Comparative photoemission study of Bi2(Sr, Ca)3Cu2O8+y and Bi1.7Pb0.3Sr2Ca2Cu3O10+y

Wang, Nan-Lin; Wang, Yugui; Ji, Mingrong; Liu, Xianming

doi:10.1007/bf01323724

Cited by 76 publications

(102 citation statements)

References 16 publications

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“…Though a rigorous mathematical foundation for nested UDD is still under development [19,25], the success of threelayer UDD demonstrated here in two-qubit systems further strengthens the view that nested UDD can be a good strategy for decoherence suppression. Our approach can also be extended to protect an unknown superposition of two known basis states in an arbitrary multi-level system.…”

Section: Discussionmentioning

confidence: 77%

“…Note however, though this is a natural assumption and Ref. [15] reasoned about the smoothness of analogous UDDreduced effective Hamiltonians, some counter examples might exist [19]. With this smoothness assumption exercised with caution, we now introduce a second UDD layer to lock the second diagonal property Tr[ρ(t)| ↓↓ ↓↓ |].…”

Section: Protecting Unknown Two-qubit Entangled States By Nestedmentioning

confidence: 99%

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Protecting unknown two-qubit entangled states by nesting Uhrig’s dynamical decoupling sequences

et al. 2010

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Future quantum technologies rely heavily on good protection of quantum entanglement against environment-induced decoherence. A recent study showed that an extension of Uhrig's dynamical decoupling (UDD) sequence can (in theory) lock an arbitrary but known two-qubit entangled state to the N th order using a sequence of N control pulses [Mukhtar et al., Phys. Rev. A 81, 012331 (2010)]. By nesting three layers of explicitly constructed UDD sequences, here we first consider the protection of unknown two-qubit states as superposition of two known basis states, without making assumptions of the system-environment coupling. It is found that the obtained decoherence suppression can be highly sensitive to the ordering of the three UDD layers and can be remarkably effective with the correct ordering. The detailed theoretical results are useful for general understanding of the nature of controlled quantum dynamics under nested UDD. As an extension of our three-layer UDD, it is finally pointed out that a completely unknown two-qubit state can be protected by nesting four layers of UDD sequences. This work indicates that when UDD is applicable (e.g., when environment has a sharp frequency cut-off and when control pulses can be taken as instantaneous pulses), dynamical decoupling using nested UDD sequences is a powerful approach for entanglement protection.

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Section: Discussionmentioning

confidence: 77%

Section: Protecting Unknown Two-qubit Entangled States By Nestedmentioning

confidence: 99%

Protecting unknown two-qubit entangled states by nesting Uhrig’s dynamical decoupling sequences

et al. 2010

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“…Meanwhile, the minimum tool wear ratio was less than 1 %. Wang et al [8,9] reported that both rough and finish machining could be performed on the same machine by combining traditional EDM with high-speed arc discharge milling. Recent research showed that a high efficiency and greatly improving machined surface integrity could be achieved by combining negative tool polarity and positive tool polarity BEAM [10].…”

Section: Introductionmentioning

confidence: 99%

Observation and modeling research of high-velocity flushing effect on the performance of BEAM

Zhang

Chen

et al. 2015

Int J Adv Manuf Technol

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Blasting erosion arc machining (BEAM) is a novel high efficiency electrical erosion process, which is characterized by a powerful multi-hole inner flushing. In order to study the influence of the high-velocity flushing on the performance of BEAM, a single discharge experiment is carried out on a specially designed observation apparatus, and the phenomena that occurred during the discharge is observed using a high-speed video camera. During the discharge process, a spray cloud of the removed debris near the downstream side of the discharging point is captured by the camera. Tail shaped crater and erosion-corrosion features are also found on the workpiece and electrode surfaces, respectively. These observed phenomena imply that the high-velocity flushing can greatly improve the melting metal removal from the molten pool thereby improving the material removal rate (MRR). For purpose of exploring the mechanism behind, the flow field and pressure distribution of the high-velocity flushing are analyzed by using computational fluid dynamic (CFD) method. The analyzed results indicate that a low-pressure suction effect exists on the downstream side of the electrodes. With the help of the low-pressure suction effect, the high-velocity flushing can continuously take the molten metal out of the molten pool during the discharge, resulting in the reduction of the overheating of the molten metal and improve the efficiency of Fawang Zhang the discharging energy. Thereby, the work in this paper helps to explain why the high-velocity flushing can markedly promote the material removal rate.

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“…Note that the above sequence is by no means uniquely suited for the tasks PS1 and PS2. For example, sequences based on Hadamard arrays [60,61] or products of σ z Pauli matrices [62] can also be envisioned when the system is a collection of n q qubits (D S = 2 nq ). Nonetheless, the sequence of σ DS operators described here is notable since it requires a single pulse type.…”

Section: Complete Pointer Basismentioning

confidence: 99%

Pointer states via engineered dissipation

2011

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Pointer states are long-lasting high-fidelity states in open quantum systems. We show how any pure state in a non-Markovian open quantum system can be made to behave as a pointer state by suitably engineering the coupling to the environment via open-loop periodic control. Engineered pointer states are constructed as approximate fixed points of the controlled open-system dynamics, in such a way that they are guaranteed to survive over a long time with a fidelity determined by the relative precision with which the dynamics is engineered. We provide quantitative minimumfidelity bounds by identifying symmetry and ergodicity conditions that the decoherence-inducing perturbation must obey in the presence of control, and develop explicit pulse sequences for engineering any desired set of orthogonal states as pointer states. These general control protocols are validated through exact numerical simulations as well as semi-classical approximations in realistic single-and two-qubit dissipative systems. We also examine the role of control imperfections, and show that while pointer-state engineering protocols are highly robust in the presence of systematic pulse errors, the latter can also lead to unintended pointer-state generation in dynamical decoupling implementations, explaining the initial-state selectivity observed in recent experiments.

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Comparative photoemission study of Bi2(Sr, Ca)3Cu2O8+y and Bi1.7Pb0.3Sr2Ca2Cu3O10+y

Cited by 76 publications

References 16 publications

Protecting unknown two-qubit entangled states by nesting Uhrig’s dynamical decoupling sequences

Protecting unknown two-qubit entangled states by nesting Uhrig’s dynamical decoupling sequences

Observation and modeling research of high-velocity flushing effect on the performance of BEAM

Pointer states via engineered dissipation

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