Demonstrating NISQ Era Challenges in Algorithm Design on IBM's 20 Qubit
  Quantum Computer
As superconducting qubits continue to advance technologically, the
realization of quantum algorithms from theoretical abstraction to physical
implementation requires knowledge of both quantum circuit construction as well
as hardware limitations. In this study we present results from experiments run
on IBM's 20-qubit `Poughkeepsie' architecture, with the goal of demonstrating
various qubit qualities and challenges that arise in designing quantum
algorithms. These include experimentally measuring $T_1$ and $T_2$ coherence
times, gate fidelities, sequential CNOT gates, techniques for handling ancilla
qubits, and finally CCNOT and QFT$^{\dagger}$ circuits implemented on several
different qubit geometries. Our results demonstrate various techniques for
improving quantum circuits which must compensate for limited connectivity,
either through the use of SWAP gates or additional ancilla qubits.
Daniel Koch Brett Martin Saahil Patel Laura Wessing Paul M. Alsing