Quantum Computing, Fault Tolerance, Error Correction, Logical Qubits.
10³ − 10⁴ physical qubits in order to achieve logical error rates below 1/10¹⁴ − 1/10¹⁵” https://arxiv.org/abs/1208.0928 1,000 Although that may really mean “thousands” rather than only roughly 1,000. Day 1 opening keynote by Hartmut Neven (Google Quantum Summer Symposium 2020)