Akshay Gaikwad

Quantum SWAP gate realized with CZ and iSWAP gates in a superconducting architecture

  1. Christian Križan,
  2. Janka Biznárová,
  3. Liangyu Chen,
  4. Emil Hogedal,
  5. Amr Osman,
  6. Christopher W. Warren,
  7. Sandoko Kosen,
  8. Hang-Xi Li,
  9. Tahereh Abad,
  10. Anuj Aggarwal,
  11. Marco Caputo,
  12. Jorge Fernández-Pendás,
  13. Akshay Gaikwad,
  14. Leif Grönberg,
  15. Andreas Nylander,
  16. Robert Rehammar,
  17. Marcus Rommel,
  18. Olga I. Yuzephovich,
  19. Anton Frisk Kockum,
  20. Joonas Govenius,
  21. Giovanna Tancredi,
  22. and Jonas Bylander
It is advantageous for any quantum processor to support different classes of two-qubit quantum logic gates when compiling quantum circuits, a property that is typically not seen with
existing platforms. In particular, access to a gate set that includes support for the CZ-type, the iSWAP-type, and the SWAP-type families of gates, renders conversions between these gate families unnecessary during compilation as any two-qubit Clifford gate can be executed using at most one two-qubit gate from this set, plus additional single-qubit gates. We experimentally demonstrate that a SWAP gate can be decomposed into one iSWAP gate followed by one CZ gate, affirming a more efficient compilation strategy over the conventional approach that relies on three iSWAP or three CZ gates to replace a SWAP gate. Our implementation makes use of a superconducting quantum processor design based on fixed-frequency transmon qubits coupled together by a parametrically modulated tunable transmon coupler, extending this platform’s native gate set so that any two-qubit Clifford unitary matrix can be realized using no more than two two-qubit gates and single-qubit gates.
arxiv pdf

Deterministic generation of frequency-bin-encoded microwave photons

  1. Jiaying Yang,
  2. Maryam Khanahmadi,
  3. Ingrid Strandberg,
  4. Akshay Gaikwad,
  5. Claudia Castillo Moreno,
  6. Anton Frisk Kockum,
  7. Muhammad Asad Ullah,
  8. Göran Johansson,
  9. Axel Martin Eriksson,
  10. and Simone Gasparinetti
A distributed quantum computing network requires a quantum communication channel between spatially separated processing units. In superconducting circuits, such a channel can be implemented
based on propagating microwave photons to encode and transfer quantum information between an emitter and a receiver. However, traveling microwave photons can be lost during the transmission, leading to the failure of information transfer. Heralding protocols can be used to detect such photon losses. In this work, we propose such a protocol and experimentally demonstrate a frequency-bin encoding method of microwave photonic modes using superconducting circuits. We deterministically encode the quantum information from a superconducting qubit by simultaneously emitting its information into two photonic modes at different frequencies, with a process fidelity of 90.4%. The frequency-bin-encoded photonic modes can be used, at the receiver processor, to detect the occurrence of photon loss. Our work thus provides a reliable method to implement high-fidelity quantum state transfer in a distributed quantum computing network, incorporating error detection to enhance performance and accuracy.
arxiv pdf