Speaker
Description
One approach towards a utility scale quantum computer uses smaller processors that are linked via a quantum network. In such systems, both computation and error correction must be performed across these nodes. Here, we demonstrate quantum error detection across a distributed trapped-ion network. Logical qubits are encoded in physical qubits that are spatially separated across two ion traps, $\sim 2~\mathrm{m}$ apart. Shared entanglement is used as a non-local resource to measure stabilisers between them.
Our platform consists of two mixed-species ion trap modules that are linked photonically, each containing $^{88}\mathrm{Sr}^+$ network qubits and $^{43}\mathrm{Ca}^+$ circuit qubits. Remote entanglement between network qubits is created by generating one photon from each ion and interfering them, with coincident detection heralding entanglement, achieving fidelities exceeding 96\% at a rate of $\sim 10~\mathrm{s}^{-1}$ [1]. Combined with mixed-species entangling gates, and classical feedforward, we have performed teleported gates between remote circuit qubits [2].
Building on this, we implement non-local stabiliser measurements using our shared Bell pair as an ancilla. Specifically, we encode logical information in the $X$-basis subspace of two remote circuit qubits and measure the $XX$ stabiliser with local entangling operations and measurements on the network qubits. We characterise the performance of a single round of this stabiliser measurement across a range of dephasing error rates. By conditioning on successful detection outcomes, we observe clear error suppression and an improved stabiliser value. Repeating this over multiple rounds progressively enhances the stabiliser expectation value, a key requirement for quantum error correction. Finally, we will extend the protocol to entangled logical states by preparing the remote circuit qubits in a Bell state, and then detecting and correcting both phase- and bit-flip errors on this state.
Our demonstration of non-local stabiliser measurements across a
quantum network establishes a key building block for scalable, fault-tolerant quantum computing in modular architectures.
[1] D. Main et al., arXiv:2506.14334.
[2] D. Main et al., Nature 638, 383–388 (2025).
| Academic level | PhD student |
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