This research addresses a fundamental challenge in quantum computing: creating scalable entangled states in quantum systems while managing noise and decoherence. While quantum information processing offers significant advantages over classical computing through properties like superposition and entanglement, implementing large-scale entanglement remains difficult with current Noisy Intermediate Scale Quantum (NISQ) devices.
The study proposes ultracold atoms in optical lattices as a promising platform to overcome these limitations. This approach leverages the system’s inherent advantages in initialization and parallel manipulation capabilities. The technique builds upon established methods of transitioning ultracold atoms from superfluid to Mott insulator states by adjusting lattice depth, allowing for precise qubit initialization under unit filling conditions.
The research advances previous work on entangled states in optical lattices by utilizing superlattices – structures created by overlapping two different optical lattices to form double wells. These superlattices enable various atomic dynamics, including superexchange coupling and controlled exchange interaction, which can be used to entangle atoms within double wells. A key advantage of this approach is the ability to perform entangling operations in parallel across the entire lattice system.
The proposed scheme for generating scalable entanglement consists of two main steps. First, atom pairs within each double well are entangled using quantum gates. Second, the double wells are shifted to single sites by modifying the superlattice phase, followed by another round of entanglement operations on the newly formed atom pairs. This process creates connections between neighboring atoms, resulting in a global entangled state.
Theoretical analysis demonstrates that this method produces genuine multipartite entanglement (GME). Additionally, the resulting quantum state shows enhanced resilience to magnetic noise-induced decoherence, as it only maintains amplitude on computational basis states with zero total spin.
While the system’s periodic nature enables parallel operations, it also presents certain limitations. The small lattice spacing required for sufficient tunneling between neighboring sites makes individual atomic control challenging. Although high-resolution imaging and tight-focused optical tweezers offer potential solutions, performing multiple distinct single-qubit operations while maintaining system coherence remains difficult within realistic timeframes. Consequently, the approach focuses on homogeneous operations and measurements across all atoms.
This work builds upon significant progress in various quantum computing platforms, including ion traps, photonic systems, Rydberg atoms, and superconducting circuits. The research acknowledges the achievements in increasing qubit numbers across these platforms while addressing the persistent challenge of generating large-scale entanglement in NISQ devices.
The proposed method represents a practical pathway toward scalable quantum computation, leveraging the unique properties of optical superlattices while working within their constraints. It demonstrates how careful system design can overcome typical limitations in quantum computing implementations, potentially advancing the field toward practical quantum information processors.
The research combines theoretical insights with practical considerations for experimental implementation, addressing both the fundamental physics of quantum entanglement and the engineering challenges of building scalable quantum systems. This balanced approach suggests a viable route toward larger-scale quantum computation while managing the inherent challenges of noise and decoherence in quantum systems.
npj Quantum Information, Published online: 29 August 2022; doi:10.1038/s41534-022-00609-0
