Quantum State Circulation Achieved in Photon Lattice with Robustness for Any Number of Photons

The controlled movement of quantum information represents a fundamental challenge in building powerful quantum technologies, and recent work by Souvik Bandyopadhyay, Anushya Chandran, and Philip JD Crowley from Boston University details a significant step towards achieving this goal. The researchers demonstrate a method for creating a continuous, unidirectional flow of quantum states between interconnected components, a phenomenon known as chiral state circulation. This circulation, achieved through a carefully designed system of light-trapping cavities coupled to a quantum bit, offers a robust way to prepare and isolate quantum information, and crucially, the team shows that this flow persists for increasingly long durations as more photons are involved. This advance paves the way for building more resilient and efficient quantum devices capable of manipulating information with unprecedented precision.

Quantum state transfer between subsystems is essential for the operation of a quantum computer, particularly for state preparation and isolation. Researchers have developed a cavity-QED architecture, comprising three cavities coupled to a qubit, designed to facilitate the circulation of any photonic state. This circulation originates from topologically protected chiral boundary states within the associated photon lattice, rendering it robust to perturbation. Calculations demonstrate that the circulation persists for timescales that increase with the total photon number.

Unidirectional Photonic Routing with Single Qubit

This work details the creation of a non-reciprocal photonic router using a three-cavity system coupled to a single qubit. The device functions as a unidirectional router, directing photons from one cavity to another depending on the coupling strength, mimicking a transmission line with strong coupling to the output cavities. Simulations demonstrate successful routing of photons and a corresponding imbalance in detector signals, confirming the unidirectional circulation of photons and predictable evolution of cavity populations and qubit state.

Robust Quantum State Circulation via Chiral Boundaries

Scientists have demonstrated a novel method for circulating quantum states between interconnected systems. This work centers on a cavity-QED architecture, comprising three cavities linked to a single qubit, where any photonic state reliably circulates between the cavities in a predictable sequence. Experiments reveal that a state initially introduced into the first cavity will predictably move to the second, then the third, and ultimately return to the first, completing a continuous cycle. The team measured the characteristics of this circulation, finding it originates from protected chiral boundary states within a photon lattice, making the process remarkably robust to external disturbances.

Analysis of the system demonstrates that the circulation period scales with the total photon number. Specifically, the team showed that the circulation lifetime increases as the photon number increases, indicating a highly stable and persistent quantum pathway. Further experiments involved a Floquet protocol, which successfully generated the desired conditions for sustained circulation. Measurements confirm the existence of topologically protected chiral boundary modes, localized near specific points on the photon lattice, which are crucial for maintaining the unidirectional flow of quantum information. The team calculated the position of these boundary modes, demonstrating their alignment with the predicted theoretical locations and confirming the robustness of the circulation process.

Unidirectional Quantum State Circulation Demonstrated

Researchers have demonstrated a novel architecture for controlling the circulation of quantum states within a system of coupled cavities and a qubit. This work establishes a method for transferring any photonic state between cavities in a unidirectional and repeating manner, effectively creating a closed loop for quantum information. The circulation arises from specifically engineered chiral boundary states within a photon lattice, which provides inherent robustness against external disturbances. The team verified that this circulation persists for extended time scales, increasing with the number of photons involved, and developed a protocol to precisely control the system’s Hamiltonian.

This achievement represents a significant step towards building more complex quantum systems capable of reliable state manipulation and isolation. By demonstrating a protected and persistent circulation of quantum states, the researchers have laid the groundwork for advanced quantum information processing and potentially new approaches to quantum computation. Future research directions include exploring the potential for scaling up this architecture and investigating its application in more complex quantum circuits and protocols.