Nasser Alidoust

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

Manufacturing low dissipation superconducting quantum processors

  1. Ani Nersisyan,
  2. Stefano Poletto,
  3. Nasser Alidoust,
  4. Riccardo Manenti,
  5. Russ Renzas,
  6. Cat-Vu Bui,
  7. Kim Vu,
  8. Tyler Whyland,
  9. Yuvraj Mohan,
  10. Eyob A. Sete,
  11. Sam Stanwyck,
  12. Andrew Bestwick,
  13. and Matthew Reagor
Enabling applications for solid state quantum technology will require systematically reducing noise, particularly dissipation, in these systems. Yet, when multiple decay channels are
present in a system with similar weight, resolution to distinguish relatively small changes is necessary to infer improvements to noise levels. For superconducting qubits, uncontrolled variation of nominal performance makes obtaining such resolution challenging. Here, we approach this problem by investigating specific combinations of previously reported fabrication techniques on the quality of 242 thin film superconducting resonators and qubits. Our results quantify the influence of elementary processes on dissipation at key interfaces. We report that an end-to-end optimization of the manufacturing process that integrates multiple small improvements together can produce an average T¯¯¯¯1=76±13 μs across 24 qubits with the best qubits having T1≥110 μs. Moreover, our analysis places bounds on energy decay rates for three fabrication-related loss channels present in state-of-the-art superconducting qubits. Understanding dissipation through such systematic analysis may pave the way for lower noise solid state quantum computers.
arxiv pdf