System for converting the encoding of discrete qubits into continuous qubits

A system for converting the encoding of qubits encoded as a discrete variable into qubits encoded as a continuous variable, comprising:

• an input path of a qubit encoded as a discrete variable,
• a first squeezed vacuum state source configured to generate a single-mode squeezed vacuum state,
• a second squeezed vacuum state source configured to generate a two-mode squeezed vacuum state,
• a first beam splitter arranged to receive photons from the first squeezed vacuum state source, a first output optical path of the first beam splitter constituting an output path of a qubit encoded as a continuous variable and a second output optical path constituting a conditioning path of the first squeezed vacuum state source,
• a second, polarizing beam splitter arranged to receive photons from the second squeezed vacuum state source, a first output optical path of the second beam splitter constituting a conditioning path of the second squeezed vacuum state source and a second output optical path constituting a signal path of the second squeezed vacuum state source,
• a third beam splitter arranged on the second output optical path of the first beam splitter and on the first output optical path of the second beam splitter, configured to mix photon states of the conditioning path of the first squeezed vacuum state source and of the conditioning path of the second squeezed vacuum state source,
• a fourth beam splitter arranged on an optical path of the qubit encoded as a discrete variable and on the second output optical path of the second beam splitter, configured to mix photon states of the qubit encoded as a discrete variable and of the signal path of the second squeezed vacuum state source,
• a first photon detector arranged on a first output optical path of the third beam splitter,
• a second photon detector arranged on a first output optical path of the fourth beam splitter, the second photon detector being a photon counter,
• the system further comprising a third photon detector on a second output optical path of the third beam splitter and a fourth photon detector arranged on a second output optical path of the fourth beam splitter.