@article { WOS:000648494200001,
title = {Fast Logic with Slow Qubits: Microwave-Activated Controlled-Z Gate on Low-Frequency Fluxoniums},
journal = {Phys. Rev. X},
volume = {11},
number = {2},
year = {2021},
month = {MAY 3},
publisher = {AMER PHYSICAL SOC},
type = {Article},
abstract = {We demonstrate a controlled-Z gate between capacitively coupled fluxonium qubits with transition frequencies 72.3 and 136.3 MHz. The gate is activated by a 61.6-ns-long pulse at a frequency between noncomputational transitions vertical bar 10 > - vertical bar 20 > and vertical bar 11 > - vertical bar 21 >, during which the qubits complete only four and eight Larmor periods, respectively. The measured gate error of (8 +/- 1) x 10(-3) is limited by decoherence in the noncomputational subspace, which will likely improve in the next-generation devices. Although our qubits are about 50 times slower than transmons, the two-qubit gate is faster than microwave-activated gates on transmons, and the gate error is on par with the lowest reported. Architectural advantages of lowfrequency fluxoniums include long qubit coherence time, weak hybridization in the computational subspace, suppressed residual ZZ-coupling rate (here 46 kHz), and the absence of either excessive parameter-matching or complex pulse-shaping requirements.},
issn = {2160-3308},
doi = {10.1103/PhysRevX.11.021026},
author = {Ficheux, Quentin and Nguyen, Long B. and Somoroff, Aaron and Xiong, Haonan and Nesterov, Konstantin N. and Vavilov, Maxim G. and Manucharyan, Vladimir E.}
}
@article { WOS:000674761000001,
title = {Proposal for Entangling Gates on Fluxonium Qubits via a Two-Photon Transition},
journal = {PRX Quantum},
volume = {2},
number = {2},
year = {2021},
month = {JUN 22},
publisher = {AMER PHYSICAL SOC},
type = {Article},
abstract = {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 vertical bar 00 >-vertical bar 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 root 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.},
doi = {10.1103/PRXQuantum.2.020345},
author = {Nesterov, Konstantin N. and Ficheux, Quentin and Manucharyan, Vladimir E. and Vavilov, Maxim G.}
}
@article { ISI:000532064500001,
title = {Counting statistics of microwave photons in circuit QED},
journal = {Phys. Rev. A},
volume = {101},
number = {5},
year = {2020},
month = {MAY 13},
pages = {052321},
publisher = {AMER PHYSICAL SOC},
type = {Article},
abstract = {In superconducting circuit architectures for quantum computing, microwave resonators are often used both to isolate qubits from the electromagnetic environment and to facilitate qubit state readout. We analyze the full counting statistics of photons emitted from such driven readout resonators both in and beyond the dispersive approximation. We calculate the overlap between emitted-photon distributions for the two qubit states and explore strategies for its minimization with the purpose of increasing fidelity of intensity-sensitive readout techniques. In the dispersive approximation and at negligible qubit relaxation, both distributions are Poissonian, and the overlap between them can be easily made arbitrarily small. Nondispersive terms of the Hamiltonian generate squeezing and the Purcell decay with the latter effect giving the dominant contribution to the overlap between two distributions.},
issn = {2469-9926},
doi = {10.1103/PhysRevA.101.052321},
author = {Nesterov, Konstantin N. and Pechenezhskiy, V, Ivan and Vavilov, Maxim G.}
}
@article { ISI:000445503000001,
title = {Microwave-activated controlled-Z gate for fixed-frequency fluxonium qubits},
journal = {PHYSICAL REVIEW A},
volume = {98},
number = {3},
year = {2018},
month = {SEP 24},
pages = {030301},
issn = {2469-9926},
doi = {10.1103/PhysRevA.98.030301},
author = {Nesterov, Konstantin N. and Pechenezhskiy, V, Ivan and Wang, Chen and Manucharyan, Vladimir E. and Vavilov, Maxim G.}
}