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Two-mode squeezing is a fascinating example of quantum entanglement manifested in cross-correlations of incompatible observables between two subsystems. At the same time, these subsystems themselves may contain no quantum signatures in their self-correlations. These properties make two-mode squeezed (TMS) states an ideal resource for applications in quantum communication. Here, we generate propagating microwave TMS states by a beam splitter distributing single mode squeezing emitted from distinct Josephson parametric amplifiers along two output paths. We experimentally study the fundamental dephasing process of quantum cross-correlations in continuous-variable propagating TMS microwave states and accurately describe it with a theory model. In this way, we gain the insight into finite-time entanglement limits and predict high fidelities for benchmark quantum communication protocols such as remote state preparation and quantum teleportation.

We describe the first ever implementation of an emulsion multi-stage shifter in an accelerator neutrino experiment. The system was installed in the neutrino monitor building in J-PARC as a part of a test experiment T60 and stable operation was maintained for a total of 126.6 days. By applying time information to emulsion films, various results were obtained. Time resolutions of 5.3 to 14.7 s were evaluated in an operation spanning 46.9 days (time resolved numbers of 3.8--1.4$\times10^{5}$). By using timing and spatial information, a reconstruction of coincident events that consisted of high multiplicity events and vertex events, including neutrino events was performed. Emulsion events were matched to events observed by INGRID, one of near detectors of the T2K experiment, with high reliability (98.5\%) and hybrid analysis was established via use of the multi-stage shifter. The results demonstrate that the multi-stage shifter is feasible for use in neutrino experiments.

Precise neutrino--nucleus interaction measurements in the sub-multi GeV region are important to reduce the systematic uncertainty in future neutrino oscillation experiments. Furthermore, the excess of ${\nu_e}$ interactions, as a possible interpretation of the existence of a sterile neutrino has been observed in such an energy region. The nuclear emulsion technique can measure all the final state particles with low energy threshold for a variety of targets (Fe, C, H${_2}$O, and so on). Its sub-$\mu$m position resolution allows measurements of the ${\nu_e}$ cross-section with good electron/gamma separation capability. We started a new experiment at J-PARC to study sub-multi GeV neutrino interactions by introducing the nuclear emulsion technique. The J-PARC T60 experiment has been implemented as a first step of such a project. Systematic neutrino event analysis with full scanning data in the nuclear emulsion detector was performed for the first time. The first neutrino event detection and its analysis is described in this paper., Comment: 26 pages, 29 figures, 4 table, prepared for submission to PTEP

Deep-inelastic scattering, in the laboratory and on the lattice, is most instructive for understanding how the nucleon is built from quarks and gluons. The long-term goal is to compute the associated structure functions from first principles. So far this has been limited to model calculations. In this Letter we propose a new method to compute the structure functions directly from the virtual, all-encompassing Compton amplitude, utilizing the operator product expansion. This overcomes issues of renormalization and operator mixing, which so far have hindered lattice calculations of power corrections and higher moments., Comment: 10 pages, 6 figures, meets published version (Phys. Rev. Letters)

A superconducting qubit in the strong dispersive regime of a circuit quantum electrodynamics system is a powerful probe for microwave photons in a cavity mode. In this regime, a qubit spectrum is split into multiple peaks, with each peak corresponding to an individual photon number in the cavity (discrete ac Stark shift). Here, we measure the qubit spectrum in the cavity that is driven continuously with a squeezed vacuum field generated by a Josephson parametric amplifier. By fitting the qubit spectrum with a model which takes into account the finite qubit excitation power, the photon number distribution, which is dissimilar from the apparent peak area ratio in the spectrum, is determined. The photon number distribution shows the even-odd photon number oscillation and quantitatively fulfills Klyshko's criterion for the nonclassicality., Comment: 10 pages, 11 figures, 1 table

Accessing hadronic form factors at large momentum transfers has traditionally presented a challenge for lattice QCD simulations. Here we demonstrate how a novel implementation of the Feynman-Hellmann method can be employed to calculate hadronic form factors in lattice QCD at momenta much higher than previously accessible. Our simulations are performed on a single set of gauge configurations with three flavours of degenerate mass quarks corresponding to $m_\pi \approx 470 \text{ MeV}$. We are able to determine the electromagnetic form factors of the pion and nucleon up to approximately $6 \text{ GeV}^2$, with results for $G_E/G_M$ in the proton agreeing well with experimental results.

