Amirhossein Khalajhedayati

Fast, High-Fidelity Erasure Detection of Dual-Rail Qubits with Symmetrically Coupled Readout

  1. Jimmy Shih-Chun Hung,
  2. Arbel Haim,
  3. Mouktik Raha,
  4. Gihwan Kim,
  5. Ziwen Huang,
  6. Ming-Han Chou,
  7. Mitch D'Ewart,
  8. Erik Davis,
  9. Anurag Mishra,
  10. Patricio Arrangoiz-Arriola,
  11. Amirhossein Khalajhedayati,
  12. David Hover,
  13. Fernando G.S.L. Brandão,
  14. Aashish A. Clerk,
  15. Alex Retzker,
  16. Harry Levine,
  17. and Oskar Painter
Erasure qubits are a promising platform for implementing hardware-efficient quantum error correction. Realizing the error-correction advantages of this encoding requires frequent mid-circuiterasure checks that are fast, high-fidelity, and scalable. Here, we realize erasure detection with a hardware-efficient circuit consisting of a single readout resonator dispersively and symmetrically coupled to both transmons of a dual-rail qubit. We use this circuit to demonstrate single-shot erasure detection in 384 ns with minimal impact on the dual-rail logical manifold, achieving a residual error per check of 6.0(2)×10−4, with only 8(3)×10−5 induced dephasing per check, and an erasure error per check of 2.54(1)×10−2. The high degree of matched dispersive readout coupling (χ-matching) within the dual-rail qubit code space also allows us to realize a new modality: time-continuous erasure detection performed in parallel with single-qubit gates. Here we achieve a median 7.2×10−5 error per gate with <1×10−5 error induced by erasure detection. This demonstrates a reduction in erasure detection overhead as well as a crucial ingredient for soft information quantum error correction. Together, these results establish symmetrically coupled dispersive readout as a fast, hardware-efficient, and scalable component for erasure-based quantum error correction using transmon dual-rail qubits.[/expand]
arxiv pdf

Demonstrating a long-coherence dual-rail erasure qubit using tunable transmons

  1. Harry Levine,
  2. Arbel Haim,
  3. Jimmy S.C. Hung,
  4. Nasser Alidoust,
  5. Mahmoud Kalaee,
  6. Laura DeLorenzo,
  7. E. Alex Wollack,
  8. Patricio Arrangoiz-Arriola,
  9. Amirhossein Khalajhedayati,
  10. Yotam Vaknin,
  11. Aleksander Kubica,
  12. Aashish A. Clerk,
  13. David Hover,
  14. Fernando Brandão,
  15. Alex Retzker,
  16. and Oskar Painter
Quantum error correction with erasure qubits promises significant advantages over standard error correction due to favorable thresholds for erasure errors. To realize this advantagein practice requires a qubit for which nearly all errors are such erasure errors, and the ability to check for erasure errors without dephasing the qubit. We experimentally demonstrate that a „dual-rail qubit“ consisting of a pair of resonantly-coupled transmons can form a highly coherent erasure qubit, where the erasure error rate is given by the transmon T1 but for which residual dephasing is strongly suppressed, leading to millisecond-scale coherence within the qubit subspace. We show that single-qubit gates are limited primarily by erasure errors, with erasure probability perasure=2.19(2)×10−3 per gate while the residual errors are ∼40 times lower. We further demonstrate mid-circuit detection of erasure errors while introducing <0.1% dephasing error per check. Finally, we show that the suppression of transmon noise allows this dual-rail qubit to preserve high coherence over a broad tunable operating range, offering an improved capacity to avoid frequency collisions. This work establishes transmon-based dual-rail qubits as an attractive building block for hardware-efficient quantum error correction.[/expand]
arxiv pdf