A Quantum Instruction Set Implemented on a Superconducting Quantum Processor

  1. M. Kjaergaard,
  2. M. E. Schwartz,
  3. A. Greene,
  4. G. O. Samach,
  5. A. Bengtsson,
  6. M. O'Keeffe,
  7. C. M. McNally,
  8. J. Braumüller,
  9. D. K. Kim,
  10. P. Krantz,
  11. M. Marvian,
  12. A. Melville,
  13. B. M. Niedzielski,
  14. Y. Sung,
  15. R. Winik,
  16. J. Yoder,
  17. D. Rosenberg,
  18. K. Obenland,
  19. S. Lloyd,
  20. T. P. Orlando,
  21. I. Marvian,
  22. S. Gustavsson,
  23. and W. D. Oliver
A quantum algorithm consists of a sequence of operations and measurements applied to a quantum processor. To date, the instruction set which defines this sequence has been provided
by a classical computer and passed via control hardware to the quantum processor. Here, we demonstrate the first experimental realization of a quantum instruction set, in which a fixed sequence of classically-defined gates perform an operation that is fully determined only by a quantum input to the fixed sequence. Specifically, we implement the density matrix exponentiation algorithm, which consumes N copies of the instruction state ρ to approximate the operation e−iρθ (θ an arbitrary angle). Our implementation relies on a 99.7\% fidelity controlled-phase gate between two superconducting transmon qubits. We achieve an average algorithmic fidelity ≈0.9, independent of the setting of ρ, to circuit depth nearly 90. This new paradigm for quantum instructions has applications to resource-efficient protocols for validating entanglement spectra, principal component analysis of large quantum states, and universal quantum emulation.