We are exploring several different approaches towards scalable quantum computing based on neutral atom qubits with long range Rydberg blockade. Rydberg interactions can be used to entangle single atom qubits, to entangle ensemble qubits, and to establish hybrid entanglement between atomic and other qubits. Using a 2D array of atomic qubits we demonstrate high fidelity single qubit control together with entanglement of nearby qubits. The ratio of qubit coherence time to entangling gate time exceeds 1000.
We are exploring several different approaches towards scalable quantum computing based on neutral atom qubits with long range Rydberg blockade. Rydberg interactions can be used to entangle single atom qubits, to entangle ensemble qubits, and to establish hybrid entanglement between atomic and other qubits. Using a 2D array of atomic qubits we demonstrate high fidelity single qubit control together with entanglement of nearby qubits. The ratio of qubit coherence time to entangling gate time exceeds 1000.
Neutral atoms provide an excellent resource for quantum information processing, combining the long atomic coherence times of the hyperfine ground-state with strong dipole-dipole interactions of highly excited Rydberg states for generating deterministic entanglement between qubits separated by < 10 µm [1]. Scalable long-range interactions can be obtained by coupling the atomic array to a superconducting microwave cavity enabling hybrid quantum information processing where the cavity-mediated entanglement allows atoms to be coupled over cm length scales. We present the first steps towards such an experiment incorporating high fidelity readout using an sCMOS camera [2] and the ability to drive fast, optically addressable rotations of the hyperfine-encoded qubits to the Rydberg state. Using our sub-kHz cavitystabilised laser system [3] we demonstrate coherent control of single Rydberg atoms, performing Ramsey spectroscopy to determine coherence time and to generate entanglement between a pair of atoms separated by 6 µm. Combining this excitation scheme with our ground-state Raman lasers we show progress towards the implementation of a mesoscopic Rydberg gate based on electromagnetically induced transparency (EIT) offering robust entanglement of multi-atom ensembles [4].
Individual neutral atoms excited to Rydberg states are a promising platform for quantum simulation and quantum information processing. However, experimental progress to date has been limited by short coherence times and relatively low gate fidelities associated with such Rydberg excitations. We report progress towards high-fidelity quantum control of Rydberg-atom qubits. Enabled by a reduction in laser phase noise, our approach yields a significant improvement in coherence properties of individual qubits. We further show that this high-fidelity control extends to the multi-particle case by preparing a two-atom entangled state with a fidelity exceeding 0.97(3), and extending its lifetime with a two-atom dynamical decoupling protocol. These advances open up new prospects for scalable quantum simulation and quantum computation with neutral atoms.
Neutral atom quantum computing utilizes laser-trapped neutral atoms as qubits and realizes quantum logic gate operations through Rydberg-state interactions. In recent years, it has become one of the most vibrant directions in quantum computing hardware. This paper systematically reviews the working principles of neutral-atom quantum computers, including qubit encoding, atom trapping and manipulation, Rydberg states and interactions, the Rydberg blockade quantum gate mechanism, and atom rearrangement with reconfigurable architectures. The mainstream technical routes are surveyed, represented by optical tweezer arrays combined with Rydberg interactions, optical lattice schemes, and dipole trap arrays. A panoramic review is provided of domestic and international research progress from theoretical foundations in 2000 to the latest achievements in 2026, including thousand-qubit-scale systems, logical qubits, and quantum error correction experiments. Key breakthroughs are highlighted, such as the 6100-atom qubit array, continuous operation of a 3000-qubit system, quantum simulation of the Kitaev honeycomb model, toric code error correction demonstrations, encoding rates exceeding 1/2, and fault-tolerant architectures. The core bottlenecks are analyzed in depth, including the scalability--fidelity trade-off, engineering implementation of quantum error correction, atom loss and mid-circuit replenishment, laser system industrialization, control electronics scalability, and long-distance quantum interconnection. This paper aims to provide a systematic reference for academic research and technological development in this field.
