Abstract
Inspired by recent developments in the control and manipulation of quantum dot nuclear spins, which allow for the transfer of an electron spin state to the surrounding nuclear-spin ensemble for storage, we propose a quantum repeater scheme that combines individual quantum dot electron spins and nuclear-spin ensembles, which serve as spin-photon interfaces and quantum memories respectively. We consider the use of low-strain quantum dots embedded in high-cooperativity optical microcavities. Quantum dot nuclear-spin ensembles allow for the long-term storage of entangled states, and heralded entanglement swapping is performed using cavity-assisted gates. We highlight the advances in quantum dot technologies required to realize our quantum repeater scheme which promises the establishment of high-fidelity entanglement over long distances with a distribution rate exceeding that of the direct transmission of photons.
Highlights
The establishment of a quantum internet [1,2,3] is required to realize many promising applications of quantum science including long-distance quantum key distribution [4], dense coding [5, 6], and distributed quantum computing [7]
We propose the use of cavity-assisted photon scattering (CAPS)-based gates because the quantum dots (QDs) can be separated by several hundred nanometers [63], whereas performing the gate via the electric dipolar interaction [18] requires that the QDs be situated relatively close together, around 20 nm
We propose the use of photonic crystal (PhC) waveguides as they can be naturally incorporated with PhC cavities and offer a scalable platform which could lead to on-chip implementations [104]
Summary
The establishment of a quantum internet [1,2,3] is required to realize many promising applications of quantum science including long-distance quantum key distribution [4], dense coding [5, 6], and distributed quantum computing [7]. Single electron spins confined in quantum dots (QDs) offer fast initialization times, optical manipulation, and provide a promising route towards scalable quantum devices with a large number of qubits. The first is to mitigate the unwanted effects via decoupling techniques, or possibly by using QDs fabricated from isotopically purified II-VI materials [18] These methods could extend the coherence time of the electron spins, such that it is natural to ask if they could be used as both communication qubits and quantum memories. The notion of long storage times in such a scalable system has led to several proposals for quantum memories based on QD nuclear spin ensembles [39,40,41].
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