Propagating Gottesman-Kitaev-Preskill states encoded in an optical oscillator

A quantum computer with low-error, high-speed quantum operations and capability for interconnections is required for useful quantum computations. A logical qubit called Gottesman-Kitaev-Preskill (GKP) qubit in a single Bosonic harmonic oscillator is efficient for mitigating errors in a quantum computer. The particularly intriguing prospect of GKP qubits is that entangling gates as well as syndrome measurements for quantum error correction only require efficient, noise-robust linear operations. To date, however, GKP qubits have been only demonstrated at mechanical and microwave frequency in a highly nonlinear physical system. The physical platform that naturally provides the scalable linear toolbox is optics, including near-ideal loss-free beam splitters and near-unit efficiency homodyne detectors that allow to obtain the complete analog syndrome for optimized quantum error correction. Additional optical linear amplifiers and specifically designed GKP qubit states are then all that is needed for universal quantum computing. In this work, we realize a GKP state in propagating light at the telecommunication wavelength and demonstrate homodyne meausurements on the GKP states for the first time without any loss corrections. Our GKP states do not only show non-classicality and non-Gaussianity at room temperature and atmospheric pressure, but unlike the existing schemes with stationary qubits, they are realizable in a propagating wave system. This property permits large-scale quantum computation and interconnections, with strong compatibility to optical fibers and 5G telecommunication technology.Comment: 11 pages, 5 figure

DNA Methylation Dynamics in Human Induced Pluripotent Stem Cells over Time

Epigenetic reprogramming is a critical event in the generation of induced pluripotent stem cells (iPSCs). Here, we determined the DNA methylation profiles of 22 human iPSC lines derived from five different cell types (human endometrium, placental artery endothelium, amnion, fetal lung fibroblast, and menstrual blood cell) and five human embryonic stem cell (ESC) lines, and we followed the aberrant methylation sites in iPSCs for up to 42 weeks. The iPSCs exhibited distinct epigenetic differences from ESCs, which were caused by aberrant methylation at early passages. Multiple appearances and then disappearances of random aberrant methylation were detected throughout iPSC reprogramming. Continuous passaging of the iPSCs diminished the differences between iPSCs and ESCs, implying that iPSCs lose the characteristics inherited from the parent cells and adapt to very closely resemble ESCs over time. Human iPSCs were gradually reprogrammed through the “convergence” of aberrant hyper-methylation events that continuously appeared in a de novo manner. This iPS reprogramming consisted of stochastic de novo methylation and selection/fixation of methylation in an environment suitable for ESCs. Taken together, random methylation and convergence are driving forces for long-term reprogramming of iPSCs to ESCs

Catalytic mechanism of the tyrosinase reaction toward the Tyr98 residue in the caddie protein.

Tyrosinase (EC 1.14.18.1), a copper-containing monooxygenase, catalyzes the conversion of phenol to the corresponding ortho-quinone. The Streptomyces tyrosinase is generated as a complex with a "caddie" protein that facilitates the transport of two copper ions into the active center. In our previous study, the Tyr98 residue in the caddie protein, which is accommodated in the pocket of active center of tyrosinase, has been found to be converted to a reactive quinone through the formations of the μ-η2:η2-peroxo-dicopper(II) and Cu(II)-dopasemiquinone intermediates. Until now-despite extensive studies for the tyrosinase reaction based on the crystallographic analysis, low-molecular-weight models, and computer simulations-the catalytic mechanism has been unable to be made clear at an atomic level. To make the catalytic mechanism of tyrosinase clear, in the present study, the cryo-trapped crystal structures were determined at very high resolutions (1.16-1.70 Å). The structures suggest the existence of an important step for the tyrosinase reaction that has not yet been found: that is, the hydroxylation reaction is triggered by the movement of CuA, which induces the syn-to-anti rearrangement of the copper ligands after the formation of μ-η2:η2-peroxo-dicopper(II) core. By the rearrangement, the hydroxyl group of the substrate is placed in an equatorial position, allowing the electrophilic attack to the aromatic ring by the Cu2O2 oxidant

Activation Mechanism of the <i>Streptomyces</i> Tyrosinase Assisted by the Caddie Protein

Tyrosinase (EC 1.14.18.1), which possesses two copper ions at the active center, catalyzes a rate-limiting reaction of melanogenesis, that is, the conversion of a phenol to the corresponding <i>ortho</i>-quinone. The enzyme from the genus <i>Streptomyces</i> is generated as a complex with a “caddie” protein that assists the transport of two copper ions into the active center. In this complex, the Tyr⁹⁸ residue in the caddie protein was found to be accommodated in the pocket of the active center of tyrosinase, probably in a manner similar to that of l-tyrosine as a genuine substrate of tyrosinase. Under physiological conditions, the addition of the copper ion to the complex releases tyrosinase from the complex, in accordance with the aggregation of the caddie protein. The release of the copper-bound tyrosinase was found to be accelerated by adding reducing agents under aerobic conditions. Mass spectroscopic analysis indicated that the Tyr⁹⁸ residue was converted to a reactive quinone, and resonance Raman spectroscopic analysis indicated that the conversion occurred through the formations of μ-η²:η²-peroxo-dicopper­(II) and Cu­(II)-semiquinone. Electron paramagnetic resonance analysis under anaerobic conditions and Fourier transform infrared spectroscopic analysis using CO as a structural probe under anaerobic conditions indicated that the copper transportation process to the active center is a reversible event in the tyrosinase/caddie complex. Aggregation of the caddie protein, which is triggered by the conversion of the Tyr⁹⁸ residue to dopaquinone, may ensure the generation of fully activated tyrosinase