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Bultink CC, O’Brien TE, Vollmer R, Muthusubramanian N, Beekman MW, Rol MA, Fu X, Tarasinski B, Ostroukh V, Varbanov B, Bruno A, DiCarlo L. Protecting quantum entanglement from leakage and qubit errors via repetitive parity measurements. Sci Adv 2020; 6:eaay3050. [PMID: 32219159 PMCID: PMC7083610 DOI: 10.1126/sciadv.aay3050] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Accepted: 12/26/2019] [Indexed: 06/10/2023]
Abstract
Protecting quantum information from errors is essential for large-scale quantum computation. Quantum error correction (QEC) encodes information in entangled states of many qubits and performs parity measurements to identify errors without destroying the encoded information. However, traditional QEC cannot handle leakage from the qubit computational space. Leakage affects leading experimental platforms, based on trapped ions and superconducting circuits, which use effective qubits within many-level physical systems. We investigate how two-transmon entangled states evolve under repeated parity measurements and demonstrate the use of hidden Markov models to detect leakage using only the record of parity measurement outcomes required for QEC. We show the stabilization of Bell states over up to 26 parity measurements by mitigating leakage using postselection and correcting qubit errors using Pauli-frame transformations. Our leakage identification method is computationally efficient and thus compatible with real-time leakage tracking and correction in larger quantum processors.
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Affiliation(s)
- C. C. Bultink
- QuTech, Delft University of Technology P.O. Box 5046, 2600 GA Delft, Netherlands
- Kavli Institute of Nanoscience, Delft University of Technology P.O. Box 5046, 2600 GA Delft, Netherlands
| | - T. E. O’Brien
- Instituut-Lorentz for Theoretical Physics, Leiden University P.O. Box 9506, 2300 RA Leiden, Netherlands
| | - R. Vollmer
- QuTech, Delft University of Technology P.O. Box 5046, 2600 GA Delft, Netherlands
- Kavli Institute of Nanoscience, Delft University of Technology P.O. Box 5046, 2600 GA Delft, Netherlands
| | - N. Muthusubramanian
- QuTech, Delft University of Technology P.O. Box 5046, 2600 GA Delft, Netherlands
- Kavli Institute of Nanoscience, Delft University of Technology P.O. Box 5046, 2600 GA Delft, Netherlands
| | - M. W. Beekman
- QuTech, Delft University of Technology P.O. Box 5046, 2600 GA Delft, Netherlands
- Kavli Institute of Nanoscience, Delft University of Technology P.O. Box 5046, 2600 GA Delft, Netherlands
- Netherlands Organisation for Applied Scientific Research (TNO), P.O. Box 155, 2600 AD Delft, Netherlands
| | - M. A. Rol
- QuTech, Delft University of Technology P.O. Box 5046, 2600 GA Delft, Netherlands
- Kavli Institute of Nanoscience, Delft University of Technology P.O. Box 5046, 2600 GA Delft, Netherlands
| | - X. Fu
- QuTech, Delft University of Technology P.O. Box 5046, 2600 GA Delft, Netherlands
| | - B. Tarasinski
- QuTech, Delft University of Technology P.O. Box 5046, 2600 GA Delft, Netherlands
- Kavli Institute of Nanoscience, Delft University of Technology P.O. Box 5046, 2600 GA Delft, Netherlands
| | - V. Ostroukh
- QuTech, Delft University of Technology P.O. Box 5046, 2600 GA Delft, Netherlands
- Kavli Institute of Nanoscience, Delft University of Technology P.O. Box 5046, 2600 GA Delft, Netherlands
| | - B. Varbanov
- QuTech, Delft University of Technology P.O. Box 5046, 2600 GA Delft, Netherlands
- Kavli Institute of Nanoscience, Delft University of Technology P.O. Box 5046, 2600 GA Delft, Netherlands
| | - A. Bruno
- QuTech, Delft University of Technology P.O. Box 5046, 2600 GA Delft, Netherlands
- Kavli Institute of Nanoscience, Delft University of Technology P.O. Box 5046, 2600 GA Delft, Netherlands
| | - L. DiCarlo
- QuTech, Delft University of Technology P.O. Box 5046, 2600 GA Delft, Netherlands
- Kavli Institute of Nanoscience, Delft University of Technology P.O. Box 5046, 2600 GA Delft, Netherlands
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