MINOS Results, Progress and Future Prospects

The MINOS long baseline experiment has been collecting neutrino beam data since March 2005 and has accumulated 3 x 10^{20} protons-on-target (POT) to date. MINOS uses Fermilab's NuMI neutrino beam which is measured by two steel-scintillator tracking calorimeters, one at Fermilab and the other 735 km downstream, in northern Minnesota. By observing the oscillatory structure in the neutrino energy spectrum, MINOS can precisely measure the neutrino oscillation parameters in the atmospheric sector. From analysis of the first year of data, corresponding to 1.27 x 10^{20} POT, these parameters were determined to be |\Delta m^2_{32}|=2.74^{+0.44}_{-0.26} x 10^{-3} eV^2 and sin^2(2\theta_{23})>0.87 (68% C.L.). MINOS is able to measure the neutrino velocity by comparing the arrival times of the neutrino beam in its two detectors. Using a total of 473 Far Detector events, (v-c)/c = (5.1 +/- 2.9) x 10^{-5} (68% C.L.) was measured. In addition, we report recent progress in the analysis of neutral current events and give an outline of experimental goals for the future.Comment: 8 pages, 7 figures, prepared for the proceedings of the XLIInd Rencontres de Moriond, Electroweak Interactions and Unified Theories, La Thuile, March 200

Transition probabilities and measurement statistics of postselected ensembles

It is well-known that a quantum measurement can enhance the transition probability between two quantum states. Such a measurement operates after preparation of the initial state and before postselecting for the final state. Here we analyze this kind of scenario in detail and determine which probability distributions on a finite number of outcomes can occur for an intermediate measurement with postselection, for given values of the following two quantities: (i) the transition probability without measurement, (ii) the transition probability with measurement. This is done for both the cases of projective measurements and of generalized measurements. Among other constraints, this quantifies a trade-off between high randomness in a projective measurement and high measurement-modified transition probability. An intermediate projective measurement can enhance a transition probability such that the failure probability decreases by a factor of up to 2, but not by more.Comment: 23 pages, 5 figures, minor updat

The Dynamics of 1D Quantum Spin Systems Can Be Approximated Efficiently

In this Letter we show that an arbitrarily good approximation to the propagator e^{itH} for a 1D lattice of n quantum spins with hamiltonian H may be obtained with polynomial computational resources in n and the error \epsilon, and exponential resources in |t|. Our proof makes use of the finitely correlated state/matrix product state formalism exploited by numerical renormalisation group algorithms like the density matrix renormalisation group. There are two immediate consequences of this result. The first is that the Vidal's time-dependent density matrix renormalisation group will require only polynomial resources to simulate 1D quantum spin systems for logarithmic |t|. The second consequence is that continuous-time 1D quantum circuits with logarithmic |t| can be simulated efficiently on a classical computer, despite the fact that, after discretisation, such circuits are of polynomial depth.Comment: 4 pages, 2 figures. Simplified argumen

Stochastic feedback control of quantum transport to realize a dynamical ensemble of two nonorthogonal pure states

A Markovian open quantum system which relaxes to a unique steady state $\rho_{ss}$ of finite rank can be decomposed into a finite physically realizable ensemble (PRE) of pure states. That is, as shown by Karasik and Wiseman [Phys. Rev. Lett. 106, 020406 (2011)], in principle there is a way to monitor the environment so that in the long time limit the conditional state jumps between a finite number of possible pure states. In this paper we show how to apply this idea to the dynamics of a double quantum dot arising from the feedback control of quantum transport, as previously considered by one of us and co-workers [Phys. Rev. B 84, 085302 (2011)]. Specifically, we consider the limit where the system can be described as a qubit, and show that while the control scheme can always realize a two-state PRE, in the incoherent tunneling regime there are infinitely many PREs compatible with the dynamics that cannot be so realized. For the two-state PREs that are realized, we calculate the counting statistics and see a clear distinction between the coherent and incoherent regimes.Comment: 11 pages, 4 figure

ZγZ\gamma production at NNLO including anomalous couplings

In this paper we present a next-to-next-to-leading order (NNLO) QCD calculation of the processes $pp\rightarrow l^+l^-\gamma$ and $pp\rightarrow \nu\bar\nu\gamma$ that we have implemented in MCFM. Our calculation includes QCD corrections at NNLO both for the Standard Model (SM) and additionally in the presence of $Z\gamma\gamma$ and $ZZ\gamma$ anomalous couplings. We compare our implementation, obtained using the jettiness slicing approach, with a previous SM calculation and find broad agreement. Focusing on the sensitivity of our results to the slicing parameter, we show that using our setup we are able to compute NNLO cross sections with numerical uncertainties of about $0.1\%$, which is small compared to residual scale uncertainties of a few percent. We study potential improvements using two different jettiness definitions and the inclusion of power corrections. At $\sqrt{s}=13$ TeV we present phenomenological results and consider $Z\gamma$ as a background to $H\to Z\gamma$ production. We find that, with typical cuts, the inclusion of NNLO corrections represents a small effect and loosens the extraction of limits on anomalous couplings by about $10\%$.Comment: 30 pages, 14 figure

Invariant Solution underlying Oblique Stripe Patterns in Plane Couette Flow

When subcritical shear flows transition to turbulence, laminar and turbulent flow often coexists in space, giving rise to turbulent-laminar patterns. Most prominent are regular stripe patterns with large-scale periodicity and oblique orientation. Oblique stripes are a robust phenomenon, observed in experiments and flow simulations, yet their origin remains unclear. We demonstrate the existence of an invariant equilibrium solution of the fully nonlinear 3D Navier-Stokes equations that resembles the oblique pattern of turbulent-laminar stripes in plane Couette flow. We uncover the origin of the stripe equilibrium and show how it emerges from the well-studied Nagata equilibrium via two successive symmetry-breaking bifurcations