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Quantum computing with neutral atoms
Loic Henriet, Lucas Beguin, Adrien Signoles, Thierry Lahaye, Antoine Browaeys, Georges-Olivier Reymond, Christophe Jurczak
TL;DR
The paper addresses how neutral-atom quantum processors can provide useful computation during the Noisy Intermediate Scale Quantum era. It reviews their hardware and interfaces, classifies computationally efficient tasks, and finds opportunities spanning digital circuits, analog Hamiltonian programs, optimization, and quantum simulation, while identifying important resource and interfacing challenges.
Problem
Near-term quantum devices need computationally useful applications that exploit available hardware before universal fault-tolerant quantum computers exist.
Method
The paper reviews neutral-atom processors from atomic qubits through application interfaces and organizes tasks across digital gate-based and analog Hamiltonian-based programming.
Results
Neutral-atom devices support a broad range of applications, including hardware-efficient variational algorithms, quantum simulation, and standard computational challenges, with MIS potentially outperforming classical algorithms at several hundred sites.
Takeaways & Limitations
Fully programmable neutral-atom processors offer a route toward quantum-accelerated computing and future fault-tolerant computing, networking, and metrology.
Takeaways & Limitations
Some quantum algorithms remain impractical on near-term devices because their qubit and gate-fidelity requirements are prohibitive.
Abstract
from arXiv · showhide
The manipulation of neutral atoms by light is at the heart of countless scientific discoveries in the field of quantum physics in the last three decades. The level of control that has been achieved at the single particle level within arrays of optical traps, while preserving the fundamental properties of quantum matter (coherence, entanglement, superposition), makes these technologies prime candidates to implement disruptive computation paradigms. In this paper, we review the main characteristics of these devices from atoms / qubits to application interfaces, and propose a classification of a wide variety of tasks that can already be addressed in a computationally efficient manner in the Noisy Intermediate Scale Quantum era we are in. We illustrate how applications ranging from optimization challenges to simulation of quantum systems can be explored either at the digital level (programming gate-based circuits) or at the analog level (programming Hamiltonian sequences). We give evidence of the intrinsic scalability of neutral atom quantum processors in the 100-1,000 qubits range and introduce prospects for universal fault tolerant quantum computing and applications beyond quantum computing.
1 Introduction
Quantum processors offer specialized computational resources through qubits, superposition, and entanglement, with neutral-atom arrays providing scalable and highly connected hardware. The paper frames applications across digital gate-based and analog Hamiltonian-based processing, emphasizing near-term simulation and computational opportunities.
- Quantum computing motivation: Quantum registers encode information in qubits and exploit superposition and entanglement to support specialized computational advantages.A register of n qubits has a complex state vector of dimension 2n.
- Digital and analog processing: Digital quantum processing applies logic gates sequentially, offering universality and cross-device compatibility despite demanding ideal hardware.The paper contrasts this approach with currently available noisy devices and near-term exploration.
- Neutral-atom processors: Neutral-atom arrays can manipulate registers with up to a few thousand qubits while providing identical constituent qubits, large connectivity, and native multi-qubit gates.Each qubit is encoded in two electronic states of an atom.
- Digital and analog processing: Analog processing directly controls the Hamiltonian governing atomic evolution, enabling fine pulse control and using the system Hamiltonian as a computational resource.The paper presents analog and digital modes as complementary ways to program quantum processors.
- Near-term opportunities: Neutral-atom processors have already simulated complex quantum systems above 100 qubits, beyond the reach of classical high-performance computers.Recent engineering progress has made commercial devices increasingly conceivable.
- Near-term opportunities: Applications include quantum simulation and standard computational problems, with potential longer-term extensions to fault-tolerant computing, networking, and metrology.The paper identifies quantum simulation as especially promising and discusses broader application areas.
2 Neutral atoms arrays
Neutral-atom QPUs combine configurable atom registers with digital and analog processing, offering fast operations, large connectivity, native multi-qubit gates, and strong scalability. Their main development boundaries are register size, cycle repetition rate, decoherence, and gate fidelity.
- Operating an atomic qubit register: Each atom serves as a qubit encoded in two electronic states, while the register is reconstructed for every computation cycle.The cycle comprises register preparation, quantum processing, and readout.
- Operating an atomic qubit register: Processing takes less than 100 µs, whereas loading and readout extend the overall computation sequence to approximately 200 ms.Preparation and readout therefore contribute substantially to the full cycle duration.
