M. Selvanayagam

Wideband Josephson Parametric Isolator

  1. M. A. Beck,
  2. M. Selvanayagam,
  3. A. Carniol,
  4. S. Cairns,
  5. and C. P. Mancini
The cryogenic hardware needed to build a superconducting qubit based quantum computer requires a variety of microwave components including microwave couplers, filters, amplifiers, and
circulators/isolators. Traditionally, these are implemented via discrete components inserted in to the signal path. As qubit counts climb over the 100+ mark, the integration of these peripheral components, in an effort to reduce overall footprint, thermal load, and added noise in the overall system, is a key challenge to scaling. Ferrite-based microwave isolators are one of the physically largest devices that continue to remain as discrete components. They are generally employed in the readout chain to protect qubits and resonators from broadband noise and unwanted signals emanating from downstream components such as amplifiers. Here we present an alternative two-port isolating integrated circuit derived from the DC Superconducting Quantum Interference Device (DC-SQUID). The non-reciprocal transmission is achieved using the three-wave microwave mixing properties of a flux-modulated DC-SQUID. We show experimentally that, when multiple DC-SQUIDs are embedded in a multi-pole admittance inverting filter structure, RF flux pumping of the DC-SQUIDs can provide directional microwave power flow. For a three-pole filter device, we experimentally demonstrate a directionality greater than 15 dB over a 600 MHz bandwidth.
arxiv pdf

Demonstration of Universal Parametric Entangling Gates on a Multi-Qubit Lattice

  1. M. Reagor,
  2. C. B. Osborn,
  3. N. Tezak,
  4. A. Staley,
  5. G. Prawiroatmodjo,
  6. M. Scheer,
  7. N. Alidoust,
  8. E. A. Sete,
  9. N. Didier,
  10. M. P. da Silva,
  11. E. Acala,
  12. J. Angeles,
  13. A. Bestwick,
  14. M. Block,
  15. B. Bloom,
  16. A. Bradley,
  17. C. Bui,
  18. S. Caldwell,
  19. L. Capelluto,
  20. R. Chilcott,
  21. J. Cordova,
  22. G. Crossman,
  23. M. Curtis,
  24. S. Deshpande,
  25. T. El Bouayadi,
  26. D. Girshovich,
  27. S. Hong,
  28. A. Hudson,
  29. P. Karalekas,
  30. K. Kuang,
  31. M. Lenihan,
  32. R. Manenti,
  33. T. Manning,
  34. J. Marshall,
  35. Y. Mohan,
  36. W. O'Brien,
  37. J. Otterbach,
  38. A. Papageorge,
  39. J.-P. Paquette,
  40. M. Pelstring,
  41. A. Polloreno,
  42. V. Rawat,
  43. C. A. Ryan,
  44. R. Renzas,
  45. N. Rubin,
  46. D. Russell,
  47. M. Rust,
  48. D. Scarabelli,
  49. M. Selvanayagam,
  50. R. Sinclair,
  51. R. Smith,
  52. M. Suska,
  53. T.-W. To,
  54. M. Vahidpour,
  55. N. Vodrahalli,
  56. T. Whyland,
  57. K. Yadav,
  58. W. Zeng,
  59. and C. T. Rigetti
We show that parametric coupling techniques can be used to generate selective entangling interactions for multi-qubit processors. By inducing coherent population exchange between adjacent
qubits under frequency modulation, we implement a universal gateset for a linear array of four superconducting qubits. An average process fidelity of =93% is measured by benchmarking three two-qubit gates with quantum process tomography. In order to test the suitability of these techniques for larger computations, we prepare a six-qubit register in all possible bitstring permutations and monitor the performance of a two-qubit gate on another pair of qubits. Across all these experiments, an average fidelity of =91.6±2.6% is observed. These results thus offer a path to a scalable architecture with high selectivity and low crosstalk.
arxiv pdf

Parametrically-Activated Entangling Gates Using Transmon Qubits

  1. S. Caldwell,
  2. N. Didier,
  3. C. A. Ryan,
  4. E. A. Sete,
  5. A. Hudson,
  6. P. Karalekas,
  7. R. Manenti,
  8. M. Reagor,
  9. M. P. da Silva,
  10. R. Sinclair,
  11. E. Acala,
  12. N. Alidoust,
  13. J. Angeles,
  14. A. Bestwick,
  15. M. Block,
  16. B. Bloom,
  17. A. Bradley,
  18. C. Bui,
  19. L. Capelluto,
  20. R. Chilcott,
  21. J. Cordova,
  22. G. Crossman,
  23. M. Curtis,
  24. S. Deshpande,
  25. T. El Bouayadi,
  26. D. Girshovich,
  27. S. Hong,
  28. K. Kuang,
  29. M. Lenihan,
  30. T. Manning,
  31. J. Marshall,
  32. Y. Mohan,
  33. W. O'Brien,
  34. C. Osborn,
  35. J. Otterbach,
  36. A. Papageorge,
  37. J.-P. Paquette,
  38. M. Pelstring,
  39. A. Polloreno,
  40. G. Prawiroatmodjo,
  41. V. Rawat,
  42. R. Renzas,
  43. N. Rubin,
  44. D. Russell,
  45. M. Rust,
  46. D. Scarabelli,
  47. M. Scheer,
  48. M. Selvanayagam,
  49. R. Smith,
  50. A. Staley,
  51. M. Suska,
  52. N. Tezak,
  53. T.-W. To,
  54. M. Vahidpour,
  55. N. Vodrahalli,
  56. T. Whyland,
  57. K. Yadav,
  58. W. Zeng,
  59. and C. Rigetti
We propose and implement a family of entangling qubit operations activated by radio-frequency flux pulses. By parametrically modulating the frequency of a tunable transmon, these operations
selectively actuate resonant exchange of excitations with a statically coupled, but otherwise off-resonant, neighboring transmon. This direct exchange of excitations between qubits obviates the need for mediator qubits or resonator modes, and it allows for the full utilization of all qubits in a scalable architecture. Moreover, we are able to activate three highly-selective resonances, corresponding to two different classes of entangling gates that enable universal quantum computation: an iSWAP and a controlled-Z rotation. This selectivity is enabled by resonance conditions that depend both on frequency and amplitude, and is helpful in avoiding frequency crowding in a scalable architecture. We report average process fidelities of F = 0.93 for a 135 ns iSWAP, and F = 0.92 for 175 ns and 270 ns controlled-Z operations.
arxiv pdf