Atoms Linked Remotely with New Technique, Speeding Entanglement by 90 Percent

Scientists at the The Chinese University of Hong Kong in collaboration with Rutgers University and University of Edinburgh, led by Lingyi Kong, have presented a new method for creating entanglement between qubits in neutral atom arrays that addresses limitations inherent in current technology. They demonstrate a directional-transport (DT)-based remote CZ gate and compiler that significantly improves upon existing approaches utilising acousto-optic deflectors (AODs). The system strategically reserves AODs for initial channel setup and fine adjustments, relying primarily on DT to move Rydberg excitations and establish remote entanglement between stationary qubits. This hybrid remote CZ approach reduces the duration of the entangling stage by approximately 50 to 90 percent and overcomes the range restrictions of traditional AOD-based shuttling, paving the way for enhanced long-distance connectivity in quantum computing architectures.

Hybrid compilation accelerates neutral atom entanglement via Rydberg excitation

Entangling-stage duration has been reduced by approximately 50 to 90 percent using a new hybrid compilation methodology for neutral atom arrays. This substantial decrease overcomes limitations previously imposed by objective-limited shuttling, a process where qubits, the fundamental units of quantum information, are physically moved using acousto-optic deflectors (AODs). These AODs function as tiny, controllable mirrors, steering light beams to manipulate the atoms. Both the speed and range of these AOD-based systems severely restricted long-distance connectivity, making entanglement between non-adjacent qubits a significant challenge in scaling quantum processors. The difficulty arises from the physical limitations of the AODs themselves, including their switching speeds and the precision with which they can target individual atoms. Benchmarks, including Quantum Fourier Transform circuits, a crucial component in many quantum algorithms, showed output fidelity improved from 3.61×10−1 to 4.85×10−1 at smaller scales and from 1.67×10−12 to 3.70×10−7 in more demanding scenarios involving a greater number of qubits and more complex operations. Static compilation, a pre-determined sequence of operations, lowered channel duration to 2.45 × 103 at ten qubits, and 9.26 × 104 at two hundred, sharply outperforming existing compilers like ZAC and ZAP, which rely more heavily on physical atom movement. Dynamic compilation, which adjusts the operations during runtime, offered a slight increase in duration, accepting 2.36 × 105 at two hundred qubits, in exchange for enhanced fidelity, suggesting a trade-off between speed and accuracy that can be tailored to specific applications.

Hybrid Quantum Entanglement via Acousto-Optic Deflector Initialisation and Rydberg Excitation

A hybrid quantum computing approach is being developed, combining acousto-optic deflectors (AODs) with directional transport (DT) to improve entanglement speed and range. AODs initially set up channels and perform micro-tuning, physically moving atoms to precise locations, while DT propagates a quantum state via a Rydberg excitation along a pre-arranged chain of ancilla atoms. Ancilla atoms act as intermediaries, facilitating the transfer of quantum information without directly manipulating the qubits involved in the entanglement process. Propagating a Rydberg excitation, temporarily boosting an atom to a very high energy level, specifically, the Rydberg state, along a chain of specially prepared ancilla atoms facilitates this technique. This process allows the quantum state to be transferred without physically moving the qubits themselves, resembling passing a message down a line of people. The Rydberg state is chosen because of its enhanced interaction range, allowing for efficient transfer of quantum information between atoms. The energy level of the Rydberg state is carefully controlled to ensure efficient excitation and de-excitation, minimising errors during the transfer process. This method circumvents the limitations of AOD-based shuttling, which requires precise and rapid physical movement of atoms over potentially long distances.

Advancing neutral atom entanglement via directional transport and reconfigurable processors

Neutral atom arrays are rapidly becoming a leading platform for building scalable quantum computers, offering a potential path beyond the limitations of superconducting qubits and trapped ions. Neutral atoms, held in place by optical tweezers, offer long coherence times and strong interactions when excited to Rydberg states, making them ideal candidates for quantum computation. This new hybrid approach demonstrably improves entanglement speed and range, though further investigation is needed to understand its performance with increasingly complex quantum circuits. The ability to efficiently entangle qubits is crucial for performing complex quantum algorithms, and this new method represents a significant step towards building larger and more powerful quantum computers. Compilers, software translating algorithms into machine-readable instructions, are important for unlocking the full potential of these arrays, as highlighted by concurrent work from Tan and colleagues exploring reconfigurable atom array processors. Reconfigurable processors allow for dynamic adjustment of the array geometry, enabling more efficient execution of quantum algorithms. The development of both efficient compilers and reconfigurable processors is essential for realising the full potential of neutral atom quantum computing.

This directional-transport system represents a major advance in neutral atom computing by addressing performance concerns with increasingly intricate quantum circuits. Shifting entanglement from physically moving atoms using AODs to directional transport bypasses limitations in speed and range. Rydberg excitation, a temporary energy boost enabling atom movement, is utilised to create connections between qubits, the basic units of quantum information. This methodology establishes a pathway towards scalable entanglement in neutral atom arrays by intelligently combining acousto-optic deflectors with directional transport, a technique propagating quantum information via temporary energy boosts to atoms. By reserving traditional atom-steering devices for initial setup, the system primarily utilises directional transport to connect qubits, enabling remote entanglement between stationary qubits, sharply reducing interaction time and extending the range of connectivity within the quantum processor. The ability to achieve remote entanglement without physically moving the qubits is a key advantage, as it reduces the complexity and error rate of the entanglement process, ultimately contributing to the development of more robust and scalable quantum computers.

The researchers successfully demonstrated a new method for creating entanglement between qubits in neutral atom arrays using directional transport. This approach reduces the time required for entanglement by 50 to 90 percent compared to existing techniques relying solely on atom movement. By primarily utilising directional transport, rather than physically moving atoms, the system overcomes limitations in speed and range, enabling longer-distance connectivity. The team also developed a compiler to translate algorithms into instructions for these arrays, representing progress towards building larger and more powerful quantum computers.