Photonic quantum computer architecture

A circuit for generating entanglement among qubits, the circuit comprising a number (N) of unit cells forming a network such that each unit cell is coupled to at least two neighboring unit cells, each unit cell comprising:

• a routing circuit having a plurality of optical paths to provide a first local resource state during a first clock cycle, a second local resource state during a second clock cycle, a third local resource state during a third clock cycle, and a fourth local resource state during a fourth clock cycle, wherein each of the first, second, third, and fourth local resource states comprises a system of entangled photonic qubits and wherein the first, second, third, and fourth clock cycles are different clock cycles;
• a plurality of fusion circuits including a first local fusion circuit, a second local fusion circuit, a third local fusion circuit, a first networked fusion circuit, and a second networked fusion circuit, each of the plurality of fusion circuits being configured to perform an entangling measurement operation between two input qubits;
• a first local delay line coupled to a first input of the first local fusion circuit and having a delay of a first number of clock cycles;
• a second local delay line coupled to a first input of the second local fusion circuit and having a delay of a second number of clock cycles, the second number being greater than the first number;
• a third local delay line coupled to a first input of the third local fusion circuit and having a delay of a third number of clock cycles, the third number being greater than the second number;
• a first routing switch configured to selectably direct a first qubit of each resource state to one of the first local delay line of the unit cell or a first input of the first networked fusion circuit of a first neighboring unit cell;
• a second routing switch configured to selectably direct a second qubit of each resource state to one of a second input of the first local fusion circuit or a second input of the first networked fusion circuit of the unit cell;
• a third routing switch configured to selectably direct a third qubit of each resource state to one of the second local delay line of the unit cell or a first input of the second networked fusion circuit of a second neighboring unit cell;
• a fourth routing switch configured to selectably direct a fourth qubit of each resource state to one of a second input of the second local fusion circuit or a second input of the second networked fusion circuit of the unit cell;
• a first routing path to direct a fifth qubit of each resource state to the third local delay line;
• and
• a second routing path to direct a sixth qubit of each resource state to the third local fusion circuit.