3,297 research outputs found
Many-agent controlled teleportation of multi-qubit quantum information
We present a general idea to construct methods for multi-qubit quantum
teleportation between two remote parties with control of many agents in the
network. Our methods seem to be much simpler than the existing method proposed
recently (Phys. Rev. A {\bf 70}, 022329(2004)). We then demonstrate our idea by
using several different protocols of quantum key distribution, including Ekert
91 and the deterministic secure communication protocol raised by Deng and Long.Comment: This paper has been accepted for publication in Phys. Lett.
Cavity-based architecture to preserve quantum coherence and entanglement
Quantum technology relies on the utilization of resources, like quantum
coherence and entanglement, which allow quantum information and computation
processing. This achievement is however jeopardized by the detrimental effects
of the environment surrounding any quantum system, so that finding strategies
to protect quantum resources is essential. Non-Markovian and structured
environments are useful tools to this aim. Here we show how a simple
environmental architecture made of two coupled lossy cavities enables a switch
between Markovian and non-Markovian regimes for the dynamics of a qubit
embedded in one of the cavity. Furthermore, qubit coherence can be indefinitely
preserved if the cavity without qubit is perfect. We then focus on entanglement
control of two independent qubits locally subject to such an engineered
environment and discuss its feasibility in the framework of circuit quantum
electrodynamics. With up-to-date experimental parameters, we show that our
architecture allows entanglement lifetimes orders of magnitude longer than the
spontaneous lifetime without local cavity couplings. This cavity-based
architecture is straightforwardly extendable to many qubits for scalability.Comment: 12 pages, 9 figures, 1 table. To appear on Nature Scientific Report
Moderate deviations in Poisson approximation: a first attempt
Poisson approximation using Stein's method has been extensively studied in
the literature. The main focus has been on bounding the total variation
distance. This paper is a first attempt on moderate deviations in Poisson
approximation for right-tail probabilities of sums of dependent indicators. We
obtain results under certain general conditions for local dependence as well as
for size-bias coupling. These results are then applied to independent
indicators, 2-runs, and the matching problem.Comment: 21 page
Harnessing non-Markovian quantum memory by environmental coupling
Controlling the non-Markovian dynamics of open quantum systems is essential
in quantum information technology since it plays a crucial role in preserving
quantum memory. Albeit in many realistic scenarios the quantum system can
simultaneously interact with composite environments, this condition remains
little understood, particularly regarding the effect of the coupling between
environmental parts. We analyze the non-Markovian behavior of a qubit
interacting at the same time with two coupled single-mode cavities which in
turn dissipate into memoryless or memory-keeping reservoirs. We show that
increasing the control parameter, that is the two-mode coupling, allows for
triggering and enhancing a non-Markovian dynamics for the qubit starting from a
Markovian one in absence of coupling. Surprisingly, if the qubit dynamics is
non-Markovian for zero control parameter, increasing the latter enables
multiple transitions from non-Markovian to Markovian regimes. These results
hold independently on the nature of the reservoirs. This work highlights that
suitably engineering the coupling between parts of a compound environment can
efficiently harness the quantum memory, stored in a qubit, based on
non-Markovianity.Comment: 8 pages, 5 figures. To appear in Phys. Rev.
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