Multi-Qubit Entangling Measurements in Linear Optics

A method for entangling a plurality of N photonic multiqubit states, wherein N is an integer greater than two, the method comprising performing a N-qubit state measurement on a set of photonic qubits, the set comprising one photonic qubit from each of the N photonic multiqubit states, wherein performing the N-qubit state measurement comprises:

• dual-rail encoding each photonic qubit of the set as probability amplitudes corresponding to the photon occupation of two orthogonal optical modes;
• providing the dual-rail encoded photonic qubits to an interferometer, the interferometer configured to:
• perform a beamsplitter interaction on the first mode of the first qubit and the second mode of the Nth qubit;
• and
• perform a beamsplitter interaction on the second mode of the jth qubit and the first mode of the (j+1)th qubit for all j between 1 and N−1, wherein j is an integer;
• and
• measuring a photon occupation of optical modes output from the interferometer.