We investigate the generation of multipartite entangled state in a system of N quantum dots embedded in a microcavity and examine the emergence of genuine multipartite entanglement by three different characterizations...
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We investigate the generation of multipartite entangled state in a system of N quantum dots embedded in a microcavity and examine the emergence of genuine multipartite entanglement by three different characterizations of entanglement. At certain times of dynamical evolution one can generate multipartite entangled coherent exciton states or multiqubit W states by initially preparing the cavity field in a superposition of coherent states or the Fock state with one photon, respectively. Finally, we study environmental effects on multipartite entanglement generation and find that the decay rate for the entanglement is proportional to the number of excitons.
The power of sharing computation in a cryptosystem is crucial in several real-life applications of cryptography. Cryptographic primitives and tasks to which threshold cryptosystems have been applied include variants o...
We introduce the entanglement gauge describing the combined effects of local operations and nonlocal unitary transformations on bipartite quantum systems. The entanglement gauge exploits the invariance of nonlocal pro...
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We introduce the entanglement gauge describing the combined effects of local operations and nonlocal unitary transformations on bipartite quantum systems. The entanglement gauge exploits the invariance of nonlocal properties for bipartite systems under local (gauge) transformations. This new formalism yields observable effects arising from the gauge geometry of the bipartite system. In particular, we propose a non-Abelian gauge theory realized via two separated spatial modes of the quantized electromagnetic field manipulated by linear optics. In this linear optical realization, a bipartite state of two separated spatial modes can acquire a non-Abelian geometric phase.
Summary form only given. We develop a sufficiency criterion for quantum separability, valid for arbitrary states of two arbitrary systems. Our criterion confirms spin entanglement of two macroscopic atomic samples in ...
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Summary form only given. We develop a sufficiency criterion for quantum separability, valid for arbitrary states of two arbitrary systems. Our criterion confirms spin entanglement of two macroscopic atomic samples in experiments by Julsgaard, Kozhekin, and Polzik [Nature (2001)].
A set system (X,F) with X = {x1,..., xm) and F = {B1,..., Bn}, where Bi ⊆ X, is called an (n,m) cover-free set system (or CF set system) if for any 1 ≤ i, j, k ≤ n and j ≠ k, |Bi| ≥ 2 |Bj ∩ Bk| + 1. In this paper...
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Cheating detection in linear secret sharing is considered. The model of cheating extends the Tompa-Woll attack and includes cheating during multiple (unsuccessful) recovery of the secret. It is shown that shares in mo...
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The work investigates the design of ideal threshold secret sharing in the context of cheating prevention. We showed that each orthogonal array is exactly a defining matrix of an ideal threshold scheme. To prevent chea...
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We identify a broad class of physical processes in an optical quantum circuit that can be efficiently simulated on a classical computer: this class includes unitary transformations, amplification, noise, and measureme...
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We identify a broad class of physical processes in an optical quantum circuit that can be efficiently simulated on a classical computer: this class includes unitary transformations, amplification, noise, and measurements. This simulatability result places powerful constraints on the capability to realize exponential quantum speedups as well as on inducing an optical nonlinear transformation via linear optics, photodetection-based measurement, and classical feedforward of measurement results, optimal cloning, and a wide range of other processes.
We propose a feedback scheme for the production of two-mode spin squeezing. We determine a general expression for the optimal feedback, which is also applicable to the case of single-mode spin squeezing. The two-mode ...
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We propose a feedback scheme for the production of two-mode spin squeezing. We determine a general expression for the optimal feedback, which is also applicable to the case of single-mode spin squeezing. The two-mode spin squeezed states obtained via this feedback are optimal for j=1/2 and are very close to optimal for j>1/2. In addition, the master equation suggests a Hamiltonian that would produce two-mode spin squeezing without feedback, and is analogous to the two-axis countertwisting Hamiltonian in the single-mode case.
Summary form only given. We consider quantum teleportation and entanglement swapping for systems of arbitrary spin j /spl ges/ 1/2. Spin quantum teleportation and entanglement swapping enable quantum state transfer be...
Summary form only given. We consider quantum teleportation and entanglement swapping for systems of arbitrary spin j /spl ges/ 1/2. Spin quantum teleportation and entanglement swapping enable quantum state transfer between distant material systems, as well as being important for quantum network operations built on qubit elements. We identify an appropriate entangled resource state for high-fidelity spin quantum teleportation, and, in the case of spin entanglement swapping, develop a measurement scheme that yields the largest entanglement between the two output states. We present teleportation fidelity for moderate photon numbers and finite displacements. We show that the fidelity for teleportation of coherent spin states can be significantly improved using an alternative scheme of final rotations. Also the fidelity is not maximised for a maximally entangled entanglement resource, which is unusual in quantum teleportation. This teleportation scheme also exhibits entanglement swapping for moderate photon numbers. In contrast with the case for the fidelity, the final entanglement is maximised when the entanglement resource is maximally entangled.
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