###### While small now, quantum computers are expected to experience exponential growth in size, speed, and accuracy over the coming years. The following plots chart this progress, updated and extrapolated from past performance, and prognosticate a time when quantum computers will be powerful enough to crack digital signatures.

Interactive version here.****
Interactive version here.****
Interactive version here.****

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The above plots reflect growth in superconducting qubit quantum computers. Shown are recent achievements and predictions for: number of qubits, the quantum gate frequency measured in two qubit gate operations per second, and two qubit quantum gate infidelity (error rate). The optimistic curves are based on an exponential growth rate extrapolated, using linear least squares, from technological developments reported up to the current year. The pessimistic curves assume exponential improvement at a rate half the optimistic rate.

###### The last plot shows the predicted Shor time, as a function of development year, for a quantum computer to break the Elliptic Curve Digital Signature Algorithm based on the secp256k1 curve using Shor’s discrete log algorithm (see Roetteler et al. 2017). The calculation includes overheads for a superconducting qubit quantum computer using surface code based quantum error correction. The left dashed line assumes optimistic predications for qubit number, gate frequency, and infidelities above, and the right dashed line assumes the pessimistic predictions. The horizontal grey dashed line is the average time to verify a transaction on the Bitcoin network, which would be compromised by a quantum attack on digital signatures.

For details about the assumptions of the model and how the overheads were calculated see: D. Aggarwal, G.K. Brennen, T. Lee, M. Santha, and M. Tomamichel, “Quantum attacks on Bitcoin, and how to protect against them,” Ledger, [S.l.], v. 3, oct. (2018).