Experimental Realization of a Protected Superconducting Circuit Derived from the 
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–
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 Qubit

Gyenis, András; Mundada, Pranav; Paolo, Agustín Di; Hazard, Thomas; You, Xinyuan; Schuster, David I.; Koch, Jens; Blais, Alexandre; Houck, Andrew

doi:10.1103/prxquantum.2.010339

Cited by 121 publications

(83 citation statements)

References 55 publications

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“…Gate times on the order of 100 ns were demonstrated for various gate types [4], while coherence times exceeding 100 µs were reported for transmon qubits [5]. The possibilities of the further improvement of coherence times were demonstrated using novel qubit designs, such as a fluxonium qubit [6,7], a 0 -π qubit [8], and bosonic qubits [9,10]. However, independent of a particular qubit architecture, coherence times are ultimately limited by intrinsic losses in materials constituting a qubit, and reducing the number of material defects is a crucial factor for the qubit performance improvement [5,11,12].…”

Section: Introductionmentioning

confidence: 99%

Identification of different types of high-frequency defects in superconducting qubits

Abdurakhimov¹,

Mahboob²,

Toida³

et al. 2021

Preprint

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Section: Introductionmentioning

confidence: 99%

Identification of different types of high-frequency defects in superconducting qubits

Abdurakhimov¹,

Mahboob²,

Toida³

et al. 2021

Preprint

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“…The ideal cos 2φ circuit preserves the Cooper-pair parity symmetry via a special type of Josephson junction that only permits the tunneling of pairs of Cooper pairs. Considerable progress has been made towards effectively realizing double-Cooper-pair junctions by a variety of approaches [13][14][15][16][17][18][19][20]. Improving robustness of the cos 2φ qubit by constructing arrays that average uncorrelated local noise has also been investigated [3,[20][21][22][23][24][25].…”

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confidence: 99%

Protected hybrid superconducting qubit in an array of gate-tunable Josephson interferometers

Schrade¹,

Marcus²,

Gyenis³

2021

Preprint

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We propose a protected qubit based on a modular array of superconducting islands connected by semiconductor Josephson interferometers. The individual interferometers realize effective cos 2φ elements that exchange 'pairs of Cooper pairs' between the superconducting islands when gate-tuned into balance and frustrated by a half flux quantum. If a large capacitor shunts the ends of the array, the circuit forms a protected qubit because its degenerate ground states are robust to offset charge and magnetic field fluctuations for a sizable window around zero offset charge and half flux quantum. This protection window broadens upon increasing the number of interferometers if the individual elements are balanced. We use an effective spin model to describe the system and show that a quantum phase transition point sets the critical flux value at which protection is destroyed.

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“…A relevant example is provided by the 4π Josephson effect in topological superconductors [35], where a cosðφ=2Þ relation describes single electron tunneling via Majorana zero energy states localized at the junction. Likewise, second-harmonic Josephson energyphase relations describe tunneling of pairs of Cooper pairs at the junction and several instances have been recently proposed [36,37]. An effective cosð2φÞ is realized in parity-protected semiconductor-superconductor qubits [38] through gatemons [39,40], based on semiconducting wires [41,42], or can be obtained by using four nominally equal JJs in a rhombus configuration [43][44][45][46][47].…”

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confidence: 99%

Enhanced Coherence in Superconducting Circuits via Band Engineering

Chirolli

Moore

2021

Phys. Rev. Lett.

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In superconducting circuits interrupted by Josephson junctions, the dependence of the energy spectrum on offset charges on different islands is 2e periodic through the Aharonov-Casher effect and resembles a crystal band structure that reflects the symmetries of the Josephson potential. We show that higherharmonic Josephson elements described by a cosð2φÞ energy-phase relation provide an increased freedom to tailor the shape of the Josephson potential and design spectra featuring multiplets of flat bands and Dirac points in the charge Brillouin zone. Flat bands provide noise-insensitive energy levels, and consequently, engineering band pairs with flat spectral gaps can help improve the coherence of the system. We discuss a modified version of a flux qubit that achieves, in principle, no decoherence from charge noise and introduce a flux qutrit that shows a spin-1 Dirac spectrum and is simultaneously quite robust to both charge and flux noise.

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Experimental Realization of a Protected Superconducting Circuit Derived from the 0 – π Qubit

Cited by 121 publications

References 55 publications

Identification of different types of high-frequency defects in superconducting qubits

Identification of different types of high-frequency defects in superconducting qubits

Protected hybrid superconducting qubit in an array of gate-tunable Josephson interferometers

Enhanced Coherence in Superconducting Circuits via Band Engineering

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