Protocols for long-distance quantum communication with single ¹⁶⁷Er ions

Abstract

We design a quantum repeater architecture using individual 167Er ions doped into Y2SiO5 crystal. This ion is a promising candidate for a repeater protocol because of its long hyperfine coherence time in addition to its ability to emit photons within the telecommunication wavelength range. To distribute entanglement over a long distance, we propose two different swapping gates between nearby ions using the exchange of virtual cavity photons and the electric dipole–dipole interaction. We analyze their expected performance, and discuss their strengths and weaknesses. Then, we show that a post-selection approach can be implemented to improve the gate fidelity of the virtual photon exchange scheme by monitoring cavity emission. Finally, we use our results for the swapping gates to estimate the end-to-end fidelity and distribution rate for the protocol.

Key Device and Materials Specifications for a Repeater Enabled Quantum Internet

“…We will now lay out a model to evaluate a functional link comprised of the components outlined earlier and estimate the average time to connect (alternatively, rate of connection) as a performance metric. Asadi et al [27] give a relationship for the average time ( ) it takes to create a repeater enabled quantum link of total length L and an inter-repeater distance of L0:…”

“…In our simulations we identify an optimal 0 (to the nearest km) for a given set of parameter values that balances these two losses to maximize the data rate. The operation loss depends on the form of , for example, the model that we use is based on a modified Barrett-Kok scheme [27], which involves measurement of both qubits giving = ( ) 2 -the scheme is robust against photon loss and is a representative example of a probabilistic entanglement swapping operation. Furthermore, the rate at which we can create such links is also limited by the loss of fidelity from all the operations.…”

“…Furthermore, the rate at which we can create such links is also limited by the loss of fidelity from all the operations. As in [27] an estimate on the end-to-end fidelity can be obtained using the product of individual operations' fidelities: 2m qubit initializations (…”

“…In this work we present a codesign perspective for quantum repeaters. Building on existing models ( [4], [27], [28]), and modifying the analysis for real world performance of solid state qubit platforms, we lay out a modular framework that evaluates attainable data rates for a QR enabled quantum link as a function of various material and device parameters of interest. This approach is then used to outline benchmarks based on demonstrated properties of materials and devices.…”

“…We use a first generation, heralded quantum communication model (that we believe has the most potential for successful deployment in the shorter term; described in SI) for our estimates and adapt a recently proposed scheme [27] for analysis. Many of these principles and discussion directly map across qubit platforms and can be a straightforward extension to other systems.…”