Impossibility of Classically Simulating One-Clean-Qubit Model with Multiplicative Error

The one-clean-qubit model (or the deterministic quantum computation with one quantum bit model) is a restricted model of quantum computing where all but a single input qubits are maximally mixed. It is known that the probability distribution of measurement results on three output qubits of the one-clean-qubit model cannot be classically efficiently sampled within a constant multiplicative error unless the polynomial-time hierarchy collapses to the third level [T. Morimae, K. Fujii, and J. F. Fitzsimons, Phys. Rev. Lett. 112, 130502 (2014)PRLTAO0031-900710.1103/PhysRevLett.112.130502]. It was open whether we can keep the no-go result while reducing the number of output qubits from three to one. Here, we solve the open problem affirmatively. We also show that the third-level collapse of the polynomial-time hierarchy can be strengthened to the second-level one. The strengthening of the collapse level from the third to the second also holds for other subuniversal models such as the instantaneous quantum polynomial model [M. Bremner, R. Jozsa, and D. J. Shepherd, Proc. R. Soc. A 467, 459 (2011)PRLAAZ1364-502110.1098/rspa.2010.0301] and the boson sampling model [S. Aaronson and A. Arkhipov, STOC 2011, p. 333]. We additionally study the classical simulatability of the one-clean-qubit model with further restrictions on the circuit depth or the gate types.

A coherent Ising machine for 2000-node optimization problems

The analysis and optimization of complex systems can be reduced to mathematical problems collectively known as combinatorial optimization. Many such problems can be mapped onto ground-state search problems of the Ising model, and various artificial spin systems are now emerging as promising approaches. However, physical Ising machines have suffered from limited numbers of spin-spin couplings because of implementations based on localized spins, resulting in severe scalability problems. We report a 2000-spin network with all-to-all spin-spin couplings. Using a measurement and feedback scheme, we coupled time-multiplexed degenerate optical parametric oscillators to implement maximum cut problems on arbitrary graph topologies with up to 2000 nodes. Our coherent Ising machine outperformed simulated annealing in terms of accuracy and computation time for a 2000-node complete graph.

A fully programmable 100-spin coherent Ising machine with all-to-all connections

Unconventional, special-purpose machines may aid in accelerating the solution of some of the hardest problems in computing, such as large-scale combinatorial optimizations, by exploiting different operating mechanisms than those of standard digital computers. We present a scalable optical processor with electronic feedback that can be realized at large scale with room-temperature technology. Our prototype machine is able to find exact solutions of, or sample good approximate solutions to, a variety of hard instances of Ising problems with up to 100 spins and 10,000 spin-spin connections.

Dysregulation of a potassium channel, THIK-1, targeted by caspase-8 accelerates cell shrinkage

Activation of caspases is crucial for the execution of apoptosis. Although the caspase cascade associated with activation of the initiator caspase-8 (CASP8) has been investigated in molecular and biochemical detail, the physiological role of CASP8 is not fully understood. Here, we identified a two-pore domain potassium channel, tandem-pore domain halothane-inhibited K⁺ channel 1 (THIK-1), as a novel CASP8 substrate. The intracellular region of THIK-1 was cleaved by CASP8 in apoptotic cells. Overexpression of THIK-1, but not its mutant lacking the CASP8-target sequence in the intracellular portion, accelerated cell shrinkage in response to apoptotic stimuli. In contrast, knockdown of endogenous THIK-1 by RNA interference resulted in delayed shrinkage and potassium efflux. Furthermore, a truncated THIK-1 mutant lacking the intracellular region, which mimics the form cleaved by CASP8, led to a decrease of cell volume of cultured cells without apoptotic stimulation and excessively promoted irregular development of Xenopus embryos. Taken together, these results indicate that THIK-1 is involved in the acceleration of cell shrinkage. Thus, we have demonstrated a novel physiological role of CASP8: creating a cascade that advances the cell to the next stage in the apoptotic process.