We investigate implications of the use of the point-split axial vector current derived from a Wilson like fermionic action. We compute the corresponding renormalization factor nonperturbatively for one beta value. The axial charge gA calculated from this nonlocal current is found to be nearer to the physical value than computed with the local axial vector current -- computed both on the same lattice with the same action., Comment: 6 pages, 5 figures

The SU(3) flavour symmetry breaking expansion in up, down and strange quark masses is extended from hadron masses to meson decay constants. This allows a determination of the ratio of kaon to pion decay constants in QCD. Furthermore when using partially quenched valence quarks the expansion is such that SU(2) isospin breaking effects can also be determined. It is found that the lowest order SU(3) flavour symmetry breaking expansion (or Gell-Mann-Okubo expansion) works very well. Simulations are performed for 2+1 flavours of clover fermions at four lattice spacings., Comment: 16 pages, 15 figures

We propose a two-qubit quantum logic gate between a superconducting atom and a propagating microwave photon. The atomic qubit is encoded on its lowest two levels and the photonic qubit is encoded on its carrier frequencies. The gate operation completes deterministically upon reflection of a photon, and various two-qubit gates (SWAP, $\sqrt{\rm SWAP}$, and Identity) are realized through {\it in situ} control of the drive field. The proposed gate is applicable to construction of a network of superconducting atoms, which enables gate operations between non-neighboring atoms., Comment: 8 pages, 4 figures

The formulation for zero mode of a Bose-Einstein condensate beyond the Bogoliubov approximation at zero temperature [Y.Nakamura et al., Phys. Rev. A 89, 013613 (2014)] is extended to finite temperature. Both thermal and quantum fluctuations are considered in a manner consistent with a concept of spontaneous symmetry breakdown for a finite-size system. Therefore, we need a proper treatment of the zero mode operators, which invoke non-trivial enhancements in depletion condensate and thermodynamical quantities such as the specific heat. The enhancements are visible in the weak interaction case. Our approach reproduces the results of a homogeneous system in the Bogoliubov approximation in a large particle number limit., Comment: 18 pages, 6 figures

The dynamical instability of weakly interacting two-component Bose--Einstein condensates with coaxial quantized vortices is analytically investigated in a two-dimensional isotopic harmonic potential. We examine whether complex eigenvalues appear on the Bogoliubov--de Gennes equation, implying dynamical instability. Rather than solving the Bogoliubov--de Gennes equation numerically, we rely on a perturbative expansion with respect to the coupling constant which enables a simple, analytic approach. For each pair of winding numbers and for each magnetic quantum number, the ranges of inter-component coupling constant where the system is dynamically unstable are exhaustively obtained. Co-rotating and counter-rotating systems show distinctive behaviors. The latter is much more complicated than the former with respect to dynamical instability, particularly because radial excitations contribute to complex eigenvalues in counter-rotating systems., Comment: 10 pages, 6 figures

Displacement of propagating quantum states of light is a fundamental operation for quantum communication. It enables fundamental studies on macroscopic quantum coherence and plays an important role in quantum teleportation protocols with continuous variables. In our experiments we have successfully implemented this operation for propagating squeezed microwave states. We demonstrate that, even for strong displacement amplitudes, there is no degradation of the squeezing level in the reconstructed quantum states. Furthermore, we confirm that path entanglement generated by using displaced squeezed states stays constant over a wide range of the displacement power.

We discuss scale setting in the context of 2+1 dynamical fermion simulations where we approach the physical point in the quark mass plane keeping the average quark mass constant. We have simulations at four beta values, and after determining the paths and lattice spacings, we give an estimation of the phenomenological values of various Wilson flow scales., Comment: 7 pages; talk presented at Lattice 2015, the 33rd International Symposium on Lattice Field Theory 4 -18 July 2015 at Kobe International Conference Center, Kobe, Japan; PoS(LATTICE2015)264

