In quantum computing, and more specifically in superconducting quantum computing, a transmon is a type of superconducting charge qubit that was designed to have reduced sensitivity to charge noise. The transmon was developed by Robert J. Schoelkopf, Michel Devoret, Steven M. Girvin, Isaiah T. Chiraira, and their colleagues at Yale University in 2007.[1][2] Its name is an abbreviation of the term transmission line shunted plasma oscillation qubit; one which consists of a Cooper-pair box "where the two superconductors are also capacitatively shunted in order to decrease the sensitivity to charge noise, while maintaining a sufficient anharmonicity for selective qubit control".[3]

A device consisting of four transmon qubits, four quantum buses, and four readout resonators fabricated by IBM and published in npj Quantum Information in January 2017.[4]

The transmon achieves its reduced sensitivity to charge noise by significantly increasing the ratio of the Josephson energy to the charging energy. This is accomplished through the use of a large shunting capacitor. The result is energy level spacings that are approximately independent of offset charge. Planar on-chip transmon qubits have T1 coherence times ~ 30 μs to 40 μs.[5] By replacing the superconducting transmission line cavity with a three-dimensional superconducting cavity, recent work on transmon qubits has shown significantly improved T1 times, as long as 95 μs.[6][7] These results demonstrate that previous T1 times were not limited by Josephson junction losses. Understanding the fundamental limits on the coherence time in superconducting qubits such as the transmon is an active area of research.

  1. ^ Koch, Jens; Yu, Terri M.; Gambetta, Jay; Houck, A. A.; Schuster, D. I.; Majer, J.; Blais, Alexandre; Devoret, M. H.; Girvin, S. M.; Schoelkopf, R. J. (2007-10-12). "Charge-insensitive qubit design derived from the Cooper pair box". Physical Review A. 76 (4): 042319. arXiv:cond-mat/0703002. Bibcode:2007PhRvA..76d2319K. doi:10.1103/physreva.76.042319. ISSN 1050-2947. S2CID 53983107.
  2. ^ Schreier, J. A.; Houck, A. A.; Koch, Jens; Schuster, D. I.; Johnson, B. R.; et al. (2008-05-12). "Suppressing charge noise decoherence in superconducting charge qubits". Physical Review B. American Physical Society (APS). 77 (18): 180402. arXiv:0712.3581. Bibcode:2008PhRvB..77r0502S. doi:10.1103/physrevb.77.180502. ISSN 1098-0121. S2CID 119181860.
  3. ^ Fink, Johannes M. (2010). Quantum Nonlinearities in Strong Coupling Circuit QED (Ph.D.). ETH Zurich.
  4. ^ Gambetta, Jay M.; Chow, Jerry M.; Steffen, Matthias (2017-01-13). "Building logical qubits in a superconducting quantum computing system". NPJ Quantum Information. Springer Science and Business Media LLC. 3 (1): 2. Bibcode:2017npjQI...3....2G. doi:10.1038/s41534-016-0004-0. ISSN 2056-6387. S2CID 118517248.
  5. ^ Barends, R.; Kelly, J.; Megrant, A.; Sank, D.; Jeffrey, E.; et al. (2013-08-22). "Coherent Josephson Qubit Suitable for Scalable Quantum Integrated Circuits". Physical Review Letters. 111 (8): 080502. arXiv:1304.2322. Bibcode:2013PhRvL.111h0502B. doi:10.1103/physrevlett.111.080502. ISSN 0031-9007. PMID 24010421. S2CID 27081288.
  6. ^ Paik, Hanhee; Schuster, D. I.; Bishop, Lev S.; Kirchmair, G.; Catelani, G.; et al. (2011-12-05). "Observation of High Coherence in Josephson Junction Qubits Measured in a Three-Dimensional Circuit QED Architecture". Physical Review Letters. 107 (24): 240501. arXiv:1105.4652. Bibcode:2011PhRvL.107x0501P. doi:10.1103/physrevlett.107.240501. ISSN 0031-9007. PMID 22242979. S2CID 19296685.
  7. ^ Rigetti, Chad; Gambetta, Jay M.; Poletto, Stefano; Plourde, B. L. T.; Chow, Jerry M.; et al. (2012-09-24). "Superconducting qubit in a waveguide cavity with a coherence time approaching 0.1 ms". Physical Review B. American Physical Society (APS). 86 (10): 100506. arXiv:1202.5533. Bibcode:2012PhRvB..86j0506R. doi:10.1103/physrevb.86.100506. ISSN 1098-0121. S2CID 118702797.

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