John Martinis is currently a professor of physics at the University of California, Santa Barbara, but you probably know him best for his work on Google's quantum supremacy experiment in 2019 (https://www.nature.com/articles/s4158.... For that (and more), he won the 2021 John Stewart Bell prize for Research on Fundamental Issues in Quantum Mechanics and Their Applications.

Xanadu's Head of Hardware's answer to John's question at 23:12:

"The quality of detectors enters in two ways in our hardware architecture -- the photon counting detectors (PNRs) used to herald the the input states from which we generate GKP states, and the quadrature (homodyne) detectors that are used to actually perform measurements (and thus also gates, in our measurement-based approach) on qubits."

"The raw fidelities of both are actually quite good already - good enough for fault tolerance. For example the PNR detectors have sufficiently high resolution such that errors occur about one in a thousand times. And similarly we can get a similar resolution of quadratures, something like 0.1%, although this number is a bit harder to define."

"However, these raw numbers ignore our public enemy #1, optical loss. Including the effects of loss, the total fidelity of both these operations is poor, so poor that it’s not meaningful to really define it yet. On the bright side, once this is driven down, all the other imperfections are known to be quite small (and in most cases, any extra improvement needed, in the detectors or otherwise, is only difficult due to the presence of losses)."

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Timestamps:

0:00 Introduction
1:54 Welcome John!
9:10 Experimentalists and theoreticians
15:00 FTQC and QuEra's recent work*
19:40 The hardware zoo
30:05 Random sampling!
39:30 RSA encryption & oversight

*https://www.nature.com/articles/s4158...

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