Abstract: Generation of a non-Gaussian quantum state uses a quantum optical frequency comb source comprising at least one nonlinear optical medium and providing spectral modes including a plurality of pairs of entangled spectral modes, each pair including: a first spectral mode centered at a first frequency, and a second spectral mode entangled with the first spectral mode and centered at a second frequency that is spaced from the first frequency at a multiple of the frequency-bin spacing. Electrically controllable optical transformation modules are connected in series with a first module receiving the spectral modes. Two or more of the modules each comprise: a spectral mode phase shifter applying respective phase shifts to different spectral modes based on at least a first electrical signal, and a spectral mode mixer coupled to the spectral mode phase shifter and coupling spectral modes centered at different frequencies based on at least a second electrical signal.

Abstract: Processing codewords comprises: receiving encoded signals associated with reference signals related by quantum entanglement, where the encoded signals have been encoded with respective phases corresponding to symbols of a particular codeword; performing a first nonlinear optical process with inputs comprising a first signal derived from the encoded signals and a first signal derived from the reference signals; performing a second nonlinear optical process with inputs comprising a second signal derived from the encoded signals and a signal derived from a first output of the first nonlinear optical process; performing a first linear optical process with inputs comprising a signal derived from a second output of the first nonlinear optical process and a signal derived from a first output of the second nonlinear optical process; and processing information that includes signals derived from one or more outputs of the first linear optical process to generate an estimate of the particular codeword.

Abstract: A method for cluster-state quantum computing method includes transforming a Gaussian graph state into a non-Gaussian percolated graph state by probabilistically subtracting one photon from each of a plurality of modes forming the Gaussian graph state. The method also includes determining cat-basis qubits of the non-Gaussian percolated graph state for which one photon was successfully subtracted from a corresponding one of the modes, and identifying in the non-Gaussian percolated graph state a renormalized graph of logical qubits connected by percolation highways. The logical qubits and percolation highways are formed from the cat-basis qubits. The renormalized graph and the non-Gaussian percolated graph state are outputted to a one-way quantum computer to implementing a quantum computing algorithm.