Coherence Limits in Interference-Based cos(2 phi) Qubits
The study investigates a cos(2φ) qubit implemented using interferences between two Josephson elements in a SQUID loop. It shows how this design protects against energy relaxation by leveraging wavefunction symmetry, achieving better protection than transmons. However, there is a fundamental trade-off: maximizing protection against energy loss limits coherence time due to unavoidable charge and flux noise dephasing channels.