Sampling and scrambling on a chain of superconducting qubits

Understand

We study a circuit, the Josephson sampler, that embeds a real vector into an entangled state of n qubits, and optionally samples from it.

• We measure its fidelity and entanglement on the 16-qubit ibmqx5 chip.
• To assess its expressiveness, we also measure its ability to generate Haar random unitaries and quantum chaos, as measured by Porter-Thomas statistics and out-of-time-order correlation functions.
• The circuit requires nearest-neighbor CZ gates on a chain and is especially well suited for first-generation superconducting architectures.