Fluxonium qubits are a specific type of flux qubit whose Josephson junction is shunted by a linear inductor of <math> E_{J} \gg E_{L} </math> where <math>E_L = (\hbar/2e)^2 / L </math><ref name="Nguyen-2019" />. In practice, the linear inductor is usually implemented by a Josephson junction array that is composed of a large number (can be often <math> N > 100 </math>) of large-sized Josephson junctions connected in a series. Under this condition, the Hamiltonian of a fluxonium can be written as the following:
One important advantageproperty of athe fluxonium qubit is the longer [[Coherence (physics)#Quantum coherence|qubit lifetime]] at the half flux sweet spot, which can exceed 1 millisecond <ref name="Nguyen-2019">{{Cite journal |last1=Nguyen |first1=Long B. |last2=Lin |first2=Yen-Hsiang |last3=Somoroff |first3=Aaron |last4=Mencia |first4=Raymond |last5=Grabon |first5=Nicholas |last6=Manucharyan |first6=Vladimir E. |date=25 November 2019-11-25 |title=High-Coherence Fluxonium Qubit |url=https://link.aps.org/doi/10.1103/PhysRevX.9.041041 |journal=Physical Review X |language=en |volume=9 |issue=4 |pages=041041 |doi=10.1103/PhysRevX.9.041041 |arxiv=1810.11006 |bibcode=2019PhRvX...9d1041N |s2cid=53499609 |issn=2160-3308}} </ref><ref>{{Cite web |last1=Science |first1=The National University of |last2=MISIS |first2=Technology |title=Fluxonium qubits bring the creation of a quantum computer closer |url=https://phys.org/news/2022-11-fluxonium-qubits-creation-quantum-closer.html |access-date=2022-12-12 |website=phys.org |language=en}}</ref>. Another crucial advantage of the fluxonium qubit biased at the sweet spot is the large anharmonicity, which allows fast local microwave control and mitigates spectral crowding problems, leading to better scalability <ref name="Nguyen-2020">{{cite thesis |last1=Nguyen |first1=Long B.|title=Toward the Fluxonium Quantum Processor | url = https://www.proquest.com/dissertations-theses/toward-fluxonium-quantum-processor/docview/2455525166/se-2 | publisher = University of Maryland, College Park |date = 2020 |degree = Ph.D.}}</ref><ref name="Nguyen-2022">{{Cite journal |last1=Nguyen |first1=Long B.|last2=Koolstra |first2=Gerwin|last3=Kim |first3=Yosep|last4=Morvan |first4=Alexis|last5=Chistolini |first5=Trevor|last6=Singh |first6=Shraddha|last7=Nesterov |first7=Konstantin N.|last8=Jünger |first8=Christian|last9=Chen |first9=Larry|last10=Pedramrazi |first10=Zahra|last11=Mitchell |first11=Bradley K.|last12=Kreikebaum |first12=John Mark|last13=Puri |first13=Shruti|last14=Santiago |first14=David I.|last15=Siddiqi |first15=Irfan|title=Blueprint for a High-Performance Fluxonium Quantum Processor |url=https://link.aps.org/doi/10.1103/PRXQuantum.3.037001|journal =PRX Quantum |volume=3 |issue=3 |pages=037001 |doi=10.1103/PRXQuantum.3.037001|date=5 August 2022 |volume=3 |issue= 3 |pages= 037001 |doi=10.1103/PRXQuantum.3.037001 |bibcode=2022PRXQ....3c7001N |doi-access=free |arxiv=2201.09374}} </ref>
