We propose a new scheme to generate multi-photon entanglement in two steps. First, we utilize a superconductor to create multi-quantum-dot entanglement; secondly, we use the input photon to transfer it into multi-photon entanglement. Moreover, the maximum probability for the swap of photon and quantum-dot qubits is close to unity for a single input Gaussian photon. More importantly, by mapping the multi-quantum-dot state into coherent states of oscillators, such as cavity modes, the multi-quantum-dot entanglement in our scheme can be protected from the decoherence induced by the noise. Thus, it is possible to generate more than eight spatially separated entangled photons in the realistic experimental conditions.
We propose a method for deterministic generation of entanglement between a quantum-dot spin and a photon. Entanglement is established by an elastic scattering event from a cavity that is strongly coupled to a singly charged quantum dot. Due to the elastic nature of the interaction, the energy of the photon does not become entangled with the quantum dot, eliminating the need for temporal postselection. We derive an analytical expression for fidelity of the generated entangled state and investigate its behavior under realistic experimental conditions. We show that entanglement fidelities exceeding 0.974 can be realized using currently achievable quantum-dot cavity quantum electrodynamics systems.
We theoretically investigate fast and highly efficient entangled-photon generation by irradiating a quantum dot (QD) embedded in a microcavity with short laser pulses. We evaluate the optimized width and field strength of the pulses for achieving a high population of an excited state as an entangled-photon source. We also calculate the emission time of the entangled photon pair as a function of the cavity quality factor
Q. The shortest emission time reaches
3/(4g) under the condition $Q={\ensuremath{\omega}}_{0}/(4g)$, where
g is the coupling frequency between the cavity photon and excited states of the QD and ${\ensuremath{\omega}}_{0}$ is the excitation frequency of the QD. The QD-cavity system has a potential for fast and efficient generation of high-quality entangled-photon pairs.