Experimental Bayesian Quantum Phase Estimation on a Silicon Photonic Chip

Quantum phase estimation is a fundamental subroutine in many quantum algorithms, including Shor's factorization algorithm and quantum simulation. However, so far results have cast doubt on its practicability for near-term, non-fault tolerant, quantum devices. Here we report experimental results demonstrating that this intuition need not be true. We implement a recently proposed adaptive Bayesian approach to quantum phase estimation and use it to simulate molecular energies on a Silicon quantum photonic device. The approach is verified to be well suited for pre-threshold quantum processors by investigating its superior robustness to noise and decoherence compared to the iterative phase estimation algorithm. This shows a promising route to unlock the power of quantum phase estimation much sooner than previously believed

PSR J1024-0719:A Millisecond Pulsar in an Unusual Long-Period Orbit

PSR J1024-0719 is a millisecond pulsar that was long thought to be isolated. However, puzzling results concerning its velocity, distance, and low rotational period derivative have led to a reexamination of its properties. We present updated radio timing observations along with new and archival optical data which show that PSR J1024-0719 is most likely in a long-period (2-20 kyr) binary system with a low-mass (approximate to 0.4 M-circle dot), low-metallicity (Z approximate to -0.9 dex) main-sequence star. Such a system can explain most of the anomalous properties of this pulsar. We suggest that this system formed through a dynamical exchange in a globular cluster that ejected it into a halo orbit, which is consistent with the low observed metallicity for the stellar companion. Further astrometric and radio timing observations such as measurement of the third period derivative could strongly constrain the range of orbital parameters

Search for charged Higgs bosons in e+e−e^+ e^- collisions at centre-of-mass energies between 130 and 183 GeV

A search for pair-produced charged Higgs bosons is performed with the L3 detector at LEP using data collected at centre-of-mass energies from \mbox{130 to 183 \GeV{}}, corresponding to an integrated luminosity of 88.3 \pb. The Higgs decays into a charm and a strange quark or into a tau lepton and its associated neutrino are considered. The observed candidates are consistent with the expectations from Standard Model background processes. A lower limit of 57.5 \GeV{} on the charged Higgs mass is derived at 95\% CL, independent of the decay branching ratio \mathrm{Br(H^\pm\ra \tau\nu)}

Search for R-Parity Breaking Sneutrino Exchange at LEP

We report on a search for R--parity breaking effects due to supersymmetric tau--sneutrino exchange in the reactions e+e- to e+e- and e+e- to mu+mu- at centre--of--mass energies from 91~{\GeV} to 172~{\GeV}, using the L3 detector at LEP. No evidence for deviations from the Standard Model expectations of the measured cross sections and forward--backward asymmetries for these reactions is found. Upper limits for the couplings $\lambda_{131}$ and $\lambda_{232}$ for sneutrino masses up to m_{\SNT} \leq 190~\GeV are determined from an analysis of the expected effects due to tau sneutrino exchange

Determination of the number of light neutrino species from single photon production at LEP

A determination of the number of light neutrino families performed by measuring the cross section of single photon production in \ee\ collision near the \Zo\ resonance is reported. From an integrated luminosity of $100~\mathrm{pb^{-1}}$, collected during the years 1991--94, we have observed 2091 single photon candidates with an energy above 1~\GeV\ in the polar angular region $45^\circ < \theta_\gamma < 135^\circ$. From a maximum likelihood fit to the single photon cross section, the \Zo\ decay width into invisible particles is measured to be \Ginv = 498 \pm 12 \mathrm{(stat)} \pm 12 \mathrm{(sys)~MeV}. Using the Standard Model couplings of neutrinos to the \Zo, the number of light neutrino species is determined to be $N_\nu = 2.98 \pm 0.07 (\mathrm{stat}) \pm 0.07 (\mathrm{sys}).

QCD results from studies of hadronic events produced in e+e−e^+ e^- annihilations at s\sqrt{s} = 183 GeV

We present results obtained from a study of the structure of hadronic events recorded by the L3 detector at a centre-of-mass energy of 183 GeV. The data sample corresponds to an integrated luminosity of 55.3 $\mathrm{pb^{-1}}$. % collected during the high energy run of 1997. The distributions of event shape variables and the energy dependence of their mean values are measured. From a comparison with resummed $\cal{O

Search for new physics phenomena in fermion-pair production at LEP

The measurements of hadron and lepton--pair production cross sections and lepton--pair forward--backward asymmetries performed with the L3 detector at centre--of--mass energies between 130 GeV and 172 GeV are used to search for new physics phenomena. New physics effects involving four fermion vertices -- contact interactions -- are looked for in all channels. For hadron production the exchange of virtual leptoquarks and scalar quarks is studied. No evidence for deviations from the Standard Model expectations is found. Lower limits on the scale $\Lambda$ of contact interactions in the range 1.2 -- 7.1 TeV are obtained at the 95\% confidence level for various models. Upper limits on the coupling strengths of leptoquarks and scalar quarks are derived

Measurement of the effective weak mixing angle by jet-charge asymmetry in hadronic decays of the Z boson

The coupling of the Z boson to quarks is studied in a sample of about 3.5 million hadronic Z decays collected by the L3 experiment at LEP from 1991 to 1995. The forward-backward quark charge asymmet ry is measured by means of a jet charge technique. From the measured asymmetries, the effective weak mixing angle is determined to be \begin{center} $\STE = 0.2327 \pm 0.0012(\mbox{\emph{stat.}} ) \pm 0.0013(\mbox{\emph{syst.}}).

Measurement of the inclusive charmless semileptonic branching fraction of beauty hadrons and a determination of |VubV_{ub}| at LEP

A measurement of the inclusive charmless semileptonic branching fraction of beauty hadrons, $\mathrm{b}\rightarrow\mathrm{X}_\mathrm{u }\ell\nu$, has been performed using almost two million hadronic Z decays collected by the L3 experiment at LEP, yielding the result: \begin{displaymath} \mathrm{Br}(\mathrm{b}\rightarrow\mathrm{X}_\mathr m{u}\ell\nu) = (3.3 \pm 1.0 \pm 1.7)\times 10^{-3}. \end{displaymath} The first uncertainty is statistical and the second is systematic. The modulus of the Cabibbo-Kobayashi-Maskawa matrix element $\mathrm{V_{ub}}$ extracted from this measurement is: \begin{displaymath} |\mathrm{V_{ub}}| = (6.0\, ^{+0.8}_{-1.0} \, ^{+1.4}_{-1.9} \pm 0.2)\times 10^{-3}, \end{displaymath} where the uncertainties are statistical, systematic and theoretical, respectively

Local multiplicity fluctuations in hadronic Z decay

Local multiplicity fluctuations in hadronic Z decays are studied using the L3 detector at LEP. Bunching parameters are used for the first time in addition to the normalised factorial moment method. The bunching parameters directly demonstrate that the fluctuations in rapidity are multifractal. Monte Carlo models show overall agreement with the data, reproducing the trend, although not always the magnitude, of the factorial moments and bunching parameters