Quantum Teleportation Between Cities Moves Closer with New Hardware Blueprint

Scientists at Delft University of Technology, including Soubhadra Maiti, Guus Avis and Sounak Kar, have delved into the intricate requirements for teleportation within an intercity quantum network. Their research, co-led by Stephanie Wehner, addresses the hardware prerequisites needed to achieve a fidelity level that matches classical limits in such networks. By formulating optimisation problems and deriving analytical expressions based on simplified noise models, they explore how different hardware configurations can impact teleportation fidelity and rates. The study highlights the potential for current technology to support metropolitan-scale teleportation but identifies necessary enhancements for intercity applications. Their work not only advances our understanding of quantum communication networks but also provides a roadmap for future technological developments in this field.

Analytical modelling of fidelity and rate for intercity quantum teleportation reveals significant challenges to practical implementation

Scientists have identified the minimal hardware improvements needed to achieve quantum teleportation across intercity distances. This work details the requirements for an end-to-end expected teleportation fidelity of 2/3, representing the classical limit for reliable quantum communication. Researchers formulated the problem as an optimisation task, using hardware parameters as variables to determine the necessary device capabilities.
Closed-form analytical expressions were derived for teleportation fidelity and rate, accounting for heterogeneous hardware including quantum repeater chains with memory limitations. These derivations are based on the timing of link generation within both metropolitan networks and the long-distance backbone, and were validated using simulations on the NetSquid platform.

The resulting analytical expressions allow for efficient exploration of potential hardware configurations without relying on computationally intensive simulations. Applying this framework to a representative network, utilising trapped-ion processors for metropolitan nodes and ensemble-based memories for the backbone, reveals that teleportation is currently achievable across metropolitan distances when data qubits are prepared after entanglement is established.

However, extending this capability to intercity scales necessitates further, yet plausible, advancements in hardware performance. The study demonstrates that metropolitan-scale teleportation can be achieved with existing technology, while intercity communication requires specific, quantifiable improvements.

This research provides a clear pathway for developing the hardware needed to build a functional intercity quantum network, facilitating applications ranging from secure communication to distributed quantum computing. The analytical framework developed offers a valuable tool for optimising network design and assessing the feasibility of future quantum communication infrastructure.

Analytical derivation and validation of fidelity for heterogeneous quantum teleportation networks are presented herein

A formulation of hardware requirements computation as optimisation problems underpins this work, utilising hardware parameters as decision variables. The study investigates teleportation within an intercity-scale network, comprising two metropolitan-scale networks linked by a long-distance backbone, aiming to identify minimal improvements needed to achieve an end-to-end expected teleportation fidelity of 2/3, representing the classical limit.

Closed-form analytical expressions were derived for teleportation fidelity and rate, assuming a simplified noise model and heterogeneous hardware, including a chain with a memory cut-off. These derivations are based on events defined by the order statistics of link generation durations in both the metropolitan networks and the backbone, allowing efficient exploration of the optimisation parameter space without computationally intensive simulations.

The analytical expressions were validated through simulations performed on the NetSquid platform, confirming their accuracy and predictive power. A representative realisation was then analysed, employing trapped-ion processors for metropolitan nodes and ensemble-based memories for the backbone, to assess current capabilities and identify necessary enhancements.

Results indicate that teleportation across metropolitan distances is currently achievable when the data qubit is prepared after end-to-end entanglement is established. Extending teleportation to intercity scales, however, necessitates additional improvements in hardware performance, though these are considered plausibly attainable.

The methodology also facilitates the evaluation of performance metrics for heterogeneous networks, offering independent value beyond the primary optimisation task. This research builds upon prior studies of quantum repeater chains, focusing on key contributions relevant to inhomogeneous networks where node distances vary.

Hardware limitations for intercity quantum teleportation fidelity and rate are significant challenges to overcome

Teleportation fidelity of 2/3 represents the classical limit and is achievable across metropolitan distances with current hardware when the data qubit is prepared after end-to-end entanglement establishment. Extending teleportation to intercity scales, however, necessitates further improvements in hardware performance.

This work investigates the hardware requirements for teleportation within an intercity-scale network topology comprising two metropolitan-scale networks connected by a long-distance backbone link. The study formulates hardware requirements computation as optimisation problems, utilising hardware parameters as decision variables.

Closed-form analytical expressions for teleportation fidelity and rate were derived assuming a simplified noise model and heterogeneous hardware, including a chain with a memory cut-off. These derivations are based on order statistics of link generation durations in both metropolitan networks and the backbone, and were validated through simulations on the NetSquid platform.

The analytical expressions enable efficient exploration of the optimisation parameter space, circumventing computationally intensive simulations. A representative realisation was considered, employing trapped-ion processors for metropolitan nodes and ensemble-based memories for the backbone. Results indicate that achieving a teleportation fidelity of 2/3 is feasible with existing technology for metropolitan distances.

Extending this to intercity scales requires additional, yet plausible, advancements in hardware capabilities. The network architecture examined consists of four components: user-controlled end nodes, metropolitan hubs, border nodes forming the backbone, and individual repeater nodes within the backbone, spanning a total distance of 450km. Each end node is connected to its nearest hub 25km away, forming the metropolitan networks.

Hardware thresholds for practical quantum teleportation across metropolitan and long-distance links remain a significant challenge

Researchers have determined the minimal hardware improvements necessary to achieve classical-limit fidelity for quantum teleportation across an intercity network. This investigation focused on a network topology comprising two metropolitan-scale networks connected by a long-distance backbone, identifying requirements beyond current capabilities.

The work formulates hardware optimisation problems, utilising device capabilities as variables to compute teleportation fidelity and rate. Analytical expressions were derived for teleportation fidelity and rate in heterogeneous networks, including those with memory limitations, based on the timing of link generation events.

These expressions were validated using simulations on the NetSquid platform, allowing for efficient exploration of optimisation parameters without intensive computation. Applying this framework to a network with trapped-ion processors in metropolitan areas and ensemble-based memories for the backbone revealed that metropolitan teleportation is currently achievable with existing hardware, provided end-to-end entanglement is established beforehand.

Extending this to intercity scales, however, necessitates further improvements in hardware performance. The derived analytical expressions are valuable for evaluating performance metrics in heterogeneous quantum networks, representing an independent contribution beyond the specific teleportation study.

The authors acknowledge limitations inherent in the simplified noise model employed, and future research could explore more complex noise characteristics. Further work may also investigate the impact of different network topologies and hardware configurations on teleportation performance, potentially refining the identified hardware requirements and paving the way for practical, long-distance quantum communication.

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