Abstract: A microwave filter includes a multilayer stack. The multilayer stack includes one or more first-type layers composed of a first superconductor material having a first superconducting critical temperature; and one or more second-type layers composed of a non-superconductor metal or a second superconductor material having a second superconducting critical temperature that is lower than the first superconducting critical temperature. The multilayer stack is configured to behave as a dissipative metal for photons having a frequency above twice a superconducting gap frequency of the multilayer stack and to behave as a superconductor for photons having a frequency below twice the superconducting gap frequency of the multilayer stack.

Abstract: A quantum computer architecture employs logical qubits that are constructed from a concatenation of doubly periodic Josephson junction circuits. The series concatenation of the doubly periodic Josephson junction circuits provides exponential robustness against local noise. It is possible to perform discrete Clifford group rotations and entangling operations on the logical qubits without leaving the protected state.

Abstract: A quantum computer architecture employs logical qubits that are constructed from a concatenation of doubly periodic Josephson junction circuits. The series concatenation of the doubly periodic Josephson junction circuits provides exponential robustness against local noise. It is possible to perform discrete Clifford group rotations and entangling operations on the logical qubits without leaving the protected state.