A Logic Architecture That Combines Motion and In-Place Entangling ✛ ✎
Context
This work stands apart from its neighbors in quantum computing: nearby studies cover entanglement, quantum error correction, and logical qubits, but this architecture, with its motion and in-place entangling, stands out. Most logical-qubit experiments use an entanglement zone, where atoms are moved before every two-qubit operation. That simplifies calibration but raises doubts about meeting the threshold theorem for large-scale fault tolerance. Here, movement is used sparingly: only for initialization and permutation, while entangling is done in place via individual optical addressing.
Methods
The experiments were performed on a 42-qubit section of the Sqale processor with a 14×16 optical tweezer array and a 6 μm pitch. Atoms move in parallel along trajectories with minimal jerk over 7 ms, with one spin-echo pulse. Logical qubits are encoded using the [[4,2,2]] code (single-error detection) and its concatenation into [[16,4,4]] (single-error correction). Circuits are compiled into a native gate set: CZ, global rotations, Rz, movement, and measurement. Post-processing includes postselection on atom loss, loss correction, decoding, and leakage detection using dedicated flag qubits.
Results
In Shor's algorithm (precompiled, not scalable), the logical versions reduced the total variation distance by up to 2 times compared with the physical version. For constant-depth CX ladders on 8 and 12 logical qubits, the error dropped by a factor of 2–4, despite the sequential execution of entangling operations on current hardware. Preparing the [[16,4,4]] code state gave an 8-fold improvement: an average error of 0.0151 versus 0.1312 for the unencoded version. Postselecting on atom loss and flags substantially reduces yield, but loss correction increases it at the cost of a slight rise in error.
Implications
Unlike neighboring works, where movement to an entanglement zone occurs before every gate, here movement is used only for initialization and occasional permutations, while entangling is done in place. This reduces error accumulation and runtime, which is critical for the threshold theorem. The architecture supports constant-depth circuits, which are advantageous for neutral atoms with slow gates but many qubits. The results show that combining movement with local addressing can be more efficient than a zone-based approach.
Future development
Fully realizing the constant-depth architecture will require parallel gates and mid-circuit measurements, which have already been demonstrated in other neutral-atom systems. Dual-species arrays or hidden beams would allow in-place readout without movement. Scaling to tens and hundreds of thousands of qubits is achievable, as recent arrays with 6100 qubits have shown. Further improvements in gate fidelity, SPAM, and continuous atom reloading will be key.
Impact
The results will influence the development of fault-tolerant quantum computers based on neutral atoms, especially for materials science problems such as the Anderson impurity model, where constant-depth CX ladders and the Hadamard test are critical.
Next steps
Implement parallel gates and mid-circuit measurements on Sqale; explore decoding that accounts for physical circuits to correct losses; scale to the [[16,4,4]] code with repeated syndrome rounds.
Key open problems
This connects to open problems in quantum error correction: achieving the threshold theorem under realistic noise and atom movement; developing scalable decoders for constant-depth circuits with many logical qubits; and reducing the overhead of movement without losing connectivity.
The knowledge machine's view
This section is addressed to the author of the paper and their colleagues. Neighbouring works were found by meaning-based search across our archive, not by word overlap. We do not review: we show the field around the work.
What the work does
On Infleqtion's 114-qubit Sqale processor, the team implemented an architecture that combines atom movement with optical addressing for in-place entanglement. In experiments with logical qubits (Shor's algorithm, CX ladders, the [[16,4,4]] code), they achieved up to an 8-fold improvement in logical performance over physical performance. The authors use movement sparingly, only for initialization and permutation, while entanglement is performed in place.
Where its strength is
The strength of the work lies in demonstrating that in-place entanglement with individual addressing reduces overhead compared to an entanglement zone, and in experimentally confirming the improvement in logical performance on a real processor.
Where it could go next
- It might be interesting to compare this approach with error-squeezing codes from the quantum bicycle work: perhaps combining them could enhance fault tolerance.based on: Bicycle Architecture: A Quantum Computer from Modules arXiv:2506.03094v1
- A related idea is quantum iceberg codes, where errors make the computer smarter; it may be worth exploring how adaptive schemes could use error information in your architecture.based on: Iceberg Quantum Codes: How Errors Make Computers Smarter arXiv:2602.22211
- There is also work on quantum networks with optical switches: your atom-movement architecture might be extended to inter-node links.based on: Quantum Networks: How Optical Switches Link Processors arXiv:2501.05598
Worth trying
- Test the preparation of other high-distance codes, such as [[7,1,3]], on the current architecture.
- Investigate how postselection on atom loss affects algorithm speed and compare it with the zone-based approach.
- Explore the possibility of parallel entanglement operations using individual addressing to speed up circuits.
Why this may matter
This work charts a path toward scalable fault-tolerant quantum computing by showing that combining movement with in-place entanglement can be more efficient than the zone-based approach, which is important for practical quantum computers.
Nearby works in our archive
- A Quantum Cat on Guard for Computingsimilarity 0.53
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- Bicycle Architecture: A Quantum Computer from Modulessimilarity 0.51
- Quantum Networks: How Optical Switches Link Processorssimilarity 0.51
- Iceberg Quantum Codes: How Errors Make Computers Smartersimilarity 0.50
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The archive is sparse around this work: the closest review is only 0.53, against a usual 0.64. It looks like few have drilled nearby.
Moving an atom takes 7 milliseconds, and its temperature after the move rises from 5.1 to 9.1 microkelvin—still colder than the cosmic microwave background.
The idea of moving qubits to perform operations echoes the quantum computers in Greg Egan's novel 'Permutation City', where information is physically rearranged in space.
Key numbers
- TVD improvement in Shor's algorithm: up to 2 times
- error reduction in CX ladders: 2–4 times
- improvement in the [[16,4,4]] code: 8 times
- average error of encoded preparation: 0.0151
- average error of unencoded preparation: 0.1312