Hardware-Encoding Grid States in a Nonreciprocal Superconducting Circuit

Rymarz, Martin; Bosco, Stefano; Ciani, Alessandro; DiVincenzo, David P.

doi:10.1103/physrevx.11.011032

Cited by 41 publications

(37 citation statements)

References 102 publications

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“…Our system presents another potential platform to implement this regime in circuit QED in additional to those proposed using dynamic control [46,47]. Strong coupling of Josephson circuits with low-loss non-reciprocal elements can even produce degenerate and protected ground states for robust encoding of qubits [48]. When all domains are oriented to ± z-axis with net magnetization of zero, the permeability is calculated to be .…”

Section: Discussionmentioning

confidence: 99%

A low-loss ferrite circulator as a tunable chiral quantum system

Wang¹,

Geldern²,

Connolly³

et al. 2021

Preprint

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Ferrite microwave circulators allow one to control the directional flow of microwave signals and noise, and thus play a crucial role in present-day superconducting quantum technology. They are typically viewed as a black-box, and their internal structure is not specified, let alone used as a resource. In this work, we demonstrate a low-loss waveguide circulator constructed with single-crystalline yttrium iron garnet (YIG) in a 3D cavity, and analyze it as a multi-mode hybrid quantum system with coupled photonic and magnonic excitations. We show the coherent coupling of its chiral internal modes with integrated superconducting niobium cavities, and how this enables tunable non-reciprocal interactions between the intra-cavity photons. We also probe experimentally the effective non-Hermitian dynamics of this system and its effective non-reciprocal eigenmodes. The device platform provides a test bed for implementing non-reciprocal interactions in open-system circuit QED.

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Section: Discussionmentioning

confidence: 99%

A low-loss ferrite circulator as a tunable chiral quantum system

Wang¹,

Geldern²,

Connolly³

et al. 2021

Preprint

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“…It was already pointed out that single-mode GKP code words are similar to the Landau levels of an electron in a two-dimensional plane with a uniform magnetic field. Correspondingly, translations in phase space are similar to magnetic translation operators [18,67]. Carrying this comparison further, the gauge µ µ µ we defined in this section plays a role similar to the electromagnetic gauge fields, which should be taken into account when considering physical symmetries of the electronic system [68].…”

Section: Gauge Choicesmentioning

confidence: 97%

Encoding qubits in multimode grid states

Royer,

Singh,

Girvin

2022

Preprint

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Encoding logical quantum information in harmonic oscillator modes is a promising and hardwareefficient approach to the realization of a quantum computer. In this work, we propose to encode logical qubits in grid states of an ensemble of harmonic oscillator modes. We first discuss general results about these multimode bosonic codes; how to design them, how to practically implement them in different experimental platforms and how lattice symmetries can be leveraged to perform logical non-Clifford operations. We then introduce in detail two two-mode grid codes based on the hypercubic and D4 lattices, respectively, showing how to perform a universal set of logical operations. We demonstrate numerically that multimode grid codes have, compared to their singlemode counterpart, increased robustness against propagation of errors from ancillas used for error correction. Finally, we highlight some interesting links between multidimensional lattices and singlemode grid codes concatenated with qubit codes.

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“…As another class of examples, we consider the Lagrangian of a so-called nonreciprocal electric circuit which involve gyrators or circulators [39][40][41]. Such elements can be obtained through active driving [42] or coupling to a magnetic field [43].…”

Section: Non-time-reversal Invariant Hamiltoniansmentioning

confidence: 99%

Stoquasticity in circuit QED

Ciani

Terhal

2021

Phys. Rev. A

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We analyze whether circuit QED Hamiltonians are stoquastic, focusing on systems of coupled flux qubits. We show that scalable sign-problem-free path integral Monte Carlo simulations can typically be performed for such systems. Despite this, we corroborate the recent finding [I. Ozfidan et al., Phys. Rev. Appl. 13, 034037 (2020)] that an effective, nonstoquastic qubit Hamiltonian can emerge in a system of capacitively coupled flux qubits. We find that if the capacitive coupling is sufficiently small, this nonstoquasticity of the effective qubit Hamiltonian can be avoided if we perform a canonical transformation prior to projecting onto an effective qubit Hamiltonian. Our results shed light on the power of circuit QED Hamiltonians for the use of quantum adiabatic computation and the subtlety of finding a representation which cures the sign problem in these systems.

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Hardware-Encoding Grid States in a Nonreciprocal Superconducting Circuit

Cited by 41 publications

References 102 publications

A low-loss ferrite circulator as a tunable chiral quantum system

A low-loss ferrite circulator as a tunable chiral quantum system

Encoding qubits in multimode grid states

Stoquasticity in circuit QED

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