Teleportation transition of surface codes on a superconducting quantum processor

summary

The gist

The gist The authors experimentally demonstrate a teleportation protocol for a logical qubit of the surface code with imperfect entanglement resource, charting out the many-body teleportation

In short

The authors experimentally teleported a topological surface code state using 125 qubits on a superconducting processor. They mapped out a phase diagram by tuning local entangling gates and found that injecting specific coherent qubit rotations beyond the Clifford regime can boost the entanglement threshold, demonstrating how electric-magnetic duality helps protect quantum information.

Key concepts

Topological Surface Code: This is a method for quantum error correction that uses the geometry of a 2D lattice to encode information robustly. Errors are detected by measuring stabilizer operators (syndromes) on the qubits, allowing them to be corrected without needing to know the exact state of every qubit.
Quantum Teleportation: This is a process where the quantum state of one qubit is transferred to another distant qubit using entanglement. It requires an entangled resource and a joint measurement between the sender and receiver, enabling robust communication across quantum systems.
Entangling Threshold: This is the critical limit for the strength of local entangling gates that allows for faithful teleportation of logical states. Tuning this threshold reveals the phase transition where information transfer becomes stable or unstable, guiding how much noise a system can tolerate.

Terminology used across episodes

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This episode discusses

The paper

Teleportation transition of surface codes on a superconducting quantum processor · Read on arXiv

School of Physics, Zhejiang University, Hangzhou Global Scientific and Technological Innovation Center · The Hong Kong University of Science and Technology (Guangzhou) · Hefei National Laboratory

The topological surface code is a leading candidate for harnessing long-range entanglement to protect logical quantum information against errors, and teleportation of logical states is desirable for robust quantum information processing. Nevertheless, scaling up the surface code in quantum teleportation poses a formidable challenge to experiment. Here on a superconducting quantum processor with 125 qubits, we demonstrate the robust teleportation of topological rotated surface code prepared by a linear-depth unitary circuit, with code distances up to 7. We obtain the teleportation phase diagram by tuning the local entangling gates uniformly across a finite threshold. Furthermore, we show that the entangling threshold can be boosted by coherent qubit rotations that inject magic resources beyond the Clifford regime, restoring the duality symmetry of the topological phase, which serves as a guiding principle to minimize the entanglement resource. Our results shed light on simulating and leveraging topological quantum matter on quantum devices, and pave the way to the ultimate goal of distributed fault tolerant quantum computation.

DOI: 10.1038/s41567-026-03484-0

Transcript

Introduction to the show: ident: Quantum Radio. Generated commentary on the latest quantum physics and condensed matter papers.

Kai: We're looking at the paper: "Teleportation transition of surface codes on a superconducting quantum processor".

Mira: Here's the gist of the paper. The gist The authors experimentally demonstrate a teleportation protocol for a logical qubit of the surface code with imperfect entanglement resource, charting out the many-body teleportation transition across an entangling threshold by tuning local entangling gates and coherent qubit rotations.

Kai: Quantum Error Correction Context The topological surface code is a leading candidate for harnessing long-range entanglement to protect logical quantum information against errors, and teleportation of logical states is desirable for robust quantum information processing.

Mira: It leverages topological order to robustly protect quantum information against errors, where errors are detected by measuring two types of stabilizers called syndromes, and are corrected by corresponding Pauli operations.

Kai: Scaling up the surface code is challenging but necessary to achieve higher tolerance against the errors.

Paper summary: Kai: So, to recap the main points from "Teleportation transition of surface codes on a superconducting quantum processor," the paper shows they've experimentally demonstrated a teleportation protocol for a logical qubit of the surface code using an imperfect entanglement resource.

Mira: The thesis is that you can chart out this many-body teleportation transition across an entangling threshold by tuning both local entangling gates and those coherent qubit rotations.

Lev: They claim they used a one hundred twenty-five-qubit superconducting quantum processor with tunable nearest neighbour couplings to execute this, setting up Alice and Bob in d times d square lattices <ref:2602.21293#pg2>.

Kai: The setup involves preparing a surface code on Alice prior to teleportation while Bob starts in the physical product state zero · · · zero⟩, then applying a parameterized coupling operation defined by parameters theta and t <ref:2602.21293#pg2,in the physical product state |0 · · · 0>.

Mira: The key finding is that by tuning these parameters, they found a teleportation phase diagram, and they showed that the entangling threshold can be boosted by those coherent qubit rotations.

Lev: They specifically highlighted how rotating the coherent error axis to an X plus Z direction helps inject magic resources beyond the Clifford regime, which restores the duality symmetry of the topological phase.

Kai: This symmetry restoration is what guides them to minimize the entanglement resource needed for this process, showing it's a crucial concept.

Mira: It really matters because it connects the teleportation transition directly to a phase transition in quantum matter physics.

Lev: And they also compared different decoding methods like tensor network maximum likelihood decoder and minimum-weight perfect matching decoder to see which ones gave the most accurate results for error mitigation.

Kai: The ML decoder showed logical error rates of zero point zero one four(one) for Alice and zero point zero two five(three) for Bob when teleportation is below the threshold, which gives us a baseline performance metric.

Mira: And they also compared that to the MWPM decoder results, which gave them thresholds like zero point one one six(two)pi at theta equals pi over two and zero point one six four(two)pi at theta equals pi over four <ref:2602.21293#pg2>.

Lev: The overall message of this paper is that they've characterized the resilience of encoded information against tailored noise by using their physical setup to probe the resilience of the surface code structure itself.

Kai: And it sets up a path for simulating and leveraging topological quantum matter on these actual quantum devices, which is pretty exciting for our hardware work.

Conclusion: Mira: So looking at this paper, "Teleportation transition of surface codes on a superconducting quantum processor," the authors are really focusing on how the experimental setup impacts the theoretical predictions for this system.

Kai: They’re taking that phase diagram they found and showing that it's not just an academic exercise but something you can actually build and measure on hardware.

Lev: In simple terms, what this means for us is that we have a concrete way to test if the surface code structure holds up when you introduce these specific types of noise.

Kai: It provides a foundational toolkit for probing how resilient encoded information is against noise by using tailored noise settings.

Mira: And they proved that electric-magnetic duality enhances the entangling threshold, suggesting that competition between electric and magnetic excitations can actually help protect against errors.

Lev: For real hardware, this suggests we should focus on fostering this competition between those excitations to get better protection against errors.

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