We generate $2+1$ flavor QCD configurations near the physical point on a $96^4$ lattice employing the 6-APE stout smeared Wilson clover action with a nonperturbative $c_{\rm SW}$ and the Iwasaki gauge action at $\beta=1.82$. The physical point is estimated based on the chiral perturbation theory using several data points generated by the reweighting technique from the simulation point, wherer $m_\pi$,$m_K$ and $m_\Omega$ are used as physical inputs. The physics results include the quark masses, the hadron spectrum, the pseudoscalar meson decay constants and nucleon sigma terms, using the nonperturbative renormalization factors evaluated with the Schrodinger functional method., Comment: 7 pages, 10 figures. Proceedings of the 33rd International Symposium on Lattice Field Theory, July 14-18, 2015, Kobe, Japan

We present the quark mass and axial current renormalization factors for the RG-improved Iwasaki gauge action and three flavors of the stout smeared $O(a)$-improved Wilson quark action. We employ $\alpha=0.1$ and $n_{\mathrm{step}}=6$ for the stout link smearing parameters and all links in the quark action are replaced with the smeared links. Using the Schr\"{o}dinger functional scheme we evaluate the renormalization factors at $\beta=1.82$ where large scale simulations are being carried out., Comment: 7 pages, 2 figures, PoS.cls, PoS(LATTICE 2015)271

The Feynman-Hellmann (FH) relation offers an alternative way of accessing hadronic matrix elements through artificial modifications to the QCD Lagrangian. In particular, a FH-motivated method provides a new approach to calculations of disconnected contributions to matrix elements and high-momentum nucleon and pion form factors. Here we present results for the total nucleon axial charge, including a statistically significant non-negative total disconnected quark contribution of around $-5\%$ at an unphysically heavy pion mass. Extending the FH relation to finite-momentum transfers, we also present calculations of the pion and nucleon electromagnetic form factors up to momentum transfers of around 7-8 GeV$^2$. Results for the nucleon are not able to confirm the existence of a sign change for the ratio $\frac{G_E}{G_M}$, but suggest that future calculations at lighter pion masses will provide fascinating insight into this behaviour at large momentum transfers.

For Wilson and clover fermions traditional formulations of the axial vector current do not respect the continuum Ward identity which relates the divergence of that current to the pseudoscalar density. Here we propose to use a point-split or one-link axial vector current whose divergence exactly satisfies a lattice Ward identity, involving the pseudoscalar density and a number of irrelevant operators. We check in one-loop lattice perturbation theory with SLiNC fermion and gauge plaquette action that this is indeed the case including order $O(a)$ effects. Including these operators the axial Ward identity remains renormalisation invariant. First preliminary results of a nonperturbative check of the Ward identity are also presented., Comment: 7 pages, 3 figures, Proceedings of the 33rd International Symposium on Lattice Field Theory, 14-18 July 2015, Kobe, Japan

We experimentally implement a system of cavity optomagnonics, where a sphere of ferromagnetic material supports whispering gallery modes (WGMs) for photons and the magnetostatic mode for magnons. We observe pronounced nonreciprocity and asymmetry in the sideband signals generated by the magnon-induced Brillouin scattering of light. The spin-orbit coupled nature of the WGM photons, their geometric birefringence and the time-reversal symmetry breaking in the magnon dynamics impose the angular-momentum selection rules in the scattering process and account for the observed phenomena. The unique features of the system may find interesting applications at the crossroad between quantum optics and spintronics., Comment: 5 pages (4 figures) + supplemental material, accepted by PRL

We present results on the pseudoscalar meson masses from a fully dynamical simulation of QCD+QED. We concentrate particularly on violations of isospin symmetry. We calculate the $\pi^+$-$\pi^0$ splitting and also look at other isospin violating mass differences. We have presented results for these isospin splittings in arXiv:1508.06401 [hep-lat]. In this paper we give more details of the techniques employed, discussing in particular the question of how much of the symmetry violation is due to QCD, arising from the different masses of the $u$ and $d$ quarks, and how much is due to QED, arising from the different charges of the quarks. This decomposition is not unique, it depends on the renormalisation scheme and scale. We suggest a renormalisation scheme in which Dashen's theorem for neutral mesons holds, so that the electromagnetic self-energies of the neutral mesons are zero, and discuss how the self-energies change when we transform to a scheme such as $\bar{MS}$, in which Dashen's theorem for neutral mesons is violated., Comment: 22 pages, 7 figures. Replaced by version accepted for publication. One figure added, some discussions expanded. Conclusions unchanged

