16125330
Pattern formation in quantum Turing machines
We investigate the iteration of a sequence of local and pair unitary transformations, which can be interpreted to result from a Turing-head $(\mathrm{pseudospin}S)$ rotating along a closed Turing tape $(M$ additional pseudospins). The dynamical evolution of the Bloch vector of S, which can be decomposed into ${2}^{M}$ primitive pure state Turing-head trajectories, gives rise to fascinating geometrical patterns reflecting the entanglement between head and tape. These machines thus provide intuitive examples for quantum parallelism and, at the same time, means for local testing of quantum network dynamics.
14854411
Correlation between Correlations: Process and Time in Quantum Networks
We study a special inhomogeneous quantum network consisting of a ring of M pseudo-spins (here M = 4) sequentially coupled to one and the same central spin under the influence of given pulse sequences (quantum gate operations). This architecture could be visualized as a quantum Turing machine with a cyclic "tape". Rather than input-output-relations we investigate the resulting process, i.e. the correlation between one-and two-point expectation values ("correlations") over various time-steps. The resulting spatiotemporal pattern exhibits many non-classical features including Zeno-effects, violation of temporal Bell-inequalities and quantum parallelism. Due to the strange web of correlations being built-up, specific measurement outcomes for the tape may refer to one or several preparation histories of the head. Specific families of correlation functions are more stable with respect to dissipation than the total wave-function.
18424039
Quantum control of atomic systems by time resolved homodyne detection
We describe the light-matter interaction of a single two level atom with the electromagnetic vacuum in terms of field and dipole variables by considering homodyne detection of the emitted fields. Spontaneous emission is then observed as a continuous fluctuating force acting on the atomic dipole. The effect of this force may be compensated and even reversed by feedback.
15461480
Moving Quantum Agents in a Finite Environment
We investigate an all-quantum-mechanical spin network, in which a subset of spins, the K “moving agents”, are subject to local and pair unitary transformations controlled by their position with respect to a fixed ring of M “environmental”-spins. We demonstrate that a “flow of coherence” results between the various subsystems. Despite entanglement between the agents and between agent and environment, local (non-linear) invariants may persist, which then show up as fascinating patterns in each agent’s Bloch-sphere. Such patterns disappear, though, if the agents are controlled by different rules. Geometric aspects thus help to understand the interplay between entanglement and decoherence.
37474263
Quantum control by compensation of quantum fluctuations.
We show that the influence of quantum fluctuations in the electromagnetic field vacuum on a two level atom can be measured and consequently compensated by balanced homodyne detection and a coherent feedback field. This compensation suppresses the decoherence associated with spontaneous emissions for a specific state of the atomic system allowing complete control of the coherent state of the system.
17564383
Measurement models for time-resolved spectroscopy: a comment
We present an exactly solvable model for photon emission, which allows us to examine the evolution of the photon wavefunction in space and time. We apply this model to coherent phenomena in three-level systems with a special emphasis on the effects of the photon detection process.
110745619
RHIC 10 Hz global orbit feedback system
Vibrations of the cryogenic triplet magnets at the Relativistic Heavy Ion Collider (RHIC) are suspected to be causing the horizontal beam perturbations observed at frequencies around 10 Hz. Several solutions to counteract the effect have been considered in the past, including a local beam feedback system at each of the two experimental areas, reinforcing the magnet base support assembly, and a mechanical servo feedback system. However, the local feedback system was insufficient because perturbation amplitudes outside the experimental areas were still problematic, and the mechanical solutions are very expensive. A global 10 Hz orbit feedback system consisting of 36 beam position monitors (BPMs) and 12 small dedicated dipole corrector magnets in each of the two 3.8 km circumference counter-rotating rings has been developed and commissioned in February 2011. A description of the system architecture and results with beam will be discussed.
32903269
Coherent electron cooling demonstration experiment
Coherent electron cooling (CEC) has a potential to significantly boost luminosity of high-energy, high-intensity hadron-hadron and electron-hadron colliders. In a CEC system, a hadron beam interacts with a cooling electron beam. A perturbation of the electron density caused by ions is amplified and fed back to the ions to reduce the energy spread and the emittance of the ion beam. To demonstrate the feasibility of CEC we propose a proof-of-principle experiment at RHIC using SRF linac. In this paper, we describe the setup for CeC installed into one of RHIC's interaction regions. We present results of analytical estimates and results of initial simulations of cooling a gold-ion beam at 40 GeV/u energy via CeC. We plan to complete the program in five years. During first two years we will build coherent electron cooler in IP2 of RHIC. In parallel we will develop complete package of computer simulation tools for the start-to-end simulation predicting exact performance of a CeC. The later activity will be the core of Tech X involvement into the project. We will use these tools to predict the performance of our CeC device. The experimental demonstration of the CeC will be undertaken in years three to five ofmore » the project. The goal of this experiment is to demonstrate the cooling of ion beam and to compare its measured performance with predictions made by us prior to the experiments.« less
40825691
SNS Ring Injection Stripped Electron Collection: Design Analysis and Technical Issues
This paper describes the simulation studies on the motions of stripped electrons generated in the injection section of the Spallation Neutron Source (SNS) accumulator ring and the effective collection mechanism. Such studies are important for high intensity machines, in order to reduce beam loss and protect other components in the vicinity. The magnetic field is applied to guide electrons to a collector, which is located at the bottom of the beam vacuum chamber. Part of the study results with and without considering the interactions between electrons and materials are presented and discussed. The final engineering design of the electron collector (catcher) Is also described.