By Yuval Boger

Last year, a group of scientists published a paper in Nature that discussed qubit shuttling, or as it was called in the paper “coherent transport of entangled atom arrays”. The work of this Harvard-led group that included scientists from QuEra Computing, MIT, and the University of Innsbruck, could prove pivotal for the development of large-scale quantum computing using neutral atom arrays.

The video below demonstrates this shuttling. This is a real video (with added red ellipses for emphasis), not an animation.

Credit: Lukin group, Harvard University

It shows groups of physical qubits that are moved at the same time. The red circles show the potential for entanglement with nearby qubits at every step.

Coherent qubit shuttling – the ability to move qubits around while preserving their quantum state – could profoundly impact how next-generation quantum computers might be built. That potential impact can be appreciated in three areas: error correction, multi-zone architecture and scale-up.

Error correction

A primary challenge in building large-scale quantum computers lies in error management. Unlike classical computing, where information from a single binary digit can be duplicated for error correction, quantum mechanics doesn’t allow for such copying (the no-cloning theorem). Therefore, quantum error correction involves spreading information across multiple qubits through entanglement to create redundancy.

The ability to move qubits while preserving their state allows entangling nearby qubits but then spreading these entangled qubits over a larger area. One such error correction code that involves spreading qubits over an area is the toric code, where logical qubits are encoded in such a way that they span a two-dimensional lattice. Because the logical qubits are spread out over a large area, localized errors affect only a small portion of the logical qubit, which makes it possible to correct the error without damaging the overall quantum information. See this article in Nature from Harvard, University of Innsbruck, MIT and AWS, for illustrations of this toric code.

1: The two logical qubits are separate
Step 2: The logical qubits are brought together
Step 3: A quantum operation is performed

Multi-zone operation

Once qubits can be moved around while preserving their state, one could envision the development of a quantum computing architecture that includes multiple zones. For instance, one could imagine an architecture with three zones:

  • A processing zone where quantum operations are performed on logical qubits.
  • A memory zone where qubits are put in a more stable state with longer coherence times.
  • A measurement zone where certain qubits can be measured mid-circuit for the purpose of error correction and conditional execution.

Enabled by qubit shuttling, qubits can be moved in and out of these zones as required.


Beyond the fact that error-corrected qubits allow meaningful execution of longer circuits, there is the question of control signals. Control signals are required to alter the state of individual qubits as well as to perform multi-qubit operations. However, as one thinks about million-qubit machines, do we expect to have millions of control signals? Imagine opening up your 4K television and discovering that every pixel has a wire going to it. That would be ridiculous. Similarly, qubit shuttling allows increasing the number of qubits without a matching increase in control signals

Additionally, qubit shuttling essentially enables any-to-any qubit connectivity. This is in contrast to fixed-layout configurations where qubits are connected to just their nearest neighbors. Any-to-any connectivity allows compressing the circuit because information can propagate with fewer information.


In conclusion, the ability to shuttle qubits around while maintaining their quantum state can have far-reaching implications for the future of quantum computing and bring us one step closer to realizing its full potential. This advancement opens up innovative approaches to error correction, multi-zone architecture, and scaling. It allows for a much more flexible, robust, and efficient quantum computing architecture that can handle complex computations and larger circuits while managing errors more effectively.

Yuval Boger is the Chief Marketing Officer for QuEra, the leader in quantum computers based on neutral atoms. QuEra’s 256-qubit computer is available for public access on Amazon Braket.

May 17, 2023