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I am interested in the state of the art gate speeds and decoherence times for the qubit types I know are being pursued by companies presently:

  • superconducting qubits,
  • ion trap qubits,
  • photonic qubits.

Where can I find these, and is there a place where these are updated regularly?

There have been various published tables depicting these times for various types of qubits over the years (including the famous Los Alamos National Lab QC Roadmap), but the numbers always change while the published papers don't.

I needed these numbers to answer this question because I wanted to compare the 1ps decoherence time in the FMO to state-of-the-art decoherence times and gate times in popular candidates for QCs, so I went searching for some reasonable values for roughly this time period, but I don't anymore know where to look.

The longest coherence time ever measured was given in this answer, but no gate times were given: What is the longest time a qubit has survived with 0.9999 fidelity?

James Wootton talked about the advantages and disadvantages of the above three qubit types, but not the gate/decoherence times, in this answer: What is the leading edge technology for creating a quantum computer with the fewest errors?

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2 Answers 2

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I guess your best shot would be to look for experimental comparisons like this one on Arxiv.

But I am not aware of a tracking. I do not think we can consider having a "state of the art" in this field. The goal being to make them always better of course with better connectivity for instance (a possible factor to take into account).

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  • $\begingroup$ Thank you. Where is the gate speed and decoherence times? Connectivity is important, but it's always possible to add more connectivity. Decoherence times and the speed at which you can do gates are a fairly useful thing to know, although not a perfect characterization of the quality of a quantum computer. $\endgroup$
    – user1271772
    Aug 28, 2018 at 4:57
  • $\begingroup$ In the article? So they gave the gate times for single and 2-qubit operations. For decoherence times, you have the T1 and T2 which they call depolarization and dephasing times. I am not a hardware specialist but those times are generally used as benchmarks for hardware characterization. $\endgroup$
    – cnada
    Aug 28, 2018 at 11:31
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    $\begingroup$ Ok for ion traps: "Typical gate times are 20 µs for single- and 250 µs for two-qubit gates. Spin depolarization is negligible for hyperfine ground level qubits (T1 ∼ ∞). The spin-dephasing time (T2) is ∼ 0.5 s in the current setup, and can be easily extended by suppressing magnetic field noise." For IBM: "Typical gate times are 130 ns for single- and 250 − 450 ns for two-qubit gates, while coherence times are ∼ 60 µs for both depolarization (T1) and spin dephasing (T2)." $\endgroup$
    – user1271772
    Aug 28, 2018 at 18:51
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You could also look at the following webpage:

https://quantumcomputingreport.com/scorecards/qubit-quality/

where they provide recent (I'm not sure how often they update this scores) values for gate fidelities and decoherece times for IBM and Rigetti chips (unfortunately they don't give any results on ion traps and photonics, since these machines are not well described by commercial companies).

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