Computational quantum-classical boundary of noisy commuting quantum circuits

It is often said that the transition from quantum to classical worlds is caused by decoherence originated from an interaction between a system of interest and its surrounding environment. Here we establish a computational quantum-classical boundary from the viewpoint of classical simulatability of a quantum system under decoherence. Specifically, we consider commuting quantum circuits being subject to decoherence. Or equivalently, we can regard them as measurement-based quantum computation on decohered weighted graph states. To show intractability of classical simulation in the quantum side, we utilize the postselection argument and crucially strengthen it by taking noise effect into account. Classical simulatability in the classical side is also shown constructively by using both separable criteria in a projected-entangled-pair-state picture and the Gottesman-Knill theorem for mixed state Clifford circuits. We found that when each qubit is subject to a single-qubit complete-positive-trace-preserving noise, the computational quantum-classical boundary is sharply given by the noise rate required for the distillability of a magic state. The obtained quantum-classical boundary of noisy quantum dynamics reveals a complexity landscape of controlled quantum systems. This paves a way to an experimentally feasible verification of quantum mechanics in a high complexity limit beyond classically simulatable region.

Leiomyoblastoma causing acute gastric outlet obstruction in an infant

A 1-year-old boy had acute gastric outlet obstruction, the cause of which was a prepyloric submucosal mass. The mass and the ulcerated overlying mucosa were excised. The histological diagnosis was leiomyoblastoma with parenchymatous hemorrhage. Apparently, he is the youngest patient reported to have this disease.

[Treatment with arbekacin of surgical infections by resistant strains of Staphylococcus aureus. Arbekacin Study Group]

The frequency of infection by methicillin-resistant Staphylococcus aureus (MRSA) is high in Japan and control of such strains is urgently needed. Arbekacin (ABK), a semisynthetic aminoglycoside, has potent activity against S. aureus, including resistant strains, and against Gram-negative bacteria as well. For this reason, in surgical infections (which are often caused by more than one bacterium), this drug might be particularly effective. We calculated the MIC and the decrease in the MIC when cultures of 59 resistant strains of S. aureus isolated in our wards at Osaka City University Hospital, contained arbekacin in the medium. We also used the drug to treat 12 infections caused by resistant strains of S. aureus. The MICs of vancomycin had a single peak at 0.5 microgram/ml, and those for ABK had double peaks at 0.5 and 4.0 micrograms/ml. The effect of arbekacin in lowering the MIC of minocycline (MINO) was slight because of the low MIC of MINO. Effects on fosfomycin (FOM), ampicillin, clavulanic acid/ticarcillin, cefotiam, cefuzonam, flomoxef, and imipenem/cilastatin were strong; the peaks were lowered by 1/2(7)-1/2(11). When 1.0 micrograms/ml ABK was present in the medium, the efficacy of FOM was increased enough that, by prediction from the pharmacokinetics of FOM (blood level when given at the usual dose), all but one (2%) of the 47 resistant strains would be eradicated clinically. If 2.0 micrograms/ml ABK were in the medium, all strain would be eradicated, by our calculations. We treated 11 infections and one colonization by resistant strains of S. aureus with ABK and evaluated the response in these cases of infection. Four infections were treated with FOM as well. The clinical efficacy was good in four infections (three patients), fair in four, and poor in three, for an efficacy rate of 36%. All presumed causative bacteria were eradicated in two (18%) of the 11 infections and S. aureus strains were eradicated in three (27%) of the 11 infections. No symptoms of side effects were reported, but blood urea nitrogen and creatinine rose in a 72-year-old woman with duodenal perforation and peritonitis. The MIC levels of ABK were satisfactory, but clinical efficacy for staphylococcal infections caused by resistant strains was unsatisfactory.

Esophagitis in infants with hypertrophic pyloric stenosis: a source of hematemesis

This study was undertaken to clarify the source of blood in the vomitus of patients with hypertrophic pyloric stenosis (HPS). Twenty-one infants with HPS were examined. Hematemesis was noted in 14 infants. Esophagogastric endoscopy showed a 100% incidence of esophagitis and in one patient gastric erosion was also observed. Histological study of the esophageal mucosa showed evidence of esophagitis in 18 patients (85.7%). Preoperative pH monitoring showed gastroesophageal reflux (GER) in all infants. Excessive acid exposure (> or = 7%) was significantly correlated with the grade of esophagitis and the incidence of hematemesis, whereas acid exposure time was shorter in the cases without histological esophagitis. These results suggested that the source of bleeding in HPS is the esophageal mucosa affected by esophagitis secondary to excessive acid reflux. Although there is obvious massive gastroesophageal reflux in HPS, it is too difficult to evaluate the lower esophageal sphincter function in HPS.

