Engineering Purely Nonlinear Coupling between Superconducting Qubits Using a Quarton

Ye, Yufeng; Peng, Kaidong; Naghiloo, Mahdi; Cunningham, Gregory; O’Brien, Kevin

doi:10.1103/physrevlett.127.050502

Cited by 14 publications

(15 citation statements)

References 48 publications

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“…Further, restricting to linear engineered dissipation while designing our protocols also makes them amenable to current experimental techniques in several platforms such as superconducting circuits [53], trapped ions [54] and atoms [55], and optomechanical systems [56]. Specifically, parametrically-coupled circuit-QED systems provide a promising direction for implementation of our protocol, since significant control over the form, amplitudes, and phases of the various interaction terms in the Hamiltonian will be crucial to implementing the desired system Hamiltonian [57][58][59]. A specific example can be found in our recent work [19], where dissipative stabilization of a Bell state was performed in a parametric circuit-QED system with engineered linear dissipation realized via pumping qubit-resonator sidebands.…”

Section: Discussionmentioning

confidence: 99%

Scalable entanglement stabilization with modular reservoir engineering

Doucet¹,

Govia²,

Kamal³

2023

Preprint

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Dissipation engineering is a powerful framework for quantum state preparation and autonomous error correction in few-qubit systems. In this work, we examine the scalability of this approach and give three criteria which any dissipative state stabilization protocol should satisfy to be truly scalable as the number of qubits grows. Besides the requirement that it can be constructed in a resource-efficient manner from simple-to-engineer building blocks, a scalable protocol must also exhibit favorable scaling of the stabilization time with the increase in system size. We present a family of protocols which employ fixed-depth qubit-qubit interactions alongside engineered linear dissipation to stabilize an N -qubit W state. We find that a modular approach to dissipation engineering, with several overlapping few-qubit dissipators rather than a single N -qubit dissipator, is essential for our protocol to be scalable. With this approach, as the number of qubits increases our protocol exhibits low-degree polynomial scaling of the stabilization time and linear growth of the number of control drives in the best case. While the proposed protocol is most easily accessible with current state-of-the-art circuit-QED architectures, the modular dissipation engineering approach presented here can be readily adapted to other platforms and for stabilization of other interesting quantum states.

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Section: Discussionmentioning

confidence: 99%

Scalable entanglement stabilization with modular reservoir engineering

Doucet¹,

Govia²,

Kamal³

2023

Preprint

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“…The anharmonicity of the unimon at flux bias Φ diff = Φ 0 /2 has an opposite sign to that of the transmon, which may be helpful to suppress the unwanted residual Z Z interaction with two-qubit-gate schemes that utilize qubits with opposite-sign anharmoncities 62 , 63 . In analogy to the quarton, the dominance of the quartic term in the potential energy of the unimon may enable extremely fast two-qubit gates and qubit readout in schemes utilizing the unimon as a coupler for transmon qubits 64 . The distributed-element nature of the unimon provides further opportunities for implementing a high connectivity and distant couplings in multi-qubit processors.…”

Section: Discussionmentioning

confidence: 99%

Unimon qubit

et al. 2022

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Superconducting qubits seem promising for useful quantum computers, but the currently wide-spread qubit designs and techniques do not yet provide high enough performance. Here, we introduce a superconducting-qubit type, the unimon, which combines the desired properties of increased anharmonicity, full insensitivity to dc charge noise, reduced sensitivity to flux noise, and a simple structure consisting only of a single Josephson junction in a resonator. In agreement with our quantum models, we measure the qubit frequency, ω01/(2π), and increased anharmonicity α/(2π) at the optimal operation point, yielding, for example, 99.9% and 99.8% fidelity for 13 ns single-qubit gates on two qubits with (ω01, α) = (4.49 GHz, 434 MHz) × 2π and (3.55 GHz, 744 MHz) × 2π, respectively. The energy relaxation seems to be dominated by dielectric losses. Thus, improvements of the design, materials, and gate time may promote the unimon to break the 99.99% fidelity target for efficient quantum error correction and possible useful quantum advantage with noisy systems.

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“…with F = q2 1 + p2 1 + q2 2 + p2 2 − 2 + q1 p2 − p1 q2 . Although we do not have a concrete proposal to realize this gate, we point out that tunable quartic Hamiltonians can be realized in microwave cavities [5,98,99].…”

Section: B Gatesmentioning

confidence: 99%

“…In microwave cavities, this gate could be realized with a tunable cross-Kerr coupling [98,99], assuming that higher order nonlinearities are negligible. We could also realize a √ H in an envelope-preserving manner since the H is based on a lattice isometry.…”

Section: B Gatesmentioning

confidence: 99%

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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Engineering Purely Nonlinear Coupling between Superconducting Qubits Using a Quarton

Cited by 14 publications

References 48 publications

Scalable entanglement stabilization with modular reservoir engineering

Scalable entanglement stabilization with modular reservoir engineering

Unimon qubit

Encoding qubits in multimode grid states

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