A quantum processor based on coherent transport of entangled atom arrays (2112.03923v1)

Abstract: The ability to engineer parallel, programmable operations between desired qubits within a quantum processor is central for building scalable quantum information systems. In most state-of-the-art approaches, qubits interact locally, constrained by the connectivity associated with their fixed spatial layout. Here, we demonstrate a quantum processor with dynamic, nonlocal connectivity, in which entangled qubits are coherently transported in a highly parallel manner across two spatial dimensions, in between layers of single- and two-qubit operations. Our approach makes use of neutral atom arrays trapped and transported by optical tweezers; hyperfine states are used for robust quantum information storage, and excitation into Rydberg states is used for entanglement generation. We use this architecture to realize programmable generation of entangled graph states such as cluster states and a 7-qubit Steane code state. Furthermore, we shuttle entangled ancilla arrays to realize a surface code with 19 qubits and a toric code state on a torus with 24 qubits. Finally, we use this architecture to realize a hybrid analog-digital evolution and employ it for measuring entanglement entropy in quantum simulations, experimentally observing non-monotonic entanglement dynamics associated with quantum many-body scars. Realizing a long-standing goal, these results pave the way toward scalable quantum processing and enable new applications ranging from simulation to metrology.

• The paper introduces a quantum processor using the coherent transport of entangled neutral atoms to achieve nonlocal connectivity and programmable quantum operations.
• The paper employs dynamic arrays controlled by optical tweezers and Rydberg excitation to implement versatile quantum error-correcting codes and entangled graph states.
• The paper achieves robust scaling with potential support for up to 2000 qubits, propelling advances in fault-tolerant quantum computing and quantum simulations.

Quantum Processor with Coherent Transport of Entangled Atom Arrays

The development of scalable quantum processors necessitates the ability to implement parallel and programmable quantum operations that go beyond the constraints of local qubit interactions typically associated with fixed spatial qubit layouts. This paper advances the field of quantum information systems by demonstrating a novel quantum processor framework that exploits the coherent transport of entangled qubit arrays using neutral atoms. The authors use optical tweezers to enable dynamic and nonlocal connectivity, transporting qubits across two-dimensional planes between layers of quantum operations, achieving scalability and programmability.

Methodology and Implementation

The core innovation lies in the creation of dynamically reconfigurable arrays of neutral atoms, entangled and manipulated to enable nonlocal connectivity across the platform. The use of hyperfine states of rubidium ${}^{87}\text{Rb}$ for robust information storage and dynamical trap configurations facilitates the coherent transport amidst quantum operations. Excitation to Rydberg states is employed for the generation of entanglement between the qubits. This approach allows for the construction of graph states, quantum error correction codes such as the 7-qubit Steane code, and surface and toric code implementations, highlighting its versatility in generating a variety of topological and graph states important for quantum computation and error correction.

Results and Theoretical Implications

One of the main achievements reported is the realization of various quantum error-correcting codes and entangled graph states, including a 24-qubit toric code. The protocol for atom movement shows resilience to entanglement decoherence over transport distances conceptually capable of accommodating up to 2000 qubits, showcasing the feasibility of large-scale entanglement transport under this architecture. The demonstration utilized single-qubit gates, controlled-Z (CZ) entangling operations, and coherent transport, showing an average raw stabilizer measurement yielding promising fidelity values characteristic of these states. The results imply a significant step towards realizing a practical and scalable quantum compute architecture.

On the theoretical front, the establishment of nonlocal connections provides promising grounds for exploring complex quantum simulations and fault-tolerant quantum circuits. Specifically, this setup enables hybrid analog-digital evolution, which the authors employed to paper non-monotonic entanglement entropy dynamics in quantum simulations. This realization opens new directions in investigating quantum many-body physics using novel hybrid computation methods.

Practical Implications and Future Prospects

This quantum processor with coherent transport breathes new life into potential scalable quantum computing implementations. The experimental framework paves the way for practical applications in quantum simulations, particularly where hybrid analog-digital models are beneficial, such as the extraction of entanglement entropy or quantum many-body scar dynamics. Moreover, the successful implementation of quantum error correction codes with high fidelity demonstrates a crucial stepping stone towards robust quantum error correction necessary for fault-tolerant quantum computing.

Future studies are anticipated to further reduce errors and improve fidelities by increasing Rydberg laser power and upgrading cooling techniques, allowing for deeper quantum circuits. Enhancements in local qubit operations through integrated laser control and mid-circuit readout advancements offer additional scalability. Collectively, these instrumental improvements increase the feasibility of constructing more complex nonlocal codes and leveraging entanglement transport, ultimately driving towards a universal, scalable quantum computing paradigm.

Conclusion

The work embodies a substantial advancement in the field of quantum computing by presenting dynamic, nonlocal qubit transport that substantiates the potential of neutral atoms as a robust platform for scalable quantum information systems. Through the coherent transport of entangled atom arrays, the paper lays foundational architecture and techniques conducive to advancing toward fault-tolerant and large-scale quantum processors, thereby catalyzing the burgeoning landscape of quantum technologies.