Quantum information processing using quantum dot spins and cavity-QED

Quantum information processing using quantum dot spins and cavity-QED

February 1, 2008 | A. Imamoglu, D. D. Awschalom, G. Burkard, D. P. DiVincenzo, D. Loss, M. Sherwin, A. Small
This paper proposes a quantum information processing scheme using quantum dot (QD) electron spins coupled through a microcavity mode. The scheme leverages the long-range interaction mediated by a high-finesse microcavity and Raman transitions induced by classical laser fields. This allows for parallel controlled-not (CNOT) operations and arbitrary single-qubit rotations. The scheme is scalable to more than 100 qubits, as semiconductor QDs can be embedded in microdisk structures with long spin coherence times. The proposed scheme uses a single cavity mode and laser fields to mediate coherent interactions between distant QD spins. The key elements include Raman coupling of spin states via strong laser fields and a single-mode microcavity. The effective Hamiltonian describes the interaction between QD spins and the cavity mode, enabling two-qubit operations. The scheme allows for parallel quantum logic operations and can be used to implement a conditional phase-flip (CPF) gate, which is a key component of a controlled-not gate. The time required for a two-qubit gate operation is limited by the strength of the electron-hole-cavity coupling. The scheme also includes a method for measuring the spin state of each qubit using laser fields to realize exact two-photon resonance with the cavity mode. The primary technological limitation is the short photon lifetime in state-of-the-art microcavities, which can be improved using new processing techniques or ultra-high finesse cavities. The scheme is scalable and can be used for quantum computation with long spin coherence times. The paper also discusses the feasibility of the scheme, including the decoherence rates and the potential for parallel operations. The proposed scheme is based on the use of all-optical Raman transitions to couple two conduction-band spin states, enabling the combination of ultra-long spin coherence times with fast, long-distance, parallel optical switching. The scheme is compared to other quantum computing schemes and is shown to be a promising approach for quantum information processing.This paper proposes a quantum information processing scheme using quantum dot (QD) electron spins coupled through a microcavity mode. The scheme leverages the long-range interaction mediated by a high-finesse microcavity and Raman transitions induced by classical laser fields. This allows for parallel controlled-not (CNOT) operations and arbitrary single-qubit rotations. The scheme is scalable to more than 100 qubits, as semiconductor QDs can be embedded in microdisk structures with long spin coherence times. The proposed scheme uses a single cavity mode and laser fields to mediate coherent interactions between distant QD spins. The key elements include Raman coupling of spin states via strong laser fields and a single-mode microcavity. The effective Hamiltonian describes the interaction between QD spins and the cavity mode, enabling two-qubit operations. The scheme allows for parallel quantum logic operations and can be used to implement a conditional phase-flip (CPF) gate, which is a key component of a controlled-not gate. The time required for a two-qubit gate operation is limited by the strength of the electron-hole-cavity coupling. The scheme also includes a method for measuring the spin state of each qubit using laser fields to realize exact two-photon resonance with the cavity mode. The primary technological limitation is the short photon lifetime in state-of-the-art microcavities, which can be improved using new processing techniques or ultra-high finesse cavities. The scheme is scalable and can be used for quantum computation with long spin coherence times. The paper also discusses the feasibility of the scheme, including the decoherence rates and the potential for parallel operations. The proposed scheme is based on the use of all-optical Raman transitions to couple two conduction-band spin states, enabling the combination of ultra-long spin coherence times with fast, long-distance, parallel optical switching. The scheme is compared to other quantum computing schemes and is shown to be a promising approach for quantum information processing.
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