We present a calculation of the SU(3)-breaking corrections to the hyperon transition vector form factors to $\mathcal{O}(p^4)$ in heavy baryon chiral perturbation theory with finite-range regularisation. Both octet and decuplet degrees of freedom are included. We formulate a chiral expansion at the kinematic point $Q^2=-(M_{B_1}-M_{B_2})^2$, which can be conveniently accessed in lattice QCD. The two unknown low-energy constants at this point are constrained by lattice QCD simulation results for the $\Sigma^-\rightarrow n$ and $\Xi^0\rightarrow \Sigma^+$ transition form factors. Hence we determine lattice-informed values of $f_1$ at the physical point. This work constitutes progress towards the precise determination of $|V_{us}|$ from hyperon semileptonic decays.

The spin decomposition of the proton is a long-standing topic of much interest in hadronic physics. Lattice QCD has had much success in calculating the connected contributions to the quark spin. However, complete calculations, which necessarily involve gluonic and strange-quark contributions, still present some challenges. These "disconnected" contributions typically involve small signals hidden against large statistical backgrounds and rely on computationally intensive stochastic techniques. In this work we demonstrate how a Feynman-Hellmann approach may be used to calculate such quantities, by measuring shifts in the proton energy arising from artificial modifications to the QCD action. We find a statistically significant non-zero result for the disconnected quark spin contribution to the proton of about -5% at a pion mass of 470 MeV.

Gate operations in a quantum information processor are generally realized by tailoring specific periods of free and driven evolution of a quantum system. Unwanted environmental noise, which may in principle be distinct during these two periods, acts to decohere the system and increase the gate error rate. While there has been significant progress characterizing noise processes during free evolution, the corresponding driven-evolution case is more challenging as the noise being probed is also extant during the characterization protocol. Here we demonstrate the noise spectroscopy (0.1 - 200 MHz) of a superconducting flux qubit during driven evolution by using a robust spin-locking pulse sequence to measure relaxation (T1rho) in the rotating frame. In the case of flux noise, we resolve spectral features due to coherent fluctuators, and further identify a signature of the 1MHz defect in a time-domain spin-echo experiment. The driven-evolution noise spectroscopy complements free-evolution methods, enabling the means to characterize and distinguish various noise processes relevant for universal quantum control.

Lattice QCD simulations are now reaching a precision where isospin breaking effects become important. Previously, we have developed a program to systematically investigate the pattern of flavor symmetry beaking within QCD and successfully applied it to meson and baryon masses involving up, down and strange quarks. In this Letter we extend the calculations to QCD + QED and present our first results on isospin splittings in the pseudoscalar meson and baryon octets. In particular, we obtain the nucleon mass difference of $M_n-M_p=1.35(18)(8)\,\mbox{MeV}$ and the electromagnetic contribution to the pion splitting $M_{\pi^+}-M_{\pi^0}=4.60(20)\,\mbox{MeV}$. Further we report first determination of the separation between strong and electromagnetic contributions in the $\bar{MS}$ scheme., Comment: 14 pages, 10 figures, text and figures added, Journal version

We give a determination of the phenomenological value of the Wilson (or gradient) flow scales t0 and w0 for 2+1 flavours of dynamical quarks. The simulations are performed keeping the average quark mass constant, which allows the approach to the physical point to be made in a controlled manner. O(a) improved clover fermions are used and together with four lattice spacings this allows the continuum extrapolation to be taken., Comment: 24 pages, 11 figures

In this Reply, we respond to the above Comment. Our computation [Phys. Rev. D 91 (2015) 074512] only took into account pure QCD effects, arising from quark mass differences, so it is not surprising that there are discrepancies in isospin splittings and in the Sigma - Lambda mixing angle. We expect that these discrepancies will be smaller in a full calculation incorporating QED effects., Comment: 5 pages

We study the dynamics of a nonlinear oscillator near the critical point where period-two vibrations are first excited with the increasing amplitude of parametric driving. Above the threshold, quantum fluctuations induce transitions between the period-two states over the quasienergy barrier. We find the effective quantum activation energies for such transitions and their scaling with the difference of the driving amplitude from its critical value. We also find the scaling of the fluctuation correlation time with the quantum noise parameters in the critical region near the threshold.