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Physical Review A

Voltage-controlled entanglement and quantum-information transfer between spatially separated quantum-dot molecules

Xin‐You Lü, Jing Wu, Lili Zheng, Zhiming Zhan

Published Apr 4, 2011• 47 citations
Publisher

Abstract

We propose two schemes for generating entanglement and quantum-state transfer (QST) between two spatially separated semiconductor quantum dot molecules (QDMs) based on voltage-controlled tunneling effects. In the present schemes, two QDMs are trapped in two spatially separated cavities connected by a fiber. By numerically simulating the evolution of the system, we show that the generation of entanglement and QST can be controlled by an external gate voltage in our schemes. Moreover, proposed schemes are robust against the noise of system parameters.

DOI
10.1103/physreva.83.042302

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We propose two schemes for generating entanglement and quantum-state transfer (QST) between two spatially separated semiconductor quantum dot molecules (QDMs) based on voltage-controlled tunneling effects. In the present schemes, two QDMs are trapped in two spatially separated cavities connected by a fiber. By numerically simulating the evolution of the system, we show that the generation of entanglement and QST can be controlled by an external gate voltage in our schemes. Moreover, proposed schemes are robust against the noise of system parameters.
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Voltage-controlled quantum dynamics of two quantum-dot molecules (QDMs) embedded in two separated photonic crystal cavities are theoretically investigated. We show numerically that generation of entangled states and population transfer between the two QDMs can be realized with the same coupling parameters. The effects of parameters deviation and dissipations on generation entangled states and populations transfer are also discussed. The results may be used for realization of new-type of solid state quantum devices and integrated electro-optical devices.
An alternative voltage-controlled scheme is proposed for the generation of an N-qubit W state with distant self-assembled semiconductor quantum dot molecules (QDMs) via adiabatic-varying tunnel coupling. The N semiconductor QDMs are trapped in N spatially separated cavities coupled with N−1 fibers. The present scheme takes full advantage of adiabatic passage and the exceptional features of semiconductor QDMs. The decoherence caused by the excited state spontaneous emission and the fiber loss was efficiently suppressed. In addition, our calculations show that the present scheme is robust against the deviation of the parameters.
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Currently there is strong interest in realizing implementations of quantum computation and quantum cryptography in a solid state environment. One of the systems that are actively studied are semiconductor quantum dots (QDs). Due to their discrete energy level structure, they are often called artificial atoms, and they attract immediately interest of quantum information science since they allow to mimic the design developed for atomic physics systems such as ions in traps or atoms in cavities. However, despite of the similarities, one has to keep in main that any elementary excitation in a QD has a generic many-body character. An essential building block of a quantum processor is a quantum gate which entangles the states of two quantum bits. Recently it has been proposed that a pair of vertically aligned QDs could be used as an optically driven quantum gate: The quantum bits are individual carriers either on dot zero or dot one. The different dot indices play the same role as a "spin," therefore we term them "isospin." Quantum mechanical tunneling between the dots rotates the "isospin" and leads to superposition of two quantum dot states. The quantum gate is built when two different particles, an electron and a hole, are created optically. The two particles form entangled isospin states. The entanglement can be controlled by application of an electric field along the heterostructure growth direction. Here we present spectroscopic studies on single quantum dot molecules (QDMs) with different vertical separation between the dots that support the feasibility of this proposal. The comparison of the evolution of the excitonic recombination spectrum with the results of calculations allows us to demonstrate coherent tunneling of electrons and holes across the separating barrier and the formation of entangled exciton states. For a given barrier width, we find only small variations of the tunneling induced splitting between the entangled states demonstrating a good homogeneity within the obtained QDM ensembles.
We propose a new scheme for realizing deterministic quantum state transfer (QST) between two spatially separated single molecule magnets (SMMs) with the framework of cavity quantum electrodynamics (QED). In the present scheme, two SMMs are trapped in two spatially separated optical cavities coupled by an optical fiber. Through strictly numerically simulating, we demonstrate that our scheme is robust with respect to the SMMs' spontaneous decay and fiber loss under the conditions of dispersive SMMs-field interaction and strong coupling of cavity fiber. In addition, we also discuss the influence of photon leakage out of cavities and show that our proposal is good enough to demonstrate the generation of QST with high fidelity utilizing the current experimental technology. The present investigation provides research opportunities for realizing QST between solid-state qubits and may result in a substantial impact on the progress of solid-state-based quantum communications network.