Xanadu, University of Toronto and University of Waterloo have just published a very interesting blueprint explaining path to fault-tolerant quantum computing on millions of qubits with photonics. This vision provides some unique advantages for scalability, namely room-temperature computation, modularity and ease of networking together many chips.
The paper includes a concrete end-to-end architecture for the computer. All components are planar (two-dimensional integrated photonic chips used to produce a qubit cluster state in one temporal and two spatial dimensions) and most of the computer is at room temperature. Very few components require cooling, and wherever required, small commercially-available cryostats suffice. This means easier miniaturisation and fabrication via integrated photonics, and also bodes well for the cost and reliability of the device and for how fast it can be built.
The proposal enables exploiting state-of-the-art procedures for the non-deterministic generation of bosonic qubits combined with the strengths of continuous-variable quantum computation, namely the implementation of Clifford gates using easy-to-generate squeezed states.
That may allow photonics to leap-frog other platforms on the path to a quantum computer with millions of qubits. (Xanadu)
The paper can be read there.