Abstract The ability to perform entangling quantum operations with low error rates in a scalable fashion is a central element of useful quantum information processing 1 . Neutral-atom arrays have recently emerged as a promising quantum computing platform, featuring coherent control over hundreds of qubits 2,3 and any-to-any gate connectivity in a flexible, dynamically reconfigurable architecture 4 . The main outstanding challenge has been to reduce errors in entangling operations mediated through Rydberg interactions 5 . Here we report the realization of two-qubit entangling gates with 99.5% fidelity on up to 60 atoms in parallel, surpassing the surface-code threshold for error correction 6,7 . Our method uses fast, single-pulse gates based on optimal control 8 , atomic dark states to reduce scattering 9 and improvements to Rydberg excitation and atom cooling. We benchmark fidelity using several methods based on repeated gate applications 10,11 , characterize the physical error sources and outline future improvements. Finally, we generalize our method to design entangling gates involving a higher number of qubits, which we demonstrate by realizing low-error three-qubit gates 12,13 . By enabling high-fidelity operation in a scalable, highly connected system, these advances lay the groundwork for large-scale implementation of quantum algorithms 14 , error-corrected circuits 7 and digital simulations 15 .
We present experimental results on two-qubit Rydberg-blockade quantum gates and entanglement in a two-dimensional qubit array. Without postselection against atom loss we achieve a Bell state fidelity of $0.73\ifmmode\pm\else\textpm\fi{}0.05$. The experiments are performed in an array of single Cs atom qubits with a site to site spacing of $3.8\phantom{\rule{0.28em}{0ex}}\ensuremath{\mu}\mathrm{m}$. Using the standard protocol for a Rydberg-blockade CZ gate together with single qubit operations we create Bell states and measure their fidelity using parity oscillations. We analyze the role of ac Stark shifts that occur when using two-photon Rydberg excitation and show how to tune experimental conditions for optimal gate fidelity.
This thesis reports progress towards using hyperfine-encoded neutral atomic ensembles for quantum information applications. Ensemble qubits are alternative building blocks to process quantum information, while circumventing the challenges preparing a low-entropy single-atom qubit register. While ensemble approach inherits the single-atom quantum gate protocols, cooperative atom-light interaction makes it favorable platform to implement atom-photon interface, such as quantum memory. We have demonstrated semi-deterministic preparation of W-state, which we use as an ensemble qubit. Observed 50–60% preparation fidelity shows discrepancy to expected > 80% fidelity including known imperfections. We suspect Ground-Rydberg and Rydberg-Rydberg molecular interactions within the ensemble modify the dynamics. State tomography and Ramsey experiment clearly identified that majority of constituents in an ensemble are indeed entangled. We report the first measurement of W-state coherence time as 2.6ms for 7.6 atoms, which is long enough to perform 2600 Rydberg-mediated quantum gate operations. The first demonstration of Rydberg blockade between two ensembles happened in the same apparatus. We observe blockade fidelity of 0.89 (uncorrected) and near unity when post-selected on successful N = 1 Fock state preparation of Control ensemble. For weakly blockaded cases, Target ensemble remained as a perturber inhibiting Control ensemble from de-excitation. We discuss the efficacy of optical lattice insertion to suppress molecular interactions that might have been affecting the Rydberg dynamics. High fidelity, parallel, low loss fluorescence detection of hyperfine ground state of rubidium atoms is presented. Enforced cycling transition scattering minimally alters the internal states. We achieve mean state detection fidelity of 97% (uncorrected) and 98.7% (SPAM error corrected), with atom loss rate < 2% and hyperfine-changing rate < 2%. This scalable technique is also compatible with ensemble qubits and error correcting schemes. Technical developments on apparatus, lasers, supporting hardware and software are discussed. Automatic beam alignment system is implemented to correct long term drift of tightly focused addressing beams. Achieved pointing stability of 60 nm. Two home-made, high performing, cavity-enhanced frequency doubling systems were constructed to meet experimental demand. We observe 960/480 system output as high as 180 mW with 600 mW fundamental, and 1540/770 system output as high as 13.97 W from 19 W fundamental.