In superconducting quantum computers, we use mostly superconducting qubits or trapped ions. However, those systems are quite large because their environment either requires near absolute zero temperature (for superconducting to happen), or vacuum (to trap ions). Also, they need a lot of shielding from the outside world. So I was wondering why aren't we manufacturing QCs with silicon photonics, which would reduce the system size to possibly today's sizes? There is an optical equivalent to Josephson effect (since we use Josephson Junction's effect for superconducting QC) shown here, but why haven't we built more QCs around that? I get that light is harder to interfere with than electrons, so could that result in potential higher qubit error rate?

Edit: I was made aware of Xanadu, but the question still stands. Why are more companies pursuing other forms of quantum computation?


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    $\begingroup$ Reality check here: Can you explain why e.g. Xanadu's efforts or extensions of what I've laid out in this answer don't count? There are a few questions in this post, so it might make it easier to answer this if it was split into multiple posts asking for the specific details about what can/cannot be done in optical quantum computing $\endgroup$
    – Mithrandir24601
    Commented May 23, 2019 at 18:13
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    $\begingroup$ Actually, I wasn't aware of the Xanadu at all, neither have I seen your answer. Thank you very much for pointing that out. I will edit the question, but I will keep multiple questions as I feel they should remain here as it is all connected with the subject. $\endgroup$ Commented May 23, 2019 at 18:35
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    $\begingroup$ as you pointed out yourself, one of the major hurdles to overcome for optical QC is that photons do not naturally interact with each others, so you need either strong nonlinearities or other "tricks". You might be interested in this review by Terry Rudolph which explains the main problems to overcome, and how they could be solved. $\endgroup$
    – glS
    Commented May 24, 2019 at 10:31


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