Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:2110.06954 · PRX Quantum

Characterizing Quantum Instruments: From Nondemolition Measurements to Quantum Error Correction

Roman Stricker, Davide Vodola, Alexander Erhard, Lukas Postler, M. Meth, Martin Ringbauer, Philipp Schindler, R. Blatt, Markus Müller, Thomas Monz

Published Aug 3, 2022• 7 citations
arXivHTMLPDF

Abstract

A complete toolbox for the tomographic characterization of generic instruments is experimentally applied to detect qubit loss and leakage, offering in-depth information about the failure modes that degrade quantum error correction.
DOI
10.1103/prxquantum.3.030318

Related papers

Self-consistent quantum tomography for characterizing super-accurate quantum operations

Takanori Sugiyama, Shinpei Imori, Fuyuhiko Tanaka

Bulletin of the American Physical Society•Mar 7, 2018•0 citations

Quantum error correction of a qubit loss in an addressable atomic system

Jiří Vala, K. Birgitta Whaley, David S. Weiss

We present a scheme for correcting qubit loss error while quantum computing with neutral atoms in an addressable optical lattice. The qubit loss is first detected using a quantum nondemolition measurement and then transformed into a standard qubit error by inserting a new atom in the vacated lattice site. The logical qubit, encoded here into four physical qubits with the Grassl-Beth-Pellizzari code, is reconstructed via a sequence of one projective measurement, two single-qubit gates, and three controlled-NOT operations. No ancillary qubits are required. Both quantum nondemolition and projective measurements are implemented using a cavity quantum electrodynamics system which can also detect a general leakage error and thus allow qubit loss to be corrected within the same framework. The scheme can also be applied in quantum computation with trapped ions or with photons.

arXiv:quant-ph/0510021•Physical Review A•Nov 18, 2005•41 citations

Taming Rydberg Decay with Measurement-Based Quantum Computation

Chengcheng Yu, Zi‐Han Chen, Yuhao Deng +3 more

Programmable neutral atom arrays show great promise for fault-tolerant quantum computing. A dominant physical error on this platform is qubit leakage and loss, notably decay errors from the Rydberg state during two-qubit gates. Such leakage events are particularly detrimental as they propagate, generating correlated errors that severely degrade the effective error distance of quantum error correction codes. Here, we present a novel approach to address Rydberg decay errors leveraging measurement-based quantum computation. Our scheme strategically exploits the inherent geometric structure of topological cluster states and only uses final leakage detection information to locate propagated errors originating from Rydberg decay. This eliminates the need for complex and atom-species-specific midcircuit leakage detection, offering broader applicability, e.g., to the well-established Rb atom platform. We demonstrate a high error threshold of 3.65% per cz gate for pure Rydberg decay and achieve a favorable error distance d_{e}≈d. Our method compares favorably with state-of-the-art erasure conversion protocols in the subthreshold performance, offering comparable or marginally larger logical error rates while significantly reducing experimental overhead.

arXiv:2411.04664•Physical Review Letters•Mar 23, 2026•3 citations

Gate-set tomography: calibration-free full characterization of quantum devices using error-amplifying circuits.

Robin Blume-Kohout

•Sep 1, 2014•0 citations

Currently Realizable Quantum Error Detection/Correction Algorithms for Superconducting Qubits

Kyle Keane, Alexander N. Korotkov

Bulletin of the American Physical Society•Mar 21, 2011•1 citation

Characterizing mid-circuit measurements on a superconducting qubit using gate set tomography

Kenneth Rudinger, Guilhem J. Ribeill, Luke C. G. Govia +6 more

Measurements that occur within the internal layers of a quantum circuit -- mid-circuit measurements -- are an important quantum computing primitive, most notably for quantum error correction. Mid-circuit measurements have both classical and quantum outputs, so they can be subject to error modes that do not exist for measurements that terminate quantum circuits. Here we show how to characterize mid-circuit measurements, modelled by quantum instruments, using a technique that we call quantum instrument linear gate set tomography (QILGST). We then apply this technique to characterize a dispersive measurement on a superconducting transmon qubit within a multiqubit system. By varying the delay time between the measurement pulse and subsequent gates, we explore the impact of residual cavity photon population on measurement error. QILGST can resolve different error modes and quantify the total error from a measurement; in our experiment, for delay times above 1000 ns we measured a total error rate (i.e., half diamond distance) of $ε_{\diamond} = 8.1 \pm 1.4 \%$, a readout fidelity of $97.0 \pm 0.3\%$, and output quantum state fidelities of $96.7 \pm 0.6\%$ and $93.7 \pm 0.7\%$ when measuring $0$ and $1$, respectively.

arXiv:2103.03008•Mar 4, 2021•1 citation
We present a scheme for correcting qubit loss error while quantum computing with neutral atoms in an addressable optical lattice. The qubit loss is first detected using a quantum nondemolition measurement and then transformed into a standard qubit error by inserting a new atom in the vacated lattice site. The logical qubit, encoded here into four physical qubits with the Grassl-Beth-Pellizzari code, is reconstructed via a sequence of one projective measurement, two single-qubit gates, and three controlled-NOT operations. No ancillary qubits are required. Both quantum nondemolition and projective measurements are implemented using a cavity quantum electrodynamics system which can also detect a general leakage error and thus allow qubit loss to be corrected within the same framework. The scheme can also be applied in quantum computation with trapped ions or with photons.
Programmable neutral atom arrays show great promise for fault-tolerant quantum computing. A dominant physical error on this platform is qubit leakage and loss, notably decay errors from the Rydberg state during two-qubit gates. Such leakage events are particularly detrimental as they propagate, generating correlated errors that severely degrade the effective error distance of quantum error correction codes. Here, we present a novel approach to address Rydberg decay errors leveraging measurement-based quantum computation. Our scheme strategically exploits the inherent geometric structure of topological cluster states and only uses final leakage detection information to locate propagated errors originating from Rydberg decay. This eliminates the need for complex and atom-species-specific midcircuit leakage detection, offering broader applicability, e.g., to the well-established Rb atom platform. We demonstrate a high error threshold of 3.65% per cz gate for pure Rydberg decay and achieve a favorable error distance d_{e}≈d. Our method compares favorably with state-of-the-art erasure conversion protocols in the subthreshold performance, offering comparable or marginally larger logical error rates while significantly reducing experimental overhead.
Measurements that occur within the internal layers of a quantum circuit -- mid-circuit measurements -- are an important quantum computing primitive, most notably for quantum error correction. Mid-circuit measurements have both classical and quantum outputs, so they can be subject to error modes that do not exist for measurements that terminate quantum circuits. Here we show how to characterize mid-circuit measurements, modelled by quantum instruments, using a technique that we call quantum instrument linear gate set tomography (QILGST). We then apply this technique to characterize a dispersive measurement on a superconducting transmon qubit within a multiqubit system. By varying the delay time between the measurement pulse and subsequent gates, we explore the impact of residual cavity photon population on measurement error. QILGST can resolve different error modes and quantify the total error from a measurement; in our experiment, for delay times above 1000 ns we measured a total error rate (i.e., half diamond distance) of ε⋄=8.1±1.4%ε_{\diamond} = 8.1 \pm 1.4 \%ε⋄​=8.1±1.4%, a readout fidelity of 97.0±0.3%97.0 \pm 0.3\%97.0±0.3%, and output quantum state fidelities of 96.7±0.6%96.7 \pm 0.6\%96.7±0.6% and 93.7±0.7%93.7 \pm 0.7\%93.7±0.7% when measuring 000 and 111, respectively.