The superconducting fluxonium circuit is an artificial atom with a strongly anharmonic spectrum: When biased at a half flux quantum, the lowest qubit transition is an order of magnitude smaller in frequency than those to higher levels. Similar to conventional atomic systems, such a frequency separation between the computational and noncomputational subspaces allows independent optimizations of the qubit coherence and two-qubit interactions. Here, we describe a controlled- $Z$ gate for two fluxoniums connected either capacitively or inductively, with qubit transitions fixed near $500\phantom{\rule{3.33333pt}{0ex}}\mathrm{MHz}$ . The gate is activated by a microwave drive at a resonance involving the second excited state. We estimate intrinsic gate fidelities over 99.9% with gate times below 100 ns.The superconducting fluxonium circuit is an artificial atom with a strongly anharmonic spectrum: When biased at a half flux quantum, the lowest qubit transition is an order of magnitude smaller in frequency than those to higher levels. Similar to conventional atomic systems, such a frequency separation between the computational and noncomputational subspaces allows independent optimizations of the qubit coherence and two-qubit interactions. Here, we describe a controlled-$Z$ gate for two fluxoniums connected either capacitively or inductively, with qubit transitions fixed near $500\phantom{\rule{3.33333pt}{0ex}}\mathrm{MHz}$. The gate is activated by a microwave drive at a resonance involving the second excited state. We estimate intrinsic gate fidelities over 99.9% with gate times below 100 ns.

arXiv:1802.03095Physical Review ASep 24, 201838 citations

Proposal for Entangling Gates on Fluxonium Qubits via a Two-Photon Transition

Konstantin Nesterov, Quentin Ficheux, Vladimir E. Manucharyan +1 more

We propose a family of microwave-activated entangling gates on two capacitively coupled fluxonium qubits.A microwave pulse applied to either qubit at a frequency near the half-frequency of the |00 -|11 transition induces two-photon Rabi oscillations with a negligible leakage outside the computational subspace, owing to the strong anharmonicity of fluxoniums.By adjusting the drive frequency, amplitude, and duration, we obtain the gate family that is locally equivalent to the fermionic-simulation gates such as √ SWAP-like and controlled-phase gates.The gate error can be tuned below 10 -4 for a pulse duration under 100 ns without excessive circuit parameter matching.Given that the fluxonium coherence time can exceed 1 ms, our gate scheme is promising for large-scale quantum processors.We propose a family of microwave-activated entangling gates on two capacitively coupled fluxonium qubits.A microwave pulse applied to either qubit at a frequency near the half-frequency of the |00 -|11 transition induces two-photon Rabi oscillations with a negligible leakage outside the computational subspace, owing to the strong anharmonicity of fluxoniums.By adjusting the drive frequency, amplitude, and duration, we obtain the gate family that is locally equivalent to the fermionic-simulation gates such as √ SWAP-like and controlled-phase gates.The gate error can be tuned below 10 -4 for a pulse duration under 100 ns without excessive circuit parameter matching.Given that the fluxonium coherence time can exceed 1 ms, our gate scheme is promising for large-scale quantum processors.

arXiv:2011.10011PRX QuantumJun 22, 202124 citations

Fast flux gates in inductively coupled fluxonium qubits

Helin Zhang, Srivatsan Chakram, Tanay Roy +6 more

Bulletin of the American Physical SocietyMar 15, 20210 citations

High-fidelity gates on fluxonium qubits

Quentin Ficheux, Haonan Xiong, Aaron Somoroff +4 more

Bulletin of the American Physical SocietyMar 17, 20210 citations

Z

gate for two fluxoniums connected either capacitively or inductively, with qubit transitions fixed near

500\phantom{\rule{3.33333pt}{0ex}}\mathrm{MHz}

. The gate is activated by a microwave drive at a resonance involving the second excited state. We estimate intrinsic gate fidelities over 99.9% with gate times below 100 ns.