Good luck to them, and here&#x27;s hoping that they can make some progress.<p>In case this leads to the usual &quot;what&#x27;s so hard about quantum computing that these big companies are struggling with it, and how can a small company possibly hope to beat Google?&quot; let me try to explain.<p>Quantum computers seem to do some stuff more efficiently than any classical computer can. Exact proofs are hard to come by. (The classes are BQP and BPP, with a straightforward proof that BPP is in BQP. We now have a bunch of oracles Q Such that BQP^Q &#x2F;= BPP^Q, but that&#x27;s not necessarily a proof because of course we now have oracles A and B such that P^A = NP^A but P^B &#x2F;= NP^B. So we have &quot;some evidence&quot; that quantum computers can do things faster than classical computers, but it&#x27;s not hard proof yet.) Those parenthesized concerns aside, quantum computers seem to be more efficient than classical ones at some tasks.<p>We call by the name &quot;interference&quot; this property which crucially dictates how quantum computers do stuff differently. Essentially, instead of using probabilities with real numbers between 0 and 1, quantum mechanics uses <i>scaled rotation matrices</i>, which we call &quot;amplitudes&quot; and often represent as complex numbers. We bound the scale factor between 0 and 1 and interpret its square as a probability, which yields the same result as multiplying the complex number by its complex conjugate, or multiplying the matrix by its transpose: these are all mathematically equivalent. In this framework, if the qubit |0&gt; produces an amplitude-pattern <i>f</i>(<i>z</i>) on some screen (hence you&#x27;ll see |<i>f</i>(<i>z</i>)|^2 as the pattern) and |1&gt; evolves to <i>g</i>(<i>z</i>), then the &quot;quantum superposition&quot; <i>a</i>|0&gt; + <i>b</i> |1&gt; (where <i>a</i>, <i>b</i> are complex numbers) evolves to produce the pattern |<i>a</i> <i>f</i>(<i>z</i>) + <i>b</i> <i>g</i>(<i>z</i>)|^2, which might show some sort of &quot;wavy interference pattern&quot; wherever the original patterns |<i>f</i>(<i>z</i>)|^2 and |<i>g</i>(<i>z</i>)|^2 overlap.<p>These interference effects can also be seen over multi-bit quantum states like the system <i>a</i>|00&gt; + <i>b</i>|11&gt;. In such a circumstance we call those two parts &quot;entangled&quot;, and we can prove that there is no precise quantum description which &quot;separates&quot; the two quantum-bits. However physicists have proven a crucial theorem in quantum mechanics: <i>when you look at one of those entangled-parts in isolation, it behaves according to classical probability laws</i>. This is derivable purely from the mathematics of these complex amplitudes and we usually call it &quot;tracing out&quot; the rest of the system, if you want a convenient jargon term.<p>What entangles a system with a quantum-bit? <i>Anything which interacts differently based on whether the quantum-bit is 0 or 1.</i> The intersection of these two concerns -- the universality of entanglement and the classicalness that entanglement creates -- is the thing which makes quantum computing complicated. The very interference effects which make quantum computing powerful disappear the moment that &quot;anything else&quot; entangles with our precious quantum bits: and this includes any part of the external world (so the quantum state needs to be well <i>isolated</i> from anything that is not its logic), but also the computer itself (the complicated &quot;quantum gates&quot; that we need to implement to guide the state in whatever direction it&#x27;s going). If any of those things entangle passively with the quantum state, the parts that we can measure stop showing interference effects and start acting like classical probabilistic mixtures.<p>This problem in general is called &quot;decoherence&quot; and it is the hard problem in the &quot;DiVincenzo Criteria&quot;, which are the 5 joint concerns of quantum computation. So there are basically 4 other things that you basically are not allowed to compromise to kill decoherence: (a) a qubit-centric system of states |00...0&gt;, |00...1&gt;, ... |11...1&gt;, which (b) can be initialized to a known starting state |00...0&gt;, and then (c) its qubits can be manipulated by a set of universal quantum gates, which then (d) are measured to be either 0 or 1.<p>So that&#x27;s where somebody who has a really bright insight about solving this &quot;decoherence&quot; problem could really leap light-years ahead of a bunch of highly-paid engineers and scientists who lack the crucial insight.