[Limits of duration of chest tube drainage in the first episode of spontaneous pneumothorax]

We treated three patients with spontaneous left pneumothorax who underwent a long period of chest tube drainage before surgery. Case 1 was a 61-year-old man. On day 13 after drainage started, much air leakage occurred and surgery was done the next day. Case 2 was a 57-year-old man. Drainage failed to allow the air leakage to seal. The patient did not consent to surgery for about a month, but on day 38 after drainage started, he underwent surgery. Case 3 was a 19-year-old man. First, chest tube drainage was successful and he was extubated on day 16. However, pneumothorax recurred the next day. Liver dysfunction delayed surgical treatment, and the patient underwent surgery on day 54 after the first drainage. Postoperatively, he developed wound infection of the chest tube route and aseptic pleurisy of unknown origin. Limits of duration of unsuccessful chest tube drainage for the first episode of spontaneous pneumothorax are controversial. These cases suggest that when two weeks of chest tube drainage is unsuccessful, surgery should be undertaken in view of postoperative complication and social indications.

Manometric diagnosis of Hirschsprung's disease in the neonatal period

A newly designed semiconductor manometer was assembled for anorectal manometry in the neonatal period. Sixty apparently healthy neonates and 17 patients who presented gastrointestinal obstructive symptoms were examined by the eighth day of life. All 60 apparently healthy neonates showed a normal fluctuating wave and rectoanal reflex. Prematurity and postnatal age do not influence the normal rectoanal reflex. Among 17 patients, 5 were diagnosed as having Hirschsprung's disease based on absence of the reflex. There were no false negative or false positive results among these cases. It appears that anorectal manometry could be a reliable diagnostic test of Hirschsprung's disease even in the neonatal period.

Neonatal gastric perforations; a diagnostic clue in pre-perforative phase

This paper is a retrospective analysis of the pre-perforative clinical picture in twenty-seven neonates with gastric perforations. In fifteen there was a remarkably consistent progressive pattern in the preperforative clinical course. We separated the clinical course of the disease into three distinct stages in relation to pathological changes in the gastric wall i.e. gastric ischemia and dysfunction, transmural peritonitis and paralytic ileus, and actual perforation. Emphasis was placed on the existance of a clinically detectable pre-perforative phase which, if interpreted correctly, should lead to earlier diagnosis and consequently more satisfactory therapeutic results.

Perineal groove and perineal canal

Perineal groove is a rare congenital wet sulcus extending from the fourchette to the anus. With awareness of the lesion, surgery can be avoided. Perineal canal is a congenital anorectovestibular fistula coexistent with normal anus. Recently, it has become evident that these lesions are relatively common and clinically important variants of anorectal anomalies. We now report one patient each with these anomalies and briefly review the surgical problems.

Congenital pyloric atresia: a report of three cases

Congenital pyloric atresia, a rare malformation producing gastric outlet obstruction during the neonatal period, was found in three patients. Sixty per cent of these malformations are membranous in type. Excision of the membrane and Heineke-Mikulicz pyloroplasty, which has been advocated as the procedure of choice, inevitably results in postoperative duodenogastric bile reflux. We suggest that to minimize reflux and hence possible increased risk of future development of gastric ulcer, maximal preservation of pyloric function in the operative management of the malformations is important.

Full-thickness rectal punch biopsy for the diagnosis of Hirschsprung's disease

The authors propose a full-thickness rectal punch biopsy method for the diagnosis of Hirschsprung's disease when the results of other diagnostic investigations have been equivocal. This procedure has been utilized in 48 patients in the last 8 yr and the method was diagnostically reliable.