- Digital quantum processing: Rydberg-mediated two-qubit gates can run within 1 µs at a 1 MHz clock rate, with experimentally measured fidelities of F = 94.1%.Current imperfections still permit more than a hundred gates within the system’s typical coherence time.
- Digital quantum processing: Neutral-atom devices reduce connectivity overhead by 5 to 10 times versus nearest-neighbor devices and can natively implement multi-qubit gates such as Toffoli.A Toffoli gate requires seven pulses natively, compared with at least six CNOT and nine single-qubit gates on platforms without native implementation.
- Prospects for improving the QPUs performances: Scalability mainly requires increasing the number of optical tweezers rather than manufacturing new chips, while future improvements target thousands of qubits, faster repetition, lower decoherence, and higher gate fidelities.The current register size is chiefly limited by trapping-laser power and imaging capability; repetition rate is expected to improve by an order of magnitude.
- Analog quantum processing: Neutral atoms support analog simulation of broad spin Hamiltonians, including XXZ and non-spin-conserving models, with a quality factor Q ∼ 10^2.Rydberg interaction energies reach tens of MHz, at least two orders of magnitude above decoherence-associated energy scales.
3 Applications of a neutral atom QPU
Neutral atom QPUs support quantum simulation and computing on the same physical platform, using analog Hamiltonian control, digital circuits, and hybrid variational procedures. Applications span electronic and lattice-gauge systems, optimization, and machine learning, while simulation scope and near-term resources impose limitations.
- Application frameworks: Neutral atom QPUs implement both Quantum Simulation and Quantum Computing on the same physical platform.The frameworks are conceptually different but use the same hardware.
- Quantum Simulation: Analog Quantum Simulation directly realizes target spin Hamiltonians, requiring relatively little control and few operations but lacking full generality.Hybrid methods extend capabilities, while digital circuits address models that are intrinsically hard to simulate with neutral-atom resource Hamiltonians.
- Hybrid variational methods: Hybrid variational procedures combine quantum-state preparation and measurement with classical optimization, reducing coherence-time requirements and potentially accelerating selected tasks.The quantum processor estimates an objective function from repeated measurements, while the classical processor updates variational parameters.
- Quantum Simulation applications: Neutral atom simulation applications include many-body physics, electronic systems, and lattice gauge theories across condensed matter, chemistry, nuclear, and high-energy physics.Electronic Hamiltonians can be mapped onto spin Hamiltonians, although two-dimensional mappings can introduce non-local interactions.
- Quantum Computing applications: Several-hundred-site Maximum Independent Set instances could outperform the best existing classical algorithms, although quantum speedup for variational computational procedures lacks clear proof.Hardware-efficient algorithms exploit operations native to the chosen platform, including neutral-atom implementations of MIS.
4 Perspectives
Neutral-atom platforms offer routes to larger, more capable quantum processors and to applications beyond standalone quantum computing. Longer-term prospects include modular fault-tolerant architectures, photonic interfaces, quantum memories, and engineered photon interactions, although coherent processor–photon interfaces remain experimentally challenging.
- Hardware scaling: 100–1,000 qubits and beyond are identified as a hardware-development prospect for neutral-atom processors.The paper links this range to future hardware improvements and expanded computational capabilities.
- Fault-tolerant architectures: Coupling processors with optical interconnects could substantially increase available qubits and support large-scale surface-code error correction.The paper presents this multi-core architecture as one possible path toward general-purpose fault-tolerant quantum computing with neutral atoms.
- Photonic interfaces: Coherent interfaces between atomic qubits and single photons are a major experimental challenge for connecting distinct processors.Efficient interfaces with the outer world are also described as opening additional development avenues.
- Photonic interfaces: Atomic ensembles can serve as quantum memories for photonic qubits by storing incoming-photon information through electromagnetically induced transparency.Under EIT, photons propagate as slow light–matter excitations called polaritons.
- Photonic interfaces: EIT combined with strong dipole–dipole interactions in Rydberg media can engineer single-particle nonlinearities between photons.The interaction occurs between the atomic components of two polaritons inside the medium.
- Broader applications: Neutral-atom devices are presented as promising platforms for multiple key technologies in the second quantum revolution.The perspectives summarized include quantum computing, networking, metrology, and photonic applications.