Hamiltonian Extrema of an Arbitrary Flux-Biased Josephson Circuit
Alessandro Miano, Vidul Joshi, G. Liu, Wenhan Dai, P. D. Parakh, Luigi Frunzio, Michel Devoret · PRX Quantum · 2023
Flux-biased loops including one or more Josephson junctions are ubiquitous elements in quantum information experiments based on superconducting circuits.These quantum circuits can be tuned to implement a variety of Hamiltonians, with applications ranging from decoherence-protected qubits to quantum limited converters and amplifiers.The extrema of the Hamiltonian of these circuits are of special interest because they govern their low-energy dynamics.However, the theory of superconducting quantum circuits so far lacks a systematic method to find these extrema and compute the series expansion of the Hamiltonian in their vicinity for an arbitrary nonlinear superconducting circuit.We present such a method, which can aid the synthesis of new functionalities in quantum devices.