We&#x27;re very far from hitting any theoretical limits. We&#x27;re just hitting speed limits for silicon. Meanwhile, we already know several substrates that outperform silicon by orders of magnitude. Here are a few off top of my head:<p>graphene <a href="http:&#x2F;&#x2F;www.extremetech.com&#x2F;extreme&#x2F;175727-ibm-builds-graphene-chip-thats-10000-times-faster-using-standard-cmos-processes" rel="nofollow">http:&#x2F;&#x2F;www.extremetech.com&#x2F;extreme&#x2F;175727-ibm-builds-graphen...</a><p>spintronics: <a href="http:&#x2F;&#x2F;www.technologyreview.com&#x2F;view&#x2F;428883&#x2F;a-spintronics-breakthrough&#x2F;" rel="nofollow">http:&#x2F;&#x2F;www.technologyreview.com&#x2F;view&#x2F;428883&#x2F;a-spintronics-br...</a><p>photonics: <a href="http:&#x2F;&#x2F;www.gizmag.com&#x2F;photonic-quantum-computer-chip&#x2F;38928&#x2F;" rel="nofollow">http:&#x2F;&#x2F;www.gizmag.com&#x2F;photonic-quantum-computer-chip&#x2F;38928&#x2F;</a><p>memristors: <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Memristor" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Memristor</a><p>There&#x27;s no theoretical breakthrough needed to use these technologies, it&#x27;s simply a matter of moving them from the lab to mass production. So far there has been little incentive as companies are still squeezing out the last bits of juice from silicon, but as we start hitting the limits it&#x27;s only a matter of time until these technologies get phased in.