Coherent control via weak measurements in P 31 single-atom electron and nuclear spin qubits

The understanding of weak measurements and interaction-free measurements has greatly expanded the conceptual and experimental toolbox to explore the quantum world. Here we demonstrate single-shot variable-strength weak measurements of the electron and nuclear spin states of a P31 single-atom donor in silicon. We first show how the partial collapse of the nuclear spin due to measurement can be used to coherently rotate the spin to a desired pure state. We explicitly demonstrate that phase coherence is preserved with high fidelity throughout multiple sequential single-shot weak measurements and that the partial state collapse can be reversed. Second, we use the relation between measurement strength and perturbation of the nuclear state as a physical meter to extract the tunnel rates between the P31 donor and a nearby electron reservoir from data conditioned on observing no tunneling events. Our experiments open avenues to measurement-based state preparation, steering and feedback protocols for spin systems in the solid state, and highlight the fundamental connection between information gain and state modification in quantum mechanics.QCD/Vandersypen La

Induction of mouse leukemia with purified nucleic acid preparations /

"Report Issued: October 14, 1957.""Submitted by: Stafford L. Warren, M.D.""Section Chief: Norman S. Simmons.""Section: Enzyme Chemistry.""Section Chief: Esther F. Hays.""Section: Hematology.""Division Chief: James F. Mead.""Division: Biochemistry.""Division Chief: Stafford L. Warren.""Division: Administrative and Technical Service.""90830-91130-00020."Includes bibliographical references (page 11).Contract No.Mode of access: Internet

The Laws of War and Public Opinion: An Experimental Study

Research examining whether the laws of war change state behavior has produced conflicting results, and limitations of observational studies have stalled progress on the topic. I have conducted a survey experiment to bring new evidence to the debate. I directly test whether a mechanism hypothesized to drive compliance with international law—public opinion—creates pressure to comply with the laws of war. The results provide qualified support to research suggesting that democracies may comply with the laws of war when there is the expectation of reciprocity, and demonstrate the potential of using experimental methods to study the laws of war

Measurement of the diffractive cross-section in deep inelastic scattering

Diffractive scattering of $\gamma^* p \to X + N$, where $N$ is either a proton or a nucleonic system with $M_N~<~4$~GeV has been measured in deep inelastic scattering (DIS) at HERA. The cross section was determined by a novel method as a function of the $\gamma^* p$ c.m. energy $W$ between 60 and 245~GeV and of the mass $M_X$ of the system $X$ up to 15~GeV at average $Q^2$ values of 14 and 31~GeV$^2$. The diffractive cross section $d\sigma^{diff} /dM_X$ is, within errors, found to rise linearly with $W$. Parameterizing the $W$ dependence by the form d\sigma^{diff}/dM_X \propto (W^2)^{(2\overline{\mbox{\alpha_{_{I\hspace{-0.2em}P}}}} -2)} the DIS data yield for the pomeron trajectory \overline{\mbox{\alpha_{_{I\hspace{-0.2em}P}}}} = 1.23 \pm 0.02(stat) \pm 0.04 (syst) averaged over $t$ in the measured kinematic range assuming the longitudinal photon contribution to be zero. This value for the pomeron trajectory is substantially larger than \overline{\mbox{\alpha_{_{I\hspace{-0.2em}P}}}} extracted from soft interactions. The value of \overline{\mbox{\alpha_{_{I\hspace{-0.2em}P}}}} measured in this analysis suggests that a substantial part of the diffractive DIS cross section originates from processes which can be described by perturbative QCD. From the measured diffractive cross sections the diffractive structure function of the proton F^{D(3)}_2(\beta,Q^2, \mbox{x_{_{I\hspace{-0.2em}P}}}) has been determined, where $\beta$ is the momentum fraction of the struck quark in the pomeron. The form F^{D(3)}_2 = constant \cdot (1/ \mbox{x_{_{I\hspace{-0.2em}P}}})^a gives a good fit to the data in all $\beta$ and $Q^2$ intervals with $a = 1.46 \pm 0.04 (stat) \pmComment: 45 pages, including 16 figure