---
res:
  bibo_abstract:
  - "An ideal quantum computer relies on qubits capable of performing fast gate operations
    and\r\nmaintaining strong interconnections while preserving their quantum coherence.
    Since the\r\ninception of experimental eforts toward building a quantum computer,
    the community has\r\nfaced challenges in engineering such a system. Among the
    various methods of implementing a\r\nquantum computer, superconducting qubits
    have shown fast gates close to tens of nanoseconds,\r\nwith the state-of-the-art
    reaching a coherence of a few milliseconds. However, achieving\r\nsimultaneously
    long lifetimes with fast qubit operations poses an inherent paradox. Qubits\r\nwith
    high coherence require isolation from the environment, while fast operation necessitates\r\nstrong
    coupling of the qubit. This thesis approaches this issue by proposing the idea
    of\r\nengineering superconducting qubits capable of transitioning between operating
    in a protected\r\nregime, where the qubit is completely isolated from the environment,
    and coupling to the\r\ncommunication channels as needed. In this direction, we
    use the geometric superinductor to\r\nscan the parameter space of rf-SQUID devices,
    searching for a regime where we can take the\r\nqubit protection to its extreme.\r\n\r\nThis
    leads us to the inductively shunted transmon (IST) regime, characterized by EJ
    /EC ≫ 1\r\nand EJ /EL ≫ 1, where the circuit potential exhibits a double well
    with a large barrier\r\nseparating the local ground states of each quantum well.
    In this regime, although it is\r\nanticipated that the two quantum wells would
    be isolated from each other, we observe single\r\nfuxon tunneling between them.
    The interplay of the cavity photons and the fuxon transition\r\nforms a rich physical
    system, containing resonance conditions that allow the preparation of the\r\nfuxon
    ground or excited states. This enables us to study the relaxation rate of such
    transition\r\nand show that it can be as large as 3.6 hours. Dynamically controlling
    the barrier height\r\nbetween the two quantum wells allows for controllable coupling,
    which scales exponentially,\r\nfor a qubit encoded in two fuxon states.\r\nThe
    0-π qubit is one of the very few known superconducting circuit types that ofers
    exponential\r\nprotection from both relaxation and dephasing simultaneously. However,
    this qubit is not\r\nexempt from the fact that such protection comes at the expense
    of complex readout and\r\ncontrol. In this thesis, we propose a way to controllably
    break the circuit symmetry, the\r\nkey reason for the protection, to momentarily
    restore the ability to control and manipulate\r\nthe qubit. An asymmetry in capacitances
    and inductances in the 0-π circuit is detrimental\r\nsince they lead to coupling
    of the protected state to the thermally occupied parasitic mode\r\nof the circuit.
    However, here we try to exploit a controlled asymmetry in Josephson energies\r\nand
    show that this can be used as a tunable coupler between the protected states.
    In the\r\nfuture, this should allow to perform gate operations by dynamically
    controlling the asymmetry\r\ninstead of driving the protected transition with
    microwave pulses. Therefore, we believe that\r\nthe proposed method can make the
    use of protected qubits more practical in experimental\r\nrealizations of quantum
    computing.@eng"
  bibo_authorlist:
  - foaf_Person:
      foaf_givenName: Farid
      foaf_name: Hassani, Farid
      foaf_surname: Hassani
      foaf_workInfoHomepage: http://www.librecat.org/personId=2AED110C-F248-11E8-B48F-1D18A9856A87
    orcid: 0000-0001-6937-5773
  bibo_doi: 10.15479/at:ista:17133
  dct_date: 2024^xs_gYear
  dct_isPartOf:
  - http://id.crossref.org/issn/2663-337X
  - http://id.crossref.org/issn/978-3-99078-040-4
  dct_language: eng
  dct_publisher: Institute of Science and Technology Austria@
  dct_subject:
  - Quantum information
  - Qubits
  - Superconducting devices
  dct_title: Superconducting qubits capable of dynamic switching between protected
    and high-speed control regimes@
...