Improved readout of qubit-coupled Gottesman–Kitaev–Preskill states

Jacob Hastrup*, Ulrik Lund Andersen

*Corresponding author for this work

Research output: Contribution to journalJournal articlepeer-review


The Gottesman–Kitaev–Preskill encoding of a qubit in a harmonic oscillator is a promising building block towards fault-tolerant quantum computation. Recently, this encoding was experimentally demonstrated for the first time in trapped-ion and superconducting circuit systems. However, these systems lack some of the Gaussian operations which are critical to efficiently manipulate the encoded qubits. In particular, homodyne detection, which is the go-to method for efficient readout of the encoded qubit in the vast majority of theoretical work, is not readily available, heavily limiting the readout fidelity. Here, we present an alternative read-out strategy designed for qubit-coupled systems. Our method can improve the readout fidelity with several orders of magnitude for such systems and, surprisingly, even surpass the fidelity of homodyne detection in the low squeezing regime.

Original languageEnglish
Article number035016
JournalQuantum Science and Technology
Issue number3
Number of pages9
Publication statusPublished - 2021


  • Bosonic codes
  • Gottesman–Kitaev–Preskill states
  • Quantum error correction
  • Superconducting qubits
  • Trapped ions


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