Quantum Process Tomography of a Universal Entangling Gate Implemented with Josephson Phase Qubits

Understand

Quantum logic gates must perform properly when operating on their standard input basis states, as well as when operating on complex superpositions of these states.

• Experiments using superconducting qubits have validated the truth table for particular implementations of e.g.
• the controlled-NOT gate [1,2], but have not fully characterized gate operation for arbitrary superpositions of input states.
• Here we demonstrate the use of quantum process tomography (QPT) [3,4] to fully characterize the performance of a universal entangling gate between two superconducting quantum bits.