Non-gaussian photonic state engineering

A method for generating a non-Gaussian quantum state, comprising:

• generating, from a quantum optical frequency comb source comprising a nonlinear optical medium, a plurality of spectral modes that are spaced at a frequency-bin spacing and that include a plurality of pairs of entangled spectral modes, each of the plurality of pairs of entangled spectral modes including:
• a first spectral mode centered at a first frequency;
• a second spectral mode entangled with the first spectral mode and centered at a second frequency that is spaced from the first frequency by an integer multiple of the frequency-bin spacing;
• receiving, by a first module of a series of electrically controllable optical transformation modules, a plurality of spectral modes from the quantum optical frequency comb source, wherein each of two or more modules of the series of electrically controllable optical transformation modules comprises:
• a spectral mode phase shifter configured to apply phase shifts to at least some of the plurality of spectral modes, the phase shifts being based on a first electrical signal;
• and
• a spectral mode mixer coupled to the spectral mode phase shifter and configured to couple, based on a second electrical signal, spectral modes that are centered at different frequencies;
• detecting, using a plurality of photon number resolving (PNR) detectors, a first subset of the plurality of spectral modes outputted by a last module of the series of electrically controllable optical transformation modules, the first subset comprising more than one and fewer than all of the plurality of spectral modes;
• and
• outputting, via an output port, a second subset of the plurality of spectral modes outputted by the last module, the second subset comprising one or more spectral modes not detected by any of the plurality of PNR detectors.

An apparatus for generating a non-Gaussian quantum state, comprising:

• a quantum optical frequency comb source comprising at least one nonlinear optical medium and configured to provide a plurality of spectral modes spaced at a frequency-bin spacing;
• a plurality of electrically controllable optical transformation modules connected in series with a first module in the series receiving spectral modes from the quantum optical frequency comb source, where two or more of the modules each comprise:
• a spectral mode phase shifter configured to apply 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 configured to couple spectral modes centered at different frequencies based on at least a second electrical signal;
• and
• an output interface coupled to a last module in the series, the output interface including:
• a plurality of photon number resolving (PNR) detectors configured to detect respective spectral modes of more than one and fewer than all spectral modes output from the last module in the series;
• and
• at least one port providing at least one output spectral mode from the last module in the series not detected by any of the PNR detectors;
• wherein each PNR detector is configured to generate a detection signal that:
• distinguishes a detected photon number equal to zero from a detected photon number equal to one, in each of a plurality of time slots;
• and
• distinguishes a detected photon number equal to one from at least one detected photon number greater than one, in each of the plurality of time slots.