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Physical Review A

Quantum routing based on chiral state transfer in arbitrary N -node networks

Wei Feng, Zuyan Wei, Guo-Qiang Zhang, Junyao Li, Junxiang Zhang, Chui‐Ping Yang

Published Apr 18, 2025• 2 citations
Publisher

Abstract

The ability to route quantum states between arbitrary nodes in a multinode network is one of the many facets required to build future large-scale quantum computing devices. Quantum routing can be implemented based on chiral dynamics, while their related research stays in three-node networks. In this paper, we give the target Hamiltonian for realizing chiral dynamics in arbitrary $N$-node networks. Based on the derived Hamiltonian, we present key features of chiral state transfer in multinode spin and bosonic networks. For the realistic implementation of the required Hamiltonian, we propose a modulation scheme to generate the matched effective Floquet Hamiltonian. Furthermore, we numerically simulate the multinode chiral dynamics with realistic parameters in superconducting circuits, and the results clearly show multinode chiral state transfer. Our work provides a universal and fundamental framework for understanding chiral dynamics in multinode networks. These findings will stimulate quantum state transfer, quantum routing, and nonreciprocal circulators in multinode networks.

DOI
10.1103/physreva.111.042423

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The ability to route quantum states between arbitrary nodes in a multinode network is one of the many facets required to build future large-scale quantum computing devices. Quantum routing can be implemented based on chiral dynamics, while their related research stays in three-node networks. In this paper, we give the target Hamiltonian for realizing chiral dynamics in arbitrary NNN-node networks. Based on the derived Hamiltonian, we present key features of chiral state transfer in multinode spin and bosonic networks. For the realistic implementation of the required Hamiltonian, we propose a modulation scheme to generate the matched effective Floquet Hamiltonian. Furthermore, we numerically simulate the multinode chiral dynamics with realistic parameters in superconducting circuits, and the results clearly show multinode chiral state transfer. Our work provides a universal and fundamental framework for understanding chiral dynamics in multinode networks. These findings will stimulate quantum state transfer, quantum routing, and nonreciprocal circulators in multinode networks.
Quantum networks with the ability to coherently transfer quantum states between different nodes open up possibilities for upscaling quantum technologies. In this work, we propose a theoretical protocol to implement the multinode state transfer and nonlocal state preparation in a one-dimensional network consisting of many quantum nodes coupled to a common unidirectional channel. By time-dependently modulating the coupling strength between the nodes and the channel, a quantum state stored in one node can be distributed to the other nodes through the channel, while a series of dark-state conditions ensure a desired final state. This protocol can also be used to prepare nonlocal entanglement states of these nodes, such as the W -type state. Importantly, it can be realized in various quantum platforms with currently available technologies.
Abstract In superconducting quantum circuits (SQCs), chiral routing quantum information is often realized with the ferrite circulators, which are usually bulky, lossy and require strong magnetic fields. To overcome those problems, we propose a novel method to realize chiral quantum networks by exploiting giant atom effects in SQC platforms. By assuming each coupling point being modulated with time, the interaction becomes momentum-dependent, and giant atoms will chirally emit photons due to interference effects. The chiral factor can approach 1, and both the emission direction and rate can be freely tuned by the modulating signals. We demonstrate that a high-fidelity state transfer between remote giant atoms can be realized. Our proposal can be integrated on the superconducting chip easily, and has the potential to work as a tunable toolbox for quantum information processing in future chiral quantum networks.
Perfect transfer of {\em unknown} states across distinct nodes is a basic function in bosonic quantum networks. Here we develop a general theory to construct an NNN-node bosonic network governed by the time-dependent Hamiltonian, as the universal quantum control theory for continuous-variable systems. In particular, we can activate nonadiabatic passages superposed of initial and target modes by the commutation condition about the Hamiltonian's coefficient matrix and projection operator in the representation of time-independent ancillary modes, which serves as the necessary and sufficient condition to solve the time-dependent Schrödinger equation of the full Hamiltonian. To exemplify the versatility of our theory on the Heisenberg-picture passages, we perform arbitrary state exchange between two nodes, chiral entanglement transfer among three bosonic nodes, and chiral Fock-state transfer among three of four bosonic nodes. Our work provides a promising avenue toward the universal control of any pair of nodes or modes as well as the entire bosonic network.
Perfect chiral circulation-the sequential transfer of a quantum state around a closed loop with unit fidelity-has been achieved in specific few-site systems, yet the universal physical conditions underlying this phenomenon remain unclear. We prove that discrete translational invariance and an equidistant energy spectrum together constitute the necessary and sufficient conditions for perfect chiral circulation. With this criterion established, an exact closed-form Hamiltonian valid for arbitrary NNN-site rings naturally follows. In the minimal three-site ring, we demonstrate two physically distinct realizations: Floquet engineering of a driven open chain that restores translational invariance by equalizing the couplings, and correlated doublon dynamics in an anyon-Hubbard model where fractional statistics intrinsically provide the chiral flux that renders the spectrum equidistant. Our results establish unified physical criteria for perfect chiral circulation and demonstrate their applicability across diverse platforms such as superconducting circuits, cold atoms, classical electrical circuits, and photonic synthetic dimensions.
Motivated by the need for quantum computers to communicate between multiple, well separated qubits, we introduce the task of quantum routing for distributing quantum states, and generating entanglement, between these sites. We describe regular families of coupled quantum networks which perfectly route qubits between arbitrary pairs of nodes with a high transmission rate. The ability to route multiple states simultaneously and the regularity of the networks vastly improve the utility of this scheme in comparison to the task of state transfer, leading us to propose an implementation in optical lattices.
As the field of superconducting quantum computing advances, networking qubits within a single system becomes essential for building modular processors. Modularity allows the system to circumvent scalability constraints and enable architectures and computational schemes that exploit non-local connectivity to enhance processing capabilities. This work proposes non-local entanglement generation methods based on the theory of chiral quantum waveguide dynamics, which is the quantum-optical framework that describes systems of atoms coupled non-reciprocally to a continuum of modes. We leverage these effects to design a chiral communication module composed of multiple superconducting qubits, capable of both directional single photon routing and the realization of chiral, driven-dissipative entanglement protocols.