scqubits is a Python library for designing and analyzing superconducting qubit systems. Simulate circuit quantization for transmons, fluxoniums, and custom circuits; compute eigenspectra and transition frequencies; model couplings and parameter sweeps; study anharmonicity and dispersive shifts. Used for hardware design, qubit characterization, and optimizing circuit parameters.
A superconducting qubit is a nonlinear oscillator built from Josephson junctions and capacitances. scqubits starts with the classical circuit (schematic), performs circuit quantization to derive the quantum Hamiltonian, then solves for energy levels and matrix elements. Understanding your qubit's Hamiltonian is essential for gate design and noise characterization.
from scqubits import * # Transmon qubit: two junctions, two capacitors transmon = Transmon( EJ=15.0, # Josephson energy (GHz) EC=0.3, # Charging energy (GHz) ng=0.0, # Offset charge ncut=30 # Hilbert space cutoff ) # Compute first few energy levels eigenvals = transmon.eigenvals(n=5) print(eigenvals) # Anharmonicity (difference between transition frequencies) print(transmon.anharmonicity())
scqubits handles the Hamiltonian and spectral analysis; pair with Qiskit for gate construction or QuTiP for dynamics simulation.