation for CoFeB/MgO junctions by using interfacial in-plane magnetic anisotropy (IMA). When the IMA and the external magnetic field are parallel to each other, magnons are efficiently excited by electric field induced parametric resonance. The corresponding wavelengths are estimated to be tuned down to exchange interaction length scales by changing the input power and frequency of the applied voltage. A generalized phenomenological model is developed to explain the underlying role of the electric field torque. Electric field control of IMA is shown to be the origin for excitation of both uniform and parametric resonance modes in the in-plane magnetized sample, a crucial element for purely electric field induced magnetization dynamics. Electric field excitation of exchange magnons, with no Joule heating, offers a good opportunity for developing nanoscale magnonic devices and exploring various nonlinear dynamics in nanomagnetic systems

Non-touch, Quick Removal of an Occluding Intratracheal Balloon Using High Intensity Focused Ultrasound and Limonene Emulsion

In recent years, fetal endoscopic tracheal occlusion （FETO） using a balloon has been clinically employed for promoting prenatal lung growth to ameliorate postnatal respiratory failure caused by severe in utero lung hypoplasia. After a successful FETO, in some limited fetal centers, planned or emergency balloon removal using another fetoscopy is performed to release the tracheal occlusion immediately before delivery. To overcome this additional fetoscopy, we previously reported an innovative simple procedure to remove the occluding balloon by bursting it with a pre-planned sequence of high intensity focused ultrasound （HIFU） irradiation. In that previous study, which used rabbits euthanized and submerged in degassed water, we inflated the balloon by injecting a mixture of perfluorocarbon and ultrasound contrast medium through a fetoscopically-guided catheter. The rate of successful balloon burst and deflation using HIFU irradiation was high enough （100％）, but the mode and timing of tracheal reopening （i.e., sudden burst or slow shrinkage of the balloon） was rather varied and collateral damage to the dermal/tracheal tissue was identified in 72.7％ of the experimental animals. Accordingly, to standardize the HIFU irradiation sequence and to achieve a reliable and secure balloon burst, we conducted another series of animal experiments in which the mixture of perfluorocarbon was replaced with “limonene emulsion” （D-limonene micelle emulsified in physiological saline） as the balloon injection fluid. In all 6 animals, we succeeded in reopening the airway by achieving an instantaneous and timely balloon burst without definite skin/tracheal damage. We conclude that HIFU irradiation together with injecting the balloon with “limonene emulsion” is an improved method for safe tracheal release from a balloon occlusion

木材内部の染色に関する「吸引染色法」の確立

　本研究の目的は、木材内部の染色に関する「吸引染色法」の確立である。「吸引染色法」とは、減圧負荷によって木材内部に染料を吸引し、着色を施す独自の染色法である。木材内部の染色に関する研究事例には、減圧加圧注入法や立木染色法があるが、染色に長時間を要することや大型設備が必要であること、色むら発生などの要因から、広範囲な実用化には至っていない。本研究では、「吸引染色法」によって、木材内部を短時間でむらなく一様に染色し、そのサイズが家具や建築部材に利用できる範囲に達することを目標とする。表面部分のみを着色した木材に比べ、内部まで染色した木材は、木材本来の質感を失わず、品があり、唐木のような美しい色合いの希少木材と同等の価値があると考える。銘木や化粧用優良大径木が世界的に枯渇している今日、建築やインテリア、プロダクト分野において、生活空間に彩りを添える素材として、染色木材の利用価値は高いと思われる。　The purpose of this study is to establish an “absorption dyeing method” to dye the inside of wood. The “absorption dyeing method” is unique in that it dyes wood by absorbing dye into it under reduced pressure. While there are examples of studies about dyeing the inside of wood, e.g. methods of decompression/pressurization injection and standing tree dyeing, such methods have not been widely adopted because they require lots of time and large facilities and produce color irregularities. This study aims to enable the inside of wood to be dyed evenly in a short period of time using an “absorption dyeing method”suitable for the sizes of furniture and building components. We believe that wood dyed on the inside retains its original texture and has the same value as beautifully colored rare wood like imported hardwood. We also believe that the current worldwide shortage of precious wood and decorative large diameter wood will make dyed wood a valuable material to be used