Quantum networking, a crucial part of the second quantum revolution, uses quantum nodes to enhance quantum computing power. The Gottesman-Kitaev-Preskill (GKP) bosonic error correcting code is considered the future of quantum communication due to its resilience to photon loss. Quantum networking is facilitated by quantum repeaters and switches, which can forward quantum data efficiently despite photon loss and thermal noise. Recent research proposes quantum repeaters based on the GKP code, and introduces a quantum switch for GKP-qubit-based entanglement distribution networks. This could significantly impact the future of quantum communication and networking.
What is the Future of Quantum Networks?
Quantum networking is a key aspect of the ongoing second quantum revolution. It involves the use of quantum nodes, which are interconnected small, finite-sized quantum logic units, to scale up quantum computing power. These nodes are implemented using light, with the various degrees of freedom of single photons, such as polarization, time-bin, or spatio-spectrotemporal mode, providing means to encode quantum information in light.
However, the Gottesman-Kitaev-Preskill (GKP) bosonic error correcting code, which is known to be resilient to photon loss, is seen as the future of quantum communication. This is because GKP-encoded qubits have been shown to nearly achieve the quantum communication capacity of Gaussian thermal-loss channels under mean photon number constraint. These channels model most common transmission media such as optical fiber and free-space links.
How Do Quantum Repeaters and Switches Work?
Quantum networking with light is enabled by specialized helper nodes known as quantum repeaters and quantum switches. These consist of quantum optical sources and detectors, quantum memories, and fast optical switches. They can forward quantum data reliably in the face of photon loss and thermal noise, and do so efficiently at rates above direct transmission.
Quantum repeaters are line elements connecting two clients, which could be end users or other repeaters or switches. Quantum switches, on the other hand, have the additional ability to switch between or connect multiple clients. Together, they can be used to realize quantum networks of arbitrary topology at different distance scales.
What is the Role of the GKP Code in Quantum Networking?
Quantum repeaters based on the GKP code have been proposed and analyzed recently. The most notable among these is the repeater of Ref 26, which enables high entanglement rates. Its architecture involves the use of multiplexed copies of physical-logical GKP qubit resource Bell states. The logical qubit part is retained at the repeater, serving as an all-photonic quantum memory, while the physical qubit part is transmitted towards a neighboring node for interfacing via physical-physical GKP qubit Bell state measurement (BSM).
How Does the Quantum Switch Work?
In this paper, the authors introduce and analyze a quantum switch for GKP-qubit-based entanglement distribution networks. The architecture of this switch is compatible with that of the repeater of Ref 26, involving the same multiplexed physical-logical GKP-qubit-based entangled resource states. The switch facilitates entanglement distribution between pairs of its clients, which may most generally be at different distances.
What is the Potential Impact of this Research?
The authors illustrate their results for an exemplary data center network, where the data center is a client of a switch and all of its other clients aim to connect to the data center alone. This scenario also captures the general case of a gateway router connecting a local area network to a global network. This research provides a way to realize quantum networks of arbitrary topology, which could have significant implications for the future of quantum communication and networking.
An article titled “Quantum Switches for Gottesman-Kitaev-Preskill Qubit-based All-Photonic Quantum Networks” was published on February 4, 2024. The authors of this article are Mohadeseh Azari, P. Polakos, and Kaushik P. Seshadreesan. The article was sourced from arXiv, a repository maintained by Cornell University. The article can be accessed through its DOI reference: https://doi.org/10.48550/arxiv.2